[Feature] Update libev to 4.33

Changelog: http://cvs.schmorp.de/libev/Changes?pathrev=rel-4_33

15 files changed, 2309 insertions, 362 deletions

diff --git a/contrib/libev/CMakeLists.txt b/contrib/libev/CMakeLists.txt
index 591166a96..e81aaee3f 100644
--- a/contrib/libev/CMakeLists.txt
+++ b/contrib/libev/CMakeLists.txt
@@ -9,8 +9,12 @@ CHECK_INCLUDE_FILES(sys/stat.h HAVE_SYS_STAT_H)
 CHECK_INCLUDE_FILES(sys/signalfd.h HAVE_SYS_SIGNALFD_H)
 CHECK_INCLUDE_FILES(port.h HAVE_PORT_H)
 CHECK_INCLUDE_FILES(poll.h HAVE_POLL_H)
+CHECK_INCLUDE_FILES(memory.h HAVE_MEMORY_H)
 CHECK_INCLUDE_FILES(sys/select.h HAVE_SYS_SELECT_H)
 CHECK_INCLUDE_FILES(sys/eventfd.h HAVE_SYS_EVENTFD_H)
+CHECK_INCLUDE_FILES(sys/timerfd.h HAVE_SYS_TIMERFD_H)
+CHECK_INCLUDE_FILES(linux/fs.h HAVE_LINUX_FS_H)
+CHECK_INCLUDE_FILES(linux/aio_abi.h HAVE_LINUX_AIO_ABI_H)
 
 IF(HAVE_SYS_INOTIFY_H)
 	CHECK_SYMBOL_EXISTS(inotify_init "sys/types.h;sys/inotify.h" HAVE_INOTIFY_INIT)
@@ -36,7 +40,9 @@ ENDIF()
 IF(HAVE_SYS_SIGNALFD_H)
 	CHECK_SYMBOL_EXISTS(signalfd sys/signalfd.h HAVE_EVENTFD)
 ENDIF()
-
+IF(HAVE_LINUX_FS_H)
+	CHECK_SYMBOL_EXISTS(RWF_SUPPORTED linux/fs.h HAVE_KERNEL_RWF_T)
+ENDIF()
 CHECK_SYMBOL_EXISTS(time.h nanosleep HAVE_NANOSLEEP)
 
 # check first without rt
diff --git a/contrib/libev/config.h.in b/contrib/libev/config.h.in
index 2bc23a75a..10fc6271a 100644
--- a/contrib/libev/config.h.in
+++ b/contrib/libev/config.h.in
@@ -24,12 +24,21 @@
 /* Define to 1 if you have the <inttypes.h> header file. */
 #cmakedefine HAVE_INTTYPES_H 1
 
+/* Define to 1 if linux/fs.h defined kernel_rwf_t */
+#cmakedefine HAVE_KERNEL_RWF_T 1
+
 /* Define to 1 if you have the `kqueue' function. */
 #cmakedefine HAVE_KQUEUE 1
 
 /* Define to 1 if you have the `rt' library (-lrt). */
 #cmakedefine HAVE_LIBRT 1
 
+/* Define to 1 if you have the <linux/aio_abi.h> header file. */
+#cmakedefine HAVE_LINUX_AIO_ABI_H 1
+
+/* Define to 1 if you have the <linux/fs.h> header file. */
+#cmakedefine HAVE_LINUX_FS_H 1
+
 /* Define to 1 if you have the <memory.h> header file. */
 #cmakedefine HAVE_MEMORY_H 1
 
@@ -87,18 +96,14 @@
 /* Define to 1 if you have the <sys/stat.h> header file. */
 #cmakedefine HAVE_SYS_STAT_H 1
 
+/* Define to 1 if you have the <sys/timerfd.h> header file. */
+#cmakedefine HAVE_SYS_TIMERFD_H 1
+
 /* Define to 1 if you have the <sys/types.h> header file. */
 #cmakedefine HAVE_SYS_TYPES_H 1
 
 /* Define to 1 if you have the <unistd.h> header file. */
 #cmakedefine HAVE_UNISTD_H 1
 
-
-/* Define to the version of this package. */
-#define PACKAGE_VERSION 4.25
-
 /* Define to 1 if you have the ANSI C header files. */
 #define STDC_HEADERS 1
-
-/* Version number of package */
-#undef VERSION
diff --git a/contrib/libev/ev.c b/contrib/libev/ev.c
index de32e1781..297fa7e1b 100644
--- a/contrib/libev/ev.c
+++ b/contrib/libev/ev.c
@@ -1,7 +1,7 @@
 /*
  * libev event processing core, watcher management
  *
- * Copyright (c) 2007-2018 Marc Alexander Lehmann <libev@schmorp.de>
+ * Copyright (c) 2007-2019 Marc Alexander Lehmann <libev@schmorp.de>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without modifica-
@@ -47,7 +47,6 @@
 
 #ifdef __GNUC__
 #pragma GCC diagnostic ignored "-Wunused-value"
-#pragma GCC diagnostic ignored "-Wstrict-aliasing"
 #endif
 
 # if HAVE_FLOOR
@@ -122,6 +121,24 @@
 #  define EV_USE_EPOLL 0
 # endif
 
+# if HAVE_LINUX_AIO_ABI_H
+#  ifndef EV_USE_LINUXAIO
+#   define EV_USE_LINUXAIO 0 /* was: EV_FEATURE_BACKENDS, always off by default */
+#  endif
+# else
+#  undef EV_USE_LINUXAIO
+#  define EV_USE_LINUXAIO 0
+# endif
+
+# if HAVE_LINUX_FS_H && HAVE_SYS_TIMERFD_H && HAVE_KERNEL_RWF_T
+#  ifndef EV_USE_IOURING
+#   define EV_USE_IOURING EV_FEATURE_BACKENDS
+#  endif
+# else
+#  undef EV_USE_IOURING
+#  define EV_USE_IOURING 0
+# endif
+
 # if HAVE_KQUEUE && HAVE_SYS_EVENT_H
 #  ifndef EV_USE_KQUEUE
 #   define EV_USE_KQUEUE EV_FEATURE_BACKENDS
@@ -167,6 +184,15 @@
 #  define EV_USE_EVENTFD 0
 # endif
 
+# if HAVE_SYS_TIMERFD_H
+#  ifndef EV_USE_TIMERFD
+#   define EV_USE_TIMERFD EV_FEATURE_OS
+#  endif
+# else
+#  undef EV_USE_TIMERFD
+#  define EV_USE_TIMERFD 0
+# endif
+
 #endif
 
 /* OS X, in its infinite idiocy, actually HARDCODES
@@ -322,6 +348,22 @@
 # define EV_USE_PORT 0
 #endif
 
+#ifndef EV_USE_LINUXAIO
+# if __linux /* libev currently assumes linux/aio_abi.h is always available on linux */
+#  define EV_USE_LINUXAIO 0 /* was: 1, always off by default */
+# else
+#  define EV_USE_LINUXAIO 0
+# endif
+#endif
+
+#ifndef EV_USE_IOURING
+# if __linux /* later checks might disable again */
+#  define EV_USE_IOURING 1
+# else
+#  define EV_USE_IOURING 0
+# endif
+#endif
+
 #ifndef EV_USE_INOTIFY
 # if __linux && (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 4))
 #  define EV_USE_INOTIFY EV_FEATURE_OS
@@ -354,6 +396,14 @@
 # endif
 #endif
 
+#ifndef EV_USE_TIMERFD
+# if __linux && (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 8))
+#  define EV_USE_TIMERFD EV_FEATURE_OS
+# else
+#  define EV_USE_TIMERFD 0
+# endif
+#endif
+
 #if 0 /* debugging */
 # define EV_VERIFY 3
 # define EV_USE_4HEAP 1
@@ -396,6 +446,7 @@
 #  define clock_gettime(id, ts) syscall (SYS_clock_gettime, (id), (ts))
 #  undef EV_USE_MONOTONIC
 #  define EV_USE_MONOTONIC 1
+#  define EV_NEED_SYSCALL 1
 # else
 #  undef EV_USE_CLOCK_SYSCALL
 #  define EV_USE_CLOCK_SYSCALL 0
@@ -419,6 +470,14 @@
 # define EV_USE_INOTIFY 0
 #endif
 
+#if __linux && EV_USE_IOURING
+# include <linux/version.h>
+# if LINUX_VERSION_CODE < KERNEL_VERSION(4,14,0)
+#  undef EV_USE_IOURING
+#  define EV_USE_IOURING 0
+# endif
+#endif
+
 #if !EV_USE_NANOSLEEP
 /* hp-ux has it in sys/time.h, which we unconditionally include above */
 # if !defined _WIN32 && !defined __hpux
@@ -426,6 +485,31 @@
 # endif
 #endif
 
+#if EV_USE_LINUXAIO
+# include <sys/syscall.h>
+# if SYS_io_getevents && EV_USE_EPOLL /* linuxaio backend requires epoll backend */
+#  define EV_NEED_SYSCALL 1
+# else
+#  undef EV_USE_LINUXAIO
+#  define EV_USE_LINUXAIO 0
+# endif
+#endif
+
+#if EV_USE_IOURING
+# include <sys/syscall.h>
+# if !SYS_io_uring_setup && __linux && !__alpha
+#  define SYS_io_uring_setup     425
+#  define SYS_io_uring_enter     426
+#  define SYS_io_uring_wregister 427
+# endif
+# if SYS_io_uring_setup && EV_USE_EPOLL /* iouring backend requires epoll backend */
+#  define EV_NEED_SYSCALL 1
+# else
+#  undef EV_USE_IOURING
+#  define EV_USE_IOURING 0
+# endif
+#endif
+
 #if EV_USE_INOTIFY
 # include <sys/statfs.h>
 # include <sys/inotify.h>
@@ -437,7 +521,7 @@
 #endif
 
 #if EV_USE_EVENTFD
-/* our minimum requirement is glibc 2.7 which has the stub, but not the header */
+/* our minimum requirement is glibc 2.7 which has the stub, but not the full header */
 # include <stdint.h>
 # ifndef EFD_NONBLOCK
 #  define EFD_NONBLOCK O_NONBLOCK
@@ -453,7 +537,7 @@ EV_CPP(extern "C") int (eventfd) (unsigned int initval, int flags);
 #endif
 
 #if EV_USE_SIGNALFD
-/* our minimum requirement is glibc 2.7 which has the stub, but not the header */
+/* our minimum requirement is glibc 2.7 which has the stub, but not the full header */
 # include <stdint.h>
 # ifndef SFD_NONBLOCK
 #  define SFD_NONBLOCK O_NONBLOCK
@@ -465,7 +549,7 @@ EV_CPP(extern "C") int (eventfd) (unsigned int initval, int flags);
 #   define SFD_CLOEXEC 02000000
 #  endif
 # endif
-EV_CPP (extern "C") int signalfd (int fd, const sigset_t *mask, int flags);
+EV_CPP (extern "C") int (signalfd) (int fd, const sigset_t *mask, int flags);
 
 struct signalfd_siginfo
 {
@@ -474,7 +558,17 @@ struct signalfd_siginfo
 };
 #endif
 
-/**/
+/* for timerfd, libev core requires TFD_TIMER_CANCEL_ON_SET &c */
+#if EV_USE_TIMERFD
+# include <sys/timerfd.h>
+/* timerfd is only used for periodics */
+# if !(defined (TFD_TIMER_CANCEL_ON_SET) && defined (TFD_CLOEXEC) && defined (TFD_NONBLOCK)) || !EV_PERIODIC_ENABLE
+#  undef EV_USE_TIMERFD
+#  define EV_USE_TIMERFD 0
+# endif
+#endif
+
+/*****************************************************************************/
 
 #if EV_VERIFY >= 3
 # define EV_FREQUENT_CHECK ev_verify (EV_A)
@@ -487,22 +581,36 @@ struct signalfd_siginfo
  * This value is good at least till the year 4000.
  */
 #define MIN_INTERVAL  0.0001220703125 /* 1/2**13, good till 4000 */
-#if 0
-#define MIN_INTERVAL  0.00000095367431640625 /* 1/2**20, good till 2200 */
+// #define MIN_INTERVAL  0.00000095367431640625 /* 1/2**20, good till 2200 */
+
+#define MIN_TIMEJUMP   1. /* minimum timejump that gets detected (if monotonic clock available) */
+#define MAX_BLOCKTIME  59.743 /* never wait longer than this time (to detect time jumps) */
+#define MAX_BLOCKTIME2 1500001.07 /* same, but when timerfd is used to detect jumps, also safe delay to not overflow */
+
+/* find a portable timestamp that is "always" in the future but fits into time_t.
+ * this is quite hard, and we are mostly guessing - we handle 32 bit signed/unsigned time_t,
+ * and sizes larger than 32 bit, and maybe the unlikely floating point time_t */
+#define EV_TSTAMP_HUGE \
+  (sizeof (time_t) >= 8     ? 10000000000000.  \
+   : 0 < (time_t)4294967295 ?     4294967295.  \
+   :                              2147483647.) \
+
+#ifndef EV_TS_CONST
+# define EV_TS_CONST(nv) nv
+# define EV_TS_TO_MSEC(a) a * 1e3 + 0.9999
+# define EV_TS_FROM_USEC(us) us * 1e-6
+# define EV_TV_SET(tv,t) do { tv.tv_sec = (long)t; tv.tv_usec = (long)((t - tv.tv_sec) * 1e6); } while (0)
+# define EV_TS_SET(ts,t) do { ts.tv_sec = (long)t; ts.tv_nsec = (long)((t - ts.tv_sec) * 1e9); } while (0)
+# define EV_TV_GET(tv) ((tv).tv_sec + (tv).tv_usec * 1e-6)
+# define EV_TS_GET(ts) ((ts).tv_sec + (ts).tv_nsec * 1e-9)
 #endif
 
-#define MIN_TIMEJUMP  1. /* minimum timejump that gets detected (if monotonic clock available) */
-#define MAX_BLOCKTIME 59.743 /* never wait longer than this time (to detect time jumps) */
-
-#define EV_TV_SET(tv,t) do { tv.tv_sec = (long)t; tv.tv_usec = (long)((t - tv.tv_sec) * 1e6); } while (0)
-#define EV_TS_SET(ts,t) do { ts.tv_sec = (long)t; ts.tv_nsec = (long)((t - ts.tv_sec) * 1e9); } while (0)
-
 /* the following is ecb.h embedded into libev - use update_ev_c to update from an external copy */
 /* ECB.H BEGIN */
 /*
  * libecb - http://software.schmorp.de/pkg/libecb
  *
- * Copyright (©) 2009-2015 Marc Alexander Lehmann <libecb@schmorp.de>
+ * Copyright (©) 2009-2015,2018-2020 Marc Alexander Lehmann <libecb@schmorp.de>
  * Copyright (©) 2011 Emanuele Giaquinta
  * All rights reserved.
  *
@@ -543,15 +651,23 @@ struct signalfd_siginfo
 #define ECB_H
 
 /* 16 bits major, 16 bits minor */
-#define ECB_VERSION 0x00010005
+#define ECB_VERSION 0x00010008
 
-#ifdef _WIN32
+#include <string.h> /* for memcpy */
+
+#if defined (_WIN32) && !defined (__MINGW32__)
   typedef   signed char   int8_t;
   typedef unsigned char  uint8_t;
+  typedef   signed char   int_fast8_t;
+  typedef unsigned char  uint_fast8_t;
   typedef   signed short  int16_t;
   typedef unsigned short uint16_t;
+  typedef   signed int    int_fast16_t;
+  typedef unsigned int   uint_fast16_t;
   typedef   signed int    int32_t;
   typedef unsigned int   uint32_t;
+  typedef   signed int    int_fast32_t;
+  typedef unsigned int   uint_fast32_t;
   #if __GNUC__
     typedef   signed long long int64_t;
     typedef unsigned long long uint64_t;
@@ -559,6 +675,8 @@ struct signalfd_siginfo
     typedef   signed __int64   int64_t;
     typedef unsigned __int64   uint64_t;
   #endif
+  typedef  int64_t  int_fast64_t;
+  typedef uint64_t uint_fast64_t;
   #ifdef _WIN64
     #define ECB_PTRSIZE 8
     typedef uint64_t uintptr_t;
@@ -580,6 +698,14 @@ struct signalfd_siginfo
 #define ECB_GCC_AMD64 (__amd64 || __amd64__ || __x86_64 || __x86_64__)
 #define ECB_MSVC_AMD64 (_M_AMD64 || _M_X64)
 
+#ifndef ECB_OPTIMIZE_SIZE
+  #if __OPTIMIZE_SIZE__
+    #define ECB_OPTIMIZE_SIZE 1
+  #else
+    #define ECB_OPTIMIZE_SIZE 0
+  #endif
+#endif
+
 /* work around x32 idiocy by defining proper macros */
 #if ECB_GCC_AMD64 || ECB_MSVC_AMD64
   #if _ILP32
@@ -667,6 +793,7 @@ struct signalfd_siginfo
 
 #ifndef ECB_MEMORY_FENCE
   #if ECB_GCC_VERSION(2,5) || defined __INTEL_COMPILER || (__llvm__ && __GNUC__) || __SUNPRO_C >= 0x5110 || __SUNPRO_CC >= 0x5110
+    #define ECB_MEMORY_FENCE_RELAXED __asm__ __volatile__ ("" : : : "memory")
     #if __i386 || __i386__
       #define ECB_MEMORY_FENCE         __asm__ __volatile__ ("lock; orb $0, -1(%%esp)" : : : "memory")
       #define ECB_MEMORY_FENCE_ACQUIRE __asm__ __volatile__ (""                        : : : "memory")
@@ -726,12 +853,14 @@ struct signalfd_siginfo
     #define ECB_MEMORY_FENCE         __atomic_thread_fence (__ATOMIC_SEQ_CST)
     #define ECB_MEMORY_FENCE_ACQUIRE __atomic_thread_fence (__ATOMIC_ACQUIRE)
     #define ECB_MEMORY_FENCE_RELEASE __atomic_thread_fence (__ATOMIC_RELEASE)
+    #define ECB_MEMORY_FENCE_RELAXED __atomic_thread_fence (__ATOMIC_RELAXED)
 
   #elif ECB_CLANG_EXTENSION(c_atomic)
     /* see comment below (stdatomic.h) about the C11 memory model. */
     #define ECB_MEMORY_FENCE         __c11_atomic_thread_fence (__ATOMIC_SEQ_CST)
     #define ECB_MEMORY_FENCE_ACQUIRE __c11_atomic_thread_fence (__ATOMIC_ACQUIRE)
     #define ECB_MEMORY_FENCE_RELEASE __c11_atomic_thread_fence (__ATOMIC_RELEASE)
+    #define ECB_MEMORY_FENCE_RELAXED __c11_atomic_thread_fence (__ATOMIC_RELAXED)
 
   #elif ECB_GCC_VERSION(4,4) || defined __INTEL_COMPILER || defined __clang__
     #define ECB_MEMORY_FENCE         __sync_synchronize ()
@@ -751,9 +880,10 @@ struct signalfd_siginfo
     #define ECB_MEMORY_FENCE         MemoryBarrier () /* actually just xchg on x86... scary */
   #elif __SUNPRO_C >= 0x5110 || __SUNPRO_CC >= 0x5110
     #include <mbarrier.h>
-    #define ECB_MEMORY_FENCE         __machine_rw_barrier ()
-    #define ECB_MEMORY_FENCE_ACQUIRE __machine_r_barrier  ()
-    #define ECB_MEMORY_FENCE_RELEASE __machine_w_barrier  ()
+    #define ECB_MEMORY_FENCE         __machine_rw_barrier  ()
+    #define ECB_MEMORY_FENCE_ACQUIRE __machine_acq_barrier ()
+    #define ECB_MEMORY_FENCE_RELEASE __machine_rel_barrier ()
+    #define ECB_MEMORY_FENCE_RELAXED __compiler_barrier ()
   #elif __xlC__
     #define ECB_MEMORY_FENCE         __sync ()
   #endif
@@ -764,15 +894,9 @@ struct signalfd_siginfo
     /* we assume that these memory fences work on all variables/all memory accesses, */
     /* not just C11 atomics and atomic accesses */
     #include <stdatomic.h>
-    /* Unfortunately, neither gcc 4.7 nor clang 3.1 generate any instructions for */
-    /* any fence other than seq_cst, which isn't very efficient for us. */
-    /* Why that is, we don't know - either the C11 memory model is quite useless */
-    /* for most usages, or gcc and clang have a bug */
-    /* I *currently* lean towards the latter, and inefficiently implement */
-    /* all three of ecb's fences as a seq_cst fence */
-    /* Update, gcc-4.8 generates mfence for all c++ fences, but nothing */
-    /* for all __atomic_thread_fence's except seq_cst */
     #define ECB_MEMORY_FENCE         atomic_thread_fence (memory_order_seq_cst)
+    #define ECB_MEMORY_FENCE_ACQUIRE atomic_thread_fence (memory_order_acquire)
+    #define ECB_MEMORY_FENCE_RELEASE atomic_thread_fence (memory_order_release)
   #endif
 #endif
 
@@ -802,6 +926,10 @@ struct signalfd_siginfo
   #define ECB_MEMORY_FENCE_RELEASE ECB_MEMORY_FENCE
 #endif
 
+#if !defined ECB_MEMORY_FENCE_RELAXED && defined ECB_MEMORY_FENCE
+  #define ECB_MEMORY_FENCE_RELAXED ECB_MEMORY_FENCE /* very heavy-handed */
+#endif
+
 /*****************************************************************************/
 
 #if ECB_CPP
@@ -1093,6 +1221,44 @@ ecb_inline ecb_const uint32_t ecb_rotr32 (uint32_t x, unsigned int count) { retu
 ecb_inline ecb_const uint64_t ecb_rotl64 (uint64_t x, unsigned int count) { return (x >> (64 - count)) | (x << count); }
 ecb_inline ecb_const uint64_t ecb_rotr64 (uint64_t x, unsigned int count) { return (x << (64 - count)) | (x >> count); }
 
+#if ECB_CPP
+
+inline uint8_t  ecb_ctz (uint8_t  v) { return ecb_ctz32 (v); }
+inline uint16_t ecb_ctz (uint16_t v) { return ecb_ctz32 (v); }
+inline uint32_t ecb_ctz (uint32_t v) { return ecb_ctz32 (v); }
+inline uint64_t ecb_ctz (uint64_t v) { return ecb_ctz64 (v); }
+
+inline bool ecb_is_pot (uint8_t  v) { return ecb_is_pot32 (v); }
+inline bool ecb_is_pot (uint16_t v) { return ecb_is_pot32 (v); }
+inline bool ecb_is_pot (uint32_t v) { return ecb_is_pot32 (v); }
+inline bool ecb_is_pot (uint64_t v) { return ecb_is_pot64 (v); }
+
+inline int ecb_ld (uint8_t  v) { return ecb_ld32 (v); }
+inline int ecb_ld (uint16_t v) { return ecb_ld32 (v); }
+inline int ecb_ld (uint32_t v) { return ecb_ld32 (v); }
+inline int ecb_ld (uint64_t v) { return ecb_ld64 (v); }
+
+inline int ecb_popcount (uint8_t  v) { return ecb_popcount32 (v); }
+inline int ecb_popcount (uint16_t v) { return ecb_popcount32 (v); }
+inline int ecb_popcount (uint32_t v) { return ecb_popcount32 (v); }
+inline int ecb_popcount (uint64_t v) { return ecb_popcount64 (v); }
+
+inline uint8_t  ecb_bitrev (uint8_t  v) { return ecb_bitrev8  (v); }
+inline uint16_t ecb_bitrev (uint16_t v) { return ecb_bitrev16 (v); }
+inline uint32_t ecb_bitrev (uint32_t v) { return ecb_bitrev32 (v); }
+
+inline uint8_t  ecb_rotl (uint8_t  v, unsigned int count) { return ecb_rotl8  (v, count); }
+inline uint16_t ecb_rotl (uint16_t v, unsigned int count) { return ecb_rotl16 (v, count); }
+inline uint32_t ecb_rotl (uint32_t v, unsigned int count) { return ecb_rotl32 (v, count); }
+inline uint64_t ecb_rotl (uint64_t v, unsigned int count) { return ecb_rotl64 (v, count); }
+
+inline uint8_t  ecb_rotr (uint8_t  v, unsigned int count) { return ecb_rotr8  (v, count); }
+inline uint16_t ecb_rotr (uint16_t v, unsigned int count) { return ecb_rotr16 (v, count); }
+inline uint32_t ecb_rotr (uint32_t v, unsigned int count) { return ecb_rotr32 (v, count); }
+inline uint64_t ecb_rotr (uint64_t v, unsigned int count) { return ecb_rotr64 (v, count); }
+
+#endif
+
 #if ECB_GCC_VERSION(4,3) || (ECB_CLANG_BUILTIN(__builtin_bswap32) && ECB_CLANG_BUILTIN(__builtin_bswap64))
   #if ECB_GCC_VERSION(4,8) || ECB_CLANG_BUILTIN(__builtin_bswap16)
   #define ecb_bswap16(x)  __builtin_bswap16 (x)
@@ -1173,6 +1339,78 @@ ecb_inline ecb_const ecb_bool ecb_big_endian    (void) { return ecb_byteorder_he
 ecb_inline ecb_const ecb_bool ecb_little_endian (void);
 ecb_inline ecb_const ecb_bool ecb_little_endian (void) { return ecb_byteorder_helper () == 0x44332211; }
 
+/*****************************************************************************/
+/* unaligned load/store */
+
+ecb_inline uint_fast16_t ecb_be_u16_to_host (uint_fast16_t v) { return ecb_little_endian () ? ecb_bswap16 (v) : v; }
+ecb_inline uint_fast32_t ecb_be_u32_to_host (uint_fast32_t v) { return ecb_little_endian () ? ecb_bswap32 (v) : v; }
+ecb_inline uint_fast64_t ecb_be_u64_to_host (uint_fast64_t v) { return ecb_little_endian () ? ecb_bswap64 (v) : v; }
+
+ecb_inline uint_fast16_t ecb_le_u16_to_host (uint_fast16_t v) { return ecb_big_endian    () ? ecb_bswap16 (v) : v; }
+ecb_inline uint_fast32_t ecb_le_u32_to_host (uint_fast32_t v) { return ecb_big_endian    () ? ecb_bswap32 (v) : v; }
+ecb_inline uint_fast64_t ecb_le_u64_to_host (uint_fast64_t v) { return ecb_big_endian    () ? ecb_bswap64 (v) : v; }
+
+ecb_inline uint_fast16_t ecb_peek_u16_u (const void *ptr) { uint16_t v; memcpy (&v, ptr, sizeof (v)); return v; }
+ecb_inline uint_fast32_t ecb_peek_u32_u (const void *ptr) { uint32_t v; memcpy (&v, ptr, sizeof (v)); return v; }
+ecb_inline uint_fast64_t ecb_peek_u64_u (const void *ptr) { uint64_t v; memcpy (&v, ptr, sizeof (v)); return v; }
+
+ecb_inline uint_fast16_t ecb_peek_be_u16_u (const void *ptr) { return ecb_be_u16_to_host (ecb_peek_u16_u (ptr)); }
+ecb_inline uint_fast32_t ecb_peek_be_u32_u (const void *ptr) { return ecb_be_u32_to_host (ecb_peek_u32_u (ptr)); }
+ecb_inline uint_fast64_t ecb_peek_be_u64_u (const void *ptr) { return ecb_be_u64_to_host (ecb_peek_u64_u (ptr)); }
+
+ecb_inline uint_fast16_t ecb_peek_le_u16_u (const void *ptr) { return ecb_le_u16_to_host (ecb_peek_u16_u (ptr)); }
+ecb_inline uint_fast32_t ecb_peek_le_u32_u (const void *ptr) { return ecb_le_u32_to_host (ecb_peek_u32_u (ptr)); }
+ecb_inline uint_fast64_t ecb_peek_le_u64_u (const void *ptr) { return ecb_le_u64_to_host (ecb_peek_u64_u (ptr)); }
+
+ecb_inline uint_fast16_t ecb_host_to_be_u16 (uint_fast16_t v) { return ecb_little_endian () ? ecb_bswap16 (v) : v; }
+ecb_inline uint_fast32_t ecb_host_to_be_u32 (uint_fast32_t v) { return ecb_little_endian () ? ecb_bswap32 (v) : v; }
+ecb_inline uint_fast64_t ecb_host_to_be_u64 (uint_fast64_t v) { return ecb_little_endian () ? ecb_bswap64 (v) : v; }
+
+ecb_inline uint_fast16_t ecb_host_to_le_u16 (uint_fast16_t v) { return ecb_big_endian    () ? ecb_bswap16 (v) : v; }
+ecb_inline uint_fast32_t ecb_host_to_le_u32 (uint_fast32_t v) { return ecb_big_endian    () ? ecb_bswap32 (v) : v; }
+ecb_inline uint_fast64_t ecb_host_to_le_u64 (uint_fast64_t v) { return ecb_big_endian    () ? ecb_bswap64 (v) : v; }
+
+ecb_inline void ecb_poke_u16_u (void *ptr, uint16_t v) { memcpy (ptr, &v, sizeof (v)); }
+ecb_inline void ecb_poke_u32_u (void *ptr, uint32_t v) { memcpy (ptr, &v, sizeof (v)); }
+ecb_inline void ecb_poke_u64_u (void *ptr, uint64_t v) { memcpy (ptr, &v, sizeof (v)); }
+
+ecb_inline void ecb_poke_be_u16_u (void *ptr, uint_fast16_t v) { ecb_poke_u16_u (ptr, ecb_host_to_be_u16 (v)); }
+ecb_inline void ecb_poke_be_u32_u (void *ptr, uint_fast32_t v) { ecb_poke_u32_u (ptr, ecb_host_to_be_u32 (v)); }
+ecb_inline void ecb_poke_be_u64_u (void *ptr, uint_fast64_t v) { ecb_poke_u64_u (ptr, ecb_host_to_be_u64 (v)); }
+
+ecb_inline void ecb_poke_le_u16_u (void *ptr, uint_fast16_t v) { ecb_poke_u16_u (ptr, ecb_host_to_le_u16 (v)); }
+ecb_inline void ecb_poke_le_u32_u (void *ptr, uint_fast32_t v) { ecb_poke_u32_u (ptr, ecb_host_to_le_u32 (v)); }
+ecb_inline void ecb_poke_le_u64_u (void *ptr, uint_fast64_t v) { ecb_poke_u64_u (ptr, ecb_host_to_le_u64 (v)); }
+
+#if ECB_CPP
+
+inline uint8_t  ecb_bswap (uint8_t  v) { return v; }
+inline uint16_t ecb_bswap (uint16_t v) { return ecb_bswap16 (v); }
+inline uint32_t ecb_bswap (uint32_t v) { return ecb_bswap32 (v); }
+inline uint64_t ecb_bswap (uint64_t v) { return ecb_bswap64 (v); }
+
+template<typename T> inline T ecb_be_to_host (T v) { return ecb_little_endian () ? ecb_bswap (v) : v; }
+template<typename T> inline T ecb_le_to_host (T v) { return ecb_big_endian    () ? ecb_bswap (v) : v; }
+template<typename T> inline T ecb_peek       (const void *ptr) { return *(const T *)ptr; }
+template<typename T> inline T ecb_peek_be    (const void *ptr) { return ecb_be_to_host (ecb_peek  <T> (ptr)); }
+template<typename T> inline T ecb_peek_le    (const void *ptr) { return ecb_le_to_host (ecb_peek  <T> (ptr)); }
+template<typename T> inline T ecb_peek_u     (const void *ptr) { T v; memcpy (&v, ptr, sizeof (v)); return v; }
+template<typename T> inline T ecb_peek_be_u  (const void *ptr) { return ecb_be_to_host (ecb_peek_u<T> (ptr)); }
+template<typename T> inline T ecb_peek_le_u  (const void *ptr) { return ecb_le_to_host (ecb_peek_u<T> (ptr)); }
+
+template<typename T> inline T ecb_host_to_be (T v) { return ecb_little_endian () ? ecb_bswap (v) : v; }
+template<typename T> inline T ecb_host_to_le (T v) { return ecb_big_endian    () ? ecb_bswap (v) : v; }
+template<typename T> inline void ecb_poke      (void *ptr, T v) { *(T *)ptr = v; }
+template<typename T> inline void ecb_poke_be   (void *ptr, T v) { return ecb_poke  <T> (ptr, ecb_host_to_be (v)); }
+template<typename T> inline void ecb_poke_le   (void *ptr, T v) { return ecb_poke  <T> (ptr, ecb_host_to_le (v)); }
+template<typename T> inline void ecb_poke_u    (void *ptr, T v) { memcpy (ptr, &v, sizeof (v)); }
+template<typename T> inline void ecb_poke_be_u (void *ptr, T v) { return ecb_poke_u<T> (ptr, ecb_host_to_be (v)); }
+template<typename T> inline void ecb_poke_le_u (void *ptr, T v) { return ecb_poke_u<T> (ptr, ecb_host_to_le (v)); }
+
+#endif
+
+/*****************************************************************************/
+
 #if ECB_GCC_VERSION(3,0) || ECB_C99
   #define ecb_mod(m,n) ((m) % (n) + ((m) % (n) < 0 ? (n) : 0))
 #else
@@ -1206,6 +1444,8 @@ ecb_inline ecb_const ecb_bool ecb_little_endian (void) { return ecb_byteorder_he
   #define ecb_array_length(name) (sizeof (name) / sizeof (name [0]))
 #endif
 
+/*****************************************************************************/
+
 ecb_function_ ecb_const uint32_t ecb_binary16_to_binary32 (uint32_t x);
 ecb_function_ ecb_const uint32_t
 ecb_binary16_to_binary32 (uint32_t x)
@@ -1323,7 +1563,6 @@ ecb_binary32_to_binary16 (uint32_t x)
     || (defined __arm__ && (defined __ARM_EABI__ || defined __EABI__ || defined __VFP_FP__ || defined _WIN32_WCE || defined __ANDROID__)) \
     || defined __aarch64__
   #define ECB_STDFP 1
-  #include <string.h> /* for memcpy */
 #else
   #define ECB_STDFP 0
 #endif
@@ -1518,7 +1757,7 @@ ecb_binary32_to_binary16 (uint32_t x)
 #if ECB_MEMORY_FENCE_NEEDS_PTHREADS
 /* if your architecture doesn't need memory fences, e.g. because it is
  * single-cpu/core, or if you use libev in a project that doesn't use libev
- * from multiple threads, then you can define ECB_AVOID_PTHREADS when compiling
+ * from multiple threads, then you can define ECB_NO_THREADS when compiling
  * libev, in which cases the memory fences become nops.
  * alternatively, you can remove this #error and link against libpthread,
  * which will then provide the memory fences.
@@ -1532,18 +1771,80 @@ ecb_binary32_to_binary16 (uint32_t x)
 # define ECB_MEMORY_FENCE_RELEASE ECB_MEMORY_FENCE
 #endif
 
-#define expect_false(cond) ecb_expect_false (cond)
-#define expect_true(cond)  ecb_expect_true  (cond)
-#define noinline           ecb_noinline
-
 #define inline_size        ecb_inline
 
 #if EV_FEATURE_CODE
 # define inline_speed      ecb_inline
 #else
-# define inline_speed      noinline static
+# define inline_speed      ecb_noinline static
+#endif
+
+/*****************************************************************************/
+/* raw syscall wrappers */
+
+#if EV_NEED_SYSCALL
+
+#include <sys/syscall.h>
+
+/*
+ * define some syscall wrappers for common architectures
+ * this is mostly for nice looks during debugging, not performance.
+ * our syscalls return < 0, not == -1, on error. which is good
+ * enough for linux aio.
+ * TODO: arm is also common nowadays, maybe even mips and x86
+ * TODO: after implementing this, it suddenly looks like overkill, but its hard to remove...
+ */
+#if __GNUC__ && __linux && ECB_AMD64 && !EV_FEATURE_CODE
+  /* the costly errno access probably kills this for size optimisation */
+
+  #define ev_syscall(nr,narg,arg1,arg2,arg3,arg4,arg5,arg6)            \
+    ({                                                                 \
+        long res;                                                      \
+        register unsigned long r6 __asm__ ("r9" );                     \
+        register unsigned long r5 __asm__ ("r8" );                     \
+        register unsigned long r4 __asm__ ("r10");                     \
+        register unsigned long r3 __asm__ ("rdx");                     \
+        register unsigned long r2 __asm__ ("rsi");                     \
+        register unsigned long r1 __asm__ ("rdi");                     \
+        if (narg >= 6) r6 = (unsigned long)(arg6);                     \
+        if (narg >= 5) r5 = (unsigned long)(arg5);                     \
+        if (narg >= 4) r4 = (unsigned long)(arg4);                     \
+        if (narg >= 3) r3 = (unsigned long)(arg3);                     \
+        if (narg >= 2) r2 = (unsigned long)(arg2);                     \
+        if (narg >= 1) r1 = (unsigned long)(arg1);                     \
+        __asm__ __volatile__ (                                         \
+          "syscall\n\t"                                                \
+          : "=a" (res)                                                 \
+          : "0" (nr), "r" (r1), "r" (r2), "r" (r3), "r" (r4), "r" (r5) \
+          : "cc", "r11", "cx", "memory");                              \
+        errno = -res;                                                  \
+        res;                                                           \
+    })
+
+#endif
+
+#ifdef ev_syscall
+  #define ev_syscall0(nr)                               ev_syscall (nr, 0,    0,    0,    0,    0,    0,   0)
+  #define ev_syscall1(nr,arg1)                          ev_syscall (nr, 1, arg1,    0,    0,    0,    0,   0)
+  #define ev_syscall2(nr,arg1,arg2)                     ev_syscall (nr, 2, arg1, arg2,    0,    0,    0,   0)
+  #define ev_syscall3(nr,arg1,arg2,arg3)                ev_syscall (nr, 3, arg1, arg2, arg3,    0,    0,   0)
+  #define ev_syscall4(nr,arg1,arg2,arg3,arg4)           ev_syscall (nr, 3, arg1, arg2, arg3, arg4,    0,   0)
+  #define ev_syscall5(nr,arg1,arg2,arg3,arg4,arg5)      ev_syscall (nr, 5, arg1, arg2, arg3, arg4, arg5,   0)
+  #define ev_syscall6(nr,arg1,arg2,arg3,arg4,arg5,arg6) ev_syscall (nr, 6, arg1, arg2, arg3, arg4, arg5,arg6)
+#else
+  #define ev_syscall0(nr)                               syscall (nr)
+  #define ev_syscall1(nr,arg1)                          syscall (nr, arg1)
+  #define ev_syscall2(nr,arg1,arg2)                     syscall (nr, arg1, arg2)
+  #define ev_syscall3(nr,arg1,arg2,arg3)                syscall (nr, arg1, arg2, arg3)
+  #define ev_syscall4(nr,arg1,arg2,arg3,arg4)           syscall (nr, arg1, arg2, arg3, arg4)
+  #define ev_syscall5(nr,arg1,arg2,arg3,arg4,arg5)      syscall (nr, arg1, arg2, arg3, arg4, arg5)
+  #define ev_syscall6(nr,arg1,arg2,arg3,arg4,arg5,arg6) syscall (nr, arg1, arg2, arg3, arg4, arg5,arg6)
 #endif
 
+#endif
+
+/*****************************************************************************/
+
 #define NUMPRI (EV_MAXPRI - EV_MINPRI + 1)
 
 #if EV_MINPRI == EV_MAXPRI
@@ -1552,8 +1853,7 @@ ecb_binary32_to_binary16 (uint32_t x)
 # define ABSPRI(w) (((W)w)->priority - EV_MINPRI)
 #endif
 
-#define EMPTY       /* required for microsofts broken pseudo-c compiler */
-#define EMPTY2(a,b) /* used to suppress some warnings */
+#define EMPTY /* required for microsofts broken pseudo-c compiler */
 
 typedef ev_watcher *W;
 typedef ev_watcher_list *WL;
@@ -1590,6 +1890,10 @@ static EV_ATOMIC_T have_cheap_timer = 0;
 
 /*****************************************************************************/
 
+#if EV_USE_LINUXAIO
+# include <linux/aio_abi.h> /* probably only needed for aio_context_t */
+#endif
+
 /* define a suitable floor function (only used by periodics atm) */
 
 #if EV_USE_FLOOR
@@ -1600,7 +1904,7 @@ static EV_ATOMIC_T have_cheap_timer = 0;
 #include <float.h>
 
 /* a floor() replacement function, should be independent of ev_tstamp type */
-noinline
+ecb_noinline
 static ev_tstamp
 ev_floor (ev_tstamp v)
 {
@@ -1611,26 +1915,26 @@ ev_floor (ev_tstamp v)
   const ev_tstamp shift = sizeof (unsigned long) >= 8 ? 18446744073709551616. : 4294967296.;
 #endif
 
-  /* argument too large for an unsigned long? */
-  if (expect_false (v >= shift))
+  /* special treatment for negative arguments */
+  if (ecb_expect_false (v < 0.))
+    {
+      ev_tstamp f = -ev_floor (-v);
+
+      return f - (f == v ? 0 : 1);
+    }
+
+  /* argument too large for an unsigned long? then reduce it */
+  if (ecb_expect_false (v >= shift))
     {
       ev_tstamp f;
 
       if (v == v - 1.)
-        return v; /* very large number */
+        return v; /* very large numbers are assumed to be integer */
 
       f = shift * ev_floor (v * (1. / shift));
       return f + ev_floor (v - f);
     }
 
-  /* special treatment for negative args? */
-  if (expect_false (v < 0.))
-    {
-      ev_tstamp f = -ev_floor (-v);
-
-      return f - (f == v ? 0 : 1);
-    }
-
   /* fits into an unsigned long */
   return (unsigned long)v;
 }
@@ -1643,7 +1947,7 @@ ev_floor (ev_tstamp v)
 # include <sys/utsname.h>
 #endif
 
-noinline ecb_cold
+ecb_noinline ecb_cold
 static unsigned int
 ev_linux_version (void)
 {
@@ -1683,7 +1987,7 @@ ev_linux_version (void)
 /*****************************************************************************/
 
 #if EV_AVOID_STDIO
-noinline ecb_cold
+ecb_noinline ecb_cold
 static void
 ev_printerr (const char *msg)
 {
@@ -1700,7 +2004,7 @@ ev_set_syserr_cb (void (*cb)(const char *msg) EV_NOEXCEPT) EV_NOEXCEPT
   syserr_cb = cb;
 }
 
-noinline ecb_cold
+ecb_noinline ecb_cold
 static void
 ev_syserr (const char *msg)
 {
@@ -1781,8 +2085,8 @@ typedef struct
   WL head;
   unsigned char events; /* the events watched for */
   unsigned char reify;  /* flag set when this ANFD needs reification (EV_ANFD_REIFY, EV__IOFDSET) */
-  unsigned char emask;  /* the epoll backend stores the actual kernel mask in here */
-  unsigned char unused;
+  unsigned char emask;  /* some backends store the actual kernel mask in here */
+  unsigned char eflags; /* flags field for use by backends */
 #if EV_USE_EPOLL
   unsigned int egen;    /* generation counter to counter epoll bugs */
 #endif
@@ -1842,10 +2146,11 @@ typedef struct
   #include "ev_wrap.h"
 
   static struct ev_loop default_loop_struct;
-  static struct ev_loop *ev_default_loop_ptr = 0;
+  EV_API_DECL struct ev_loop *ev_default_loop_ptr = 0; /* needs to be initialised to make it a definition despite extern */
+
 #else
 
-  EV_API_DECL ev_tstamp ev_rt_now = 0; /* needs to be initialised to make it a definition despite extern */
+  EV_API_DECL ev_tstamp ev_rt_now = EV_TS_CONST (0.); /* needs to be initialised to make it a definition despite extern */
   #define VAR(name,decl) static decl;
     #include "ev_vars.h"
   #undef VAR
@@ -1855,8 +2160,8 @@ typedef struct
 #endif
 
 #if EV_FEATURE_API
-# define EV_RELEASE_CB if (expect_false (release_cb)) release_cb (EV_A)
-# define EV_ACQUIRE_CB if (expect_false (acquire_cb)) acquire_cb (EV_A)
+# define EV_RELEASE_CB if (ecb_expect_false (release_cb)) release_cb (EV_A)
+# define EV_ACQUIRE_CB if (ecb_expect_false (acquire_cb)) acquire_cb (EV_A)
 # define EV_INVOKE_PENDING invoke_cb (EV_A)
 #else
 # define EV_RELEASE_CB (void)0
@@ -1873,17 +2178,19 @@ ev_tstamp
 ev_time (void) EV_NOEXCEPT
 {
 #if EV_USE_REALTIME
-  if (expect_true (have_realtime))
+  if (ecb_expect_true (have_realtime))
     {
       struct timespec ts;
       clock_gettime (CLOCK_REALTIME, &ts);
-      return ts.tv_sec + ts.tv_nsec * 1e-9;
+      return EV_TS_GET (ts);
     }
 #endif
 
-  struct timeval tv;
-  gettimeofday (&tv, 0);
-  return tv.tv_sec + tv.tv_usec * 1e-6;
+  {
+    struct timeval tv;
+    gettimeofday (&tv, 0);
+    return EV_TV_GET (tv);
+  }
 }
 #endif
 
@@ -1891,11 +2198,11 @@ inline_size ev_tstamp
 get_clock (void)
 {
 #if EV_USE_MONOTONIC
-  if (expect_true (have_monotonic))
+  if (ecb_expect_true (have_monotonic))
     {
       struct timespec ts;
       clock_gettime (monotinic_clock_id, &ts);
-      return ts.tv_sec + ts.tv_nsec * 1e-9;
+      return ((ev_tstamp)ts.tv_sec) + ts.tv_nsec * 1e-9;
     }
 #endif
 
@@ -1913,7 +2220,7 @@ ev_now (EV_P) EV_NOEXCEPT
 void
 ev_sleep (ev_tstamp delay) EV_NOEXCEPT
 {
-  if (delay > 0.)
+  if (delay > EV_TS_CONST (0.))
     {
 #if EV_USE_NANOSLEEP
       struct timespec ts;
@@ -1923,7 +2230,7 @@ ev_sleep (ev_tstamp delay) EV_NOEXCEPT
 #elif defined _WIN32
       /* maybe this should round up, as ms is very low resolution */
       /* compared to select (µs) or nanosleep (ns) */
-      Sleep ((unsigned long)(delay * 1e3));
+      Sleep ((unsigned long)(EV_TS_TO_MSEC (delay)));
 #else
       struct timeval tv;
 
@@ -1963,7 +2270,7 @@ array_nextsize (int elem, int cur, int cnt)
   return ncur;
 }
 
-noinline ecb_cold
+ecb_noinline ecb_cold
 static void *
 array_realloc (int elem, void *base, int *cur, int cnt)
 {
@@ -1971,16 +2278,18 @@ array_realloc (int elem, void *base, int *cur, int cnt)
   return ev_realloc (base, elem * *cur);
 }
 
-#define array_init_zero(base,count)	\
-  memset ((void *)(base), 0, sizeof (*(base)) * (count))
+#define array_needsize_noinit(base,offset,count)
+
+#define array_needsize_zerofill(base,offset,count)	\
+  memset ((void *)(base + offset), 0, sizeof (*(base)) * (count))
 
 #define array_needsize(type,base,cur,cnt,init)			\
-  if (expect_false ((cnt) > (cur)))				\
+  if (ecb_expect_false ((cnt) > (cur)))				\
     {								\
       ecb_unused int ocur_ = (cur);				\
       (base) = (type *)array_realloc				\
          (sizeof (type), (base), &(cur), (cnt));		\
-      init ((base) + (ocur_), (cur) - ocur_);			\
+      init ((base), ocur_, ((cur) - ocur_));			\
     }
 
 #if 0
@@ -1999,25 +2308,25 @@ array_realloc (int elem, void *base, int *cur, int cnt)
 /*****************************************************************************/
 
 /* dummy callback for pending events */
-noinline
+ecb_noinline
 static void
 pendingcb (EV_P_ ev_prepare *w, int revents)
 {
 }
 
-noinline
+ecb_noinline
 void
 ev_feed_event (EV_P_ void *w, int revents) EV_NOEXCEPT
 {
   W w_ = (W)w;
   int pri = ABSPRI (w_);
 
-  if (expect_false (w_->pending))
+  if (ecb_expect_false (w_->pending))
     pendings [pri][w_->pending - 1].events |= revents;
   else
     {
       w_->pending = ++pendingcnt [pri];
-      array_needsize (ANPENDING, pendings [pri], pendingmax [pri], w_->pending, EMPTY2);
+      array_needsize (ANPENDING, pendings [pri], pendingmax [pri], w_->pending, array_needsize_noinit);
       pendings [pri][w_->pending - 1].w      = w_;
       pendings [pri][w_->pending - 1].events = revents;
     }
@@ -2028,7 +2337,7 @@ ev_feed_event (EV_P_ void *w, int revents) EV_NOEXCEPT
 inline_speed void
 feed_reverse (EV_P_ W w)
 {
-  array_needsize (W, rfeeds, rfeedmax, rfeedcnt + 1, EMPTY2);
+  array_needsize (W, rfeeds, rfeedmax, rfeedcnt + 1, array_needsize_noinit);
   rfeeds [rfeedcnt++] = w;
 }
 
@@ -2073,7 +2382,7 @@ fd_event (EV_P_ int fd, int revents)
 {
   ANFD *anfd = anfds + fd;
 
-  if (expect_true (!anfd->reify))
+  if (ecb_expect_true (!anfd->reify))
     fd_event_nocheck (EV_A_ fd, revents);
 }
 
@@ -2091,8 +2400,20 @@ fd_reify (EV_P)
 {
   int i;
 
+  /* most backends do not modify the fdchanges list in backend_modfiy.
+   * except io_uring, which has fixed-size buffers which might force us
+   * to handle events in backend_modify, causing fdchanges to be amended,
+   * which could result in an endless loop.
+   * to avoid this, we do not dynamically handle fds that were added
+   * during fd_reify. that means that for those backends, fdchangecnt
+   * might be non-zero during poll, which must cause them to not block.
+   * to not put too much of a burden on other backends, this detail
+   * needs to be handled in the backend.
+   */
+  int changecnt = fdchangecnt;
+
 #if EV_SELECT_IS_WINSOCKET || EV_USE_IOCP
-  for (i = 0; i < fdchangecnt; ++i)
+  for (i = 0; i < changecnt; ++i)
     {
       int fd = fdchanges [i];
       ANFD *anfd = anfds + fd;
@@ -2116,7 +2437,7 @@ fd_reify (EV_P)
     }
 #endif
 
-  for (i = 0; i < fdchangecnt; ++i)
+  for (i = 0; i < changecnt; ++i)
     {
       int fd = fdchanges [i];
       ANFD *anfd = anfds + fd;
@@ -2125,9 +2446,9 @@ fd_reify (EV_P)
       unsigned char o_events = anfd->events;
       unsigned char o_reify  = anfd->reify;
 
-      anfd->reify  = 0;
+      anfd->reify = 0;
 
-      /*if (expect_true (o_reify & EV_ANFD_REIFY)) probably a deoptimisation */
+      /*if (ecb_expect_true (o_reify & EV_ANFD_REIFY)) probably a deoptimisation */
         {
           anfd->events = 0;
 
@@ -2142,7 +2463,14 @@ fd_reify (EV_P)
         backend_modify (EV_A_ fd, o_events, anfd->events);
     }
 
-  fdchangecnt = 0;
+  /* normally, fdchangecnt hasn't changed. if it has, then new fds have been added.
+   * this is a rare case (see beginning comment in this function), so we copy them to the
+   * front and hope the backend handles this case.
+   */
+  if (ecb_expect_false (fdchangecnt != changecnt))
+    memmove (fdchanges, fdchanges + changecnt, (fdchangecnt - changecnt) * sizeof (*fdchanges));
+
+  fdchangecnt -= changecnt;
 }
 
 /* something about the given fd changed */
@@ -2151,12 +2479,12 @@ void
 fd_change (EV_P_ int fd, int flags)
 {
   unsigned char reify = anfds [fd].reify;
-  anfds [fd].reify |= flags;
+  anfds [fd].reify = reify | flags;
 
-  if (expect_true (!reify))
+  if (ecb_expect_true (!reify))
     {
       ++fdchangecnt;
-      array_needsize (int, fdchanges, fdchangemax, fdchangecnt, EMPTY2);
+      array_needsize (int, fdchanges, fdchangemax, fdchangecnt, array_needsize_noinit);
       fdchanges [fdchangecnt - 1] = fd;
     }
 }
@@ -2186,7 +2514,7 @@ fd_valid (int fd)
 }
 
 /* called on EBADF to verify fds */
-noinline ecb_cold
+ecb_noinline ecb_cold
 static void
 fd_ebadf (EV_P)
 {
@@ -2199,7 +2527,7 @@ fd_ebadf (EV_P)
 }
 
 /* called on ENOMEM in select/poll to kill some fds and retry */
-noinline ecb_cold
+ecb_noinline ecb_cold
 static void
 fd_enomem (EV_P)
 {
@@ -2214,7 +2542,7 @@ fd_enomem (EV_P)
 }
 
 /* usually called after fork if backend needs to re-arm all fds from scratch */
-noinline
+ecb_noinline
 static void
 fd_rearm_all (EV_P)
 {
@@ -2278,19 +2606,19 @@ downheap (ANHE *heap, int N, int k)
       ANHE *pos = heap + DHEAP * (k - HEAP0) + HEAP0 + 1;
 
       /* find minimum child */
-      if (expect_true (pos + DHEAP - 1 < E))
+      if (ecb_expect_true (pos + DHEAP - 1 < E))
         {
           /* fast path */                               (minpos = pos + 0), (minat = ANHE_at (*minpos));
-          if (               ANHE_at (pos [1]) < minat) (minpos = pos + 1), (minat = ANHE_at (*minpos));
-          if (               ANHE_at (pos [2]) < minat) (minpos = pos + 2), (minat = ANHE_at (*minpos));
-          if (               ANHE_at (pos [3]) < minat) (minpos = pos + 3), (minat = ANHE_at (*minpos));
+          if (               minat > ANHE_at (pos [1])) (minpos = pos + 1), (minat = ANHE_at (*minpos));
+          if (               minat > ANHE_at (pos [2])) (minpos = pos + 2), (minat = ANHE_at (*minpos));
+          if (               minat > ANHE_at (pos [3])) (minpos = pos + 3), (minat = ANHE_at (*minpos));
         }
       else if (pos < E)
         {
           /* slow path */                               (minpos = pos + 0), (minat = ANHE_at (*minpos));
-          if (pos + 1 < E && ANHE_at (pos [1]) < minat) (minpos = pos + 1), (minat = ANHE_at (*minpos));
-          if (pos + 2 < E && ANHE_at (pos [2]) < minat) (minpos = pos + 2), (minat = ANHE_at (*minpos));
-          if (pos + 3 < E && ANHE_at (pos [3]) < minat) (minpos = pos + 3), (minat = ANHE_at (*minpos));
+          if (pos + 1 < E && minat > ANHE_at (pos [1])) (minpos = pos + 1), (minat = ANHE_at (*minpos));
+          if (pos + 2 < E && minat > ANHE_at (pos [2])) (minpos = pos + 2), (minat = ANHE_at (*minpos));
+          if (pos + 3 < E && minat > ANHE_at (pos [3])) (minpos = pos + 3), (minat = ANHE_at (*minpos));
         }
       else
         break;
@@ -2308,7 +2636,7 @@ downheap (ANHE *heap, int N, int k)
   ev_active (ANHE_w (he)) = k;
 }
 
-#else /* 4HEAP */
+#else /* not 4HEAP */
 
 #define HEAP0 1
 #define HPARENT(k) ((k) >> 1)
@@ -2390,7 +2718,7 @@ reheap (ANHE *heap, int N)
 
 /*****************************************************************************/
 
-/* associate signal watchers to a signal signal */
+/* associate signal watchers to a signal */
 typedef struct
 {
   EV_ATOMIC_T pending;
@@ -2406,7 +2734,7 @@ static ANSIG signals [EV_NSIG - 1];
 
 #if EV_SIGNAL_ENABLE || EV_ASYNC_ENABLE
 
-noinline ecb_cold
+ecb_noinline ecb_cold
 static void
 evpipe_init (EV_P)
 {
@@ -2457,7 +2785,7 @@ evpipe_write (EV_P_ EV_ATOMIC_T *flag)
 {
   ECB_MEMORY_FENCE; /* push out the write before this function was called, acquire flag */
 
-  if (expect_true (*flag))
+  if (ecb_expect_true (*flag))
     return;
 
   *flag = 1;
@@ -2544,7 +2872,7 @@ pipecb (EV_P_ ev_io *iow, int revents)
       ECB_MEMORY_FENCE;
 
       for (i = EV_NSIG - 1; i--; )
-        if (expect_false (signals [i].pending))
+        if (ecb_expect_false (signals [i].pending))
           ev_feed_signal_event (EV_A_ i + 1);
     }
 #endif
@@ -2595,13 +2923,13 @@ ev_sighandler (int signum)
   ev_feed_signal (signum);
 }
 
-noinline
+ecb_noinline
 void
 ev_feed_signal_event (EV_P_ int signum) EV_NOEXCEPT
 {
   WL w;
 
-  if (expect_false (signum <= 0 || signum >= EV_NSIG))
+  if (ecb_expect_false (signum <= 0 || signum >= EV_NSIG))
     return;
 
   --signum;
@@ -2610,7 +2938,7 @@ ev_feed_signal_event (EV_P_ int signum) EV_NOEXCEPT
   /* it is permissible to try to feed a signal to the wrong loop */
   /* or, likely more useful, feeding a signal nobody is waiting for */
 
-  if (expect_false (signals [signum].loop != EV_A))
+  if (ecb_expect_false (signals [signum].loop != EV_A))
     return;
 #endif
 
@@ -2704,6 +3032,57 @@ childcb (EV_P_ ev_signal *sw, int revents)
 
 /*****************************************************************************/
 
+#if EV_USE_TIMERFD
+
+static void periodics_reschedule (EV_P);
+
+static void
+timerfdcb (EV_P_ ev_io *iow, int revents)
+{
+  struct itimerspec its = { 0 };
+
+  its.it_value.tv_sec = ev_rt_now + (int)MAX_BLOCKTIME2;
+  timerfd_settime (timerfd, TFD_TIMER_ABSTIME | TFD_TIMER_CANCEL_ON_SET, &its, 0);
+
+  ev_rt_now = ev_time ();
+  /* periodics_reschedule only needs ev_rt_now */
+  /* but maybe in the future we want the full treatment. */
+  /*
+  now_floor = EV_TS_CONST (0.);
+  time_update (EV_A_ EV_TSTAMP_HUGE);
+  */
+#if EV_PERIODIC_ENABLE
+  periodics_reschedule (EV_A);
+#endif
+}
+
+ecb_noinline ecb_cold
+static void
+evtimerfd_init (EV_P)
+{
+  if (!ev_is_active (&timerfd_w))
+    {
+      timerfd = timerfd_create (CLOCK_REALTIME, TFD_NONBLOCK | TFD_CLOEXEC);
+
+      if (timerfd >= 0)
+        {
+          fd_intern (timerfd); /* just to be sure */
+
+          ev_io_init (&timerfd_w, timerfdcb, timerfd, EV_READ);
+          ev_set_priority (&timerfd_w, EV_MINPRI);
+          ev_io_start (EV_A_ &timerfd_w);
+          ev_unref (EV_A); /* watcher should not keep loop alive */
+
+          /* (re-) arm timer */
+          timerfdcb (EV_A_ 0, 0);
+        }
+    }
+}
+
+#endif
+
+/*****************************************************************************/
+
 #if EV_USE_IOCP
 # include "ev_iocp.c"
 #endif
@@ -2716,6 +3095,12 @@ childcb (EV_P_ ev_signal *sw, int revents)
 #if EV_USE_EPOLL
 # include "ev_epoll.c"
 #endif
+#if EV_USE_LINUXAIO
+# include "ev_linuxaio.c"
+#endif
+#if EV_USE_IOURING
+# include "ev_iouring.c"
+#endif
 #if EV_USE_POLL
 # include "ev_poll.c"
 #endif
@@ -2753,11 +3138,13 @@ ev_supported_backends (void) EV_NOEXCEPT
 {
   unsigned int flags = 0;
 
-  if (EV_USE_PORT  ) flags |= EVBACKEND_PORT;
-  if (EV_USE_KQUEUE) flags |= EVBACKEND_KQUEUE;
-  if (EV_USE_EPOLL ) flags |= EVBACKEND_EPOLL;
-  if (EV_USE_POLL  ) flags |= EVBACKEND_POLL;
-  if (EV_USE_SELECT) flags |= EVBACKEND_SELECT;
+  if (EV_USE_PORT                                      ) flags |= EVBACKEND_PORT;
+  if (EV_USE_KQUEUE                                    ) flags |= EVBACKEND_KQUEUE;
+  if (EV_USE_EPOLL                                     ) flags |= EVBACKEND_EPOLL;
+  if (EV_USE_LINUXAIO                                  ) flags |= EVBACKEND_LINUXAIO;
+  if (EV_USE_IOURING && ev_linux_version () >= 0x050601) flags |= EVBACKEND_IOURING; /* 5.6.1+ */
+  if (EV_USE_POLL                                      ) flags |= EVBACKEND_POLL;
+  if (EV_USE_SELECT                                    ) flags |= EVBACKEND_SELECT;
 
   return flags;
 }
@@ -2782,6 +3169,15 @@ ev_recommended_backends (void) EV_NOEXCEPT
   flags &= ~EVBACKEND_POLL;   /* poll return value is unusable (http://forums.freebsd.org/archive/index.php/t-10270.html) */
 #endif
 
+  /* TODO: linuxaio is very experimental */
+#if !EV_RECOMMEND_LINUXAIO
+  flags &= ~EVBACKEND_LINUXAIO;
+#endif
+  /* TODO: linuxaio is super experimental */
+#if !EV_RECOMMEND_IOURING
+  flags &= ~EVBACKEND_IOURING;
+#endif
+
   return flags;
 }
 
@@ -2789,12 +3185,14 @@ ecb_cold
 unsigned int
 ev_embeddable_backends (void) EV_NOEXCEPT
 {
-  int flags = EVBACKEND_EPOLL | EVBACKEND_KQUEUE | EVBACKEND_PORT;
+  int flags = EVBACKEND_EPOLL | EVBACKEND_KQUEUE | EVBACKEND_PORT | EVBACKEND_IOURING;
 
   /* epoll embeddability broken on all linux versions up to at least 2.6.23 */
   if (ev_linux_version () < 0x020620) /* disable it on linux < 2.6.32 */
     flags &= ~EVBACKEND_EPOLL;
 
+  /* EVBACKEND_LINUXAIO is theoretically embeddable, but suffers from a performance overhead */
+
   return flags;
 }
 
@@ -2855,20 +3253,8 @@ ev_set_loop_release_cb (EV_P_ void (*release)(EV_P) EV_NOEXCEPT, void (*acquire)
 }
 #endif
 
-EV_INLINE struct ev_loop *
-ev_default_loop_uc_ (void) EV_NOEXCEPT
-{
-	return ev_default_loop_ptr;
-}
-
-EV_INLINE int
-ev_is_default_loop (EV_P) EV_NOEXCEPT
-{
-	return EV_A == EV_DEFAULT_UC;
-}
-
 /* initialise a loop structure, must be zero-initialised */
-noinline ecb_cold
+ecb_noinline ecb_cold
 static void
 loop_init (EV_P_ unsigned int flags) EV_NOEXCEPT
 {
@@ -2952,27 +3338,36 @@ loop_init (EV_P_ unsigned int flags) EV_NOEXCEPT
 #if EV_USE_SIGNALFD
       sigfd              = flags & EVFLAG_SIGNALFD  ? -2 : -1;
 #endif
+#if EV_USE_TIMERFD
+      timerfd            = flags & EVFLAG_NOTIMERFD ? -1 : -2;
+#endif
 
       if (!(flags & EVBACKEND_MASK))
         flags |= ev_recommended_backends ();
 
 #if EV_USE_IOCP
-      if (!backend && (flags & EVBACKEND_IOCP  )) backend = iocp_init   (EV_A_ flags);
+      if (!backend && (flags & EVBACKEND_IOCP    )) backend = iocp_init      (EV_A_ flags);
 #endif
 #if EV_USE_PORT
-      if (!backend && (flags & EVBACKEND_PORT  )) backend = port_init   (EV_A_ flags);
+      if (!backend && (flags & EVBACKEND_PORT    )) backend = port_init      (EV_A_ flags);
 #endif
 #if EV_USE_KQUEUE
-      if (!backend && (flags & EVBACKEND_KQUEUE)) backend = kqueue_init (EV_A_ flags);
+      if (!backend && (flags & EVBACKEND_KQUEUE  )) backend = kqueue_init    (EV_A_ flags);
+#endif
+#if EV_USE_IOURING
+      if (!backend && (flags & EVBACKEND_IOURING )) backend = iouring_init   (EV_A_ flags);
+#endif
+#if EV_USE_LINUXAIO
+      if (!backend && (flags & EVBACKEND_LINUXAIO)) backend = linuxaio_init  (EV_A_ flags);
 #endif
 #if EV_USE_EPOLL
-      if (!backend && (flags & EVBACKEND_EPOLL )) backend = epoll_init  (EV_A_ flags);
+      if (!backend && (flags & EVBACKEND_EPOLL   )) backend = epoll_init     (EV_A_ flags);
 #endif
 #if EV_USE_POLL
-      if (!backend && (flags & EVBACKEND_POLL  )) backend = poll_init   (EV_A_ flags);
+      if (!backend && (flags & EVBACKEND_POLL    )) backend = poll_init      (EV_A_ flags);
 #endif
 #if EV_USE_SELECT
-      if (!backend && (flags & EVBACKEND_SELECT)) backend = select_init (EV_A_ flags);
+      if (!backend && (flags & EVBACKEND_SELECT  )) backend = select_init    (EV_A_ flags);
 #endif
 
       ev_prepare_init (&pending_w, pendingcb);
@@ -2984,6 +3379,18 @@ loop_init (EV_P_ unsigned int flags) EV_NOEXCEPT
     }
 }
 
+EV_INLINE struct ev_loop *
+ev_default_loop_uc_ (void) EV_NOEXCEPT
+{
+	return ev_default_loop_ptr;
+}
+
+EV_INLINE int
+ev_is_default_loop (EV_P) EV_NOEXCEPT
+{
+	return EV_A == EV_DEFAULT_UC;
+}
+
 /* free up a loop structure */
 ecb_cold
 void
@@ -2999,7 +3406,7 @@ ev_loop_destroy (EV_P)
 
 #if EV_CLEANUP_ENABLE
   /* queue cleanup watchers (and execute them) */
-  if (expect_false (cleanupcnt))
+  if (ecb_expect_false (cleanupcnt))
     {
       queue_events (EV_A_ (W *)cleanups, cleanupcnt, EV_CLEANUP);
       EV_INVOKE_PENDING;
@@ -3028,6 +3435,11 @@ ev_loop_destroy (EV_P)
     close (sigfd);
 #endif
 
+#if EV_USE_TIMERFD
+  if (ev_is_active (&timerfd_w))
+    close (timerfd);
+#endif
+
 #if EV_USE_INOTIFY
   if (fs_fd >= 0)
     close (fs_fd);
@@ -3037,22 +3449,28 @@ ev_loop_destroy (EV_P)
     close (backend_fd);
 
 #if EV_USE_IOCP
-  if (backend == EVBACKEND_IOCP  ) iocp_destroy   (EV_A);
+  if (backend == EVBACKEND_IOCP    ) iocp_destroy     (EV_A);
 #endif
 #if EV_USE_PORT
-  if (backend == EVBACKEND_PORT  ) port_destroy   (EV_A);
+  if (backend == EVBACKEND_PORT    ) port_destroy     (EV_A);
 #endif
 #if EV_USE_KQUEUE
-  if (backend == EVBACKEND_KQUEUE) kqueue_destroy (EV_A);
+  if (backend == EVBACKEND_KQUEUE  ) kqueue_destroy   (EV_A);
+#endif
+#if EV_USE_IOURING
+  if (backend == EVBACKEND_IOURING ) iouring_destroy  (EV_A);
+#endif
+#if EV_USE_LINUXAIO
+  if (backend == EVBACKEND_LINUXAIO) linuxaio_destroy (EV_A);
 #endif
 #if EV_USE_EPOLL
-  if (backend == EVBACKEND_EPOLL ) epoll_destroy  (EV_A);
+  if (backend == EVBACKEND_EPOLL   ) epoll_destroy    (EV_A);
 #endif
 #if EV_USE_POLL
-  if (backend == EVBACKEND_POLL  ) poll_destroy   (EV_A);
+  if (backend == EVBACKEND_POLL    ) poll_destroy     (EV_A);
 #endif
 #if EV_USE_SELECT
-  if (backend == EVBACKEND_SELECT) select_destroy (EV_A);
+  if (backend == EVBACKEND_SELECT  ) select_destroy   (EV_A);
 #endif
 
   for (i = NUMPRI; i--; )
@@ -3104,34 +3522,62 @@ inline_size void
 loop_fork (EV_P)
 {
 #if EV_USE_PORT
-  if (backend == EVBACKEND_PORT  ) port_fork   (EV_A);
+  if (backend == EVBACKEND_PORT    ) port_fork     (EV_A);
 #endif
 #if EV_USE_KQUEUE
-  if (backend == EVBACKEND_KQUEUE) kqueue_fork (EV_A);
+  if (backend == EVBACKEND_KQUEUE  ) kqueue_fork   (EV_A);
+#endif
+#if EV_USE_IOURING
+  if (backend == EVBACKEND_IOURING ) iouring_fork  (EV_A);
+#endif
+#if EV_USE_LINUXAIO
+  if (backend == EVBACKEND_LINUXAIO) linuxaio_fork (EV_A);
 #endif
 #if EV_USE_EPOLL
-  if (backend == EVBACKEND_EPOLL ) epoll_fork  (EV_A);
+  if (backend == EVBACKEND_EPOLL   ) epoll_fork    (EV_A);
 #endif
 #if EV_USE_INOTIFY
   infy_fork (EV_A);
 #endif
 
-#if EV_SIGNAL_ENABLE || EV_ASYNC_ENABLE
-  if (ev_is_active (&pipe_w) && postfork != 2)
+  if (postfork != 2)
     {
-      /* pipe_write_wanted must be false now, so modifying fd vars should be safe */
+      #if EV_USE_SIGNALFD
+        /* surprisingly, nothing needs to be done for signalfd, accoridng to docs, it does the right thing on fork */
+      #endif
 
-      ev_ref (EV_A);
-      ev_io_stop (EV_A_ &pipe_w);
+      #if EV_USE_TIMERFD
+        if (ev_is_active (&timerfd_w))
+          {
+            ev_ref (EV_A);
+            ev_io_stop (EV_A_ &timerfd_w);
+
+            close (timerfd);
+            timerfd = -2;
 
-      if (evpipe [0] >= 0)
-        EV_WIN32_CLOSE_FD (evpipe [0]);
+            evtimerfd_init (EV_A);
+            /* reschedule periodics, in case we missed something */
+            ev_feed_event (EV_A_ &timerfd_w, EV_CUSTOM);
+          }
+      #endif
+
+      #if EV_SIGNAL_ENABLE || EV_ASYNC_ENABLE
+        if (ev_is_active (&pipe_w))
+          {
+            /* pipe_write_wanted must be false now, so modifying fd vars should be safe */
 
-      evpipe_init (EV_A);
-      /* iterate over everything, in case we missed something before */
-      ev_feed_event (EV_A_ &pipe_w, EV_CUSTOM);
+            ev_ref (EV_A);
+            ev_io_stop (EV_A_ &pipe_w);
+
+            if (evpipe [0] >= 0)
+              EV_WIN32_CLOSE_FD (evpipe [0]);
+
+            evpipe_init (EV_A);
+            /* iterate over everything, in case we missed something before */
+            ev_feed_event (EV_A_ &pipe_w, EV_CUSTOM);
+          }
+      #endif
     }
-#endif
 
   postfork = 0;
 }
@@ -3157,7 +3603,7 @@ ev_loop_new (unsigned int flags) EV_NOEXCEPT
 #endif /* multiplicity */
 
 #if EV_VERIFY
-noinline ecb_cold
+ecb_noinline ecb_cold
 static void
 verify_watcher (EV_P_ W w)
 {
@@ -3167,7 +3613,7 @@ verify_watcher (EV_P_ W w)
     assert (("libev: pending watcher not on pending queue", pendings [ABSPRI (w)][w->pending - 1].w == w));
 }
 
-noinline ecb_cold
+ecb_noinline ecb_cold
 static void
 verify_heap (EV_P_ ANHE *heap, int N)
 {
@@ -3183,7 +3629,7 @@ verify_heap (EV_P_ ANHE *heap, int N)
     }
 }
 
-noinline ecb_cold
+ecb_noinline ecb_cold
 static void
 array_verify (EV_P_ W *ws, int cnt)
 {
@@ -3342,7 +3788,7 @@ ev_pending_count (EV_P) EV_NOEXCEPT
   return count;
 }
 
-noinline
+ecb_noinline
 void
 ev_invoke_pending (EV_P)
 {
@@ -3371,7 +3817,7 @@ ev_invoke_pending (EV_P)
 inline_size void
 idle_reify (EV_P)
 {
-  if (expect_false (idleall))
+  if (ecb_expect_false (idleall))
     {
       int pri;
 
@@ -3411,7 +3857,7 @@ timers_reify (EV_P)
               if (ev_at (w) < mn_now)
                 ev_at (w) = mn_now;
 
-              assert (("libev: negative ev_timer repeat value found while processing timers", w->repeat > 0.));
+              assert (("libev: negative ev_timer repeat value found while processing timers", w->repeat > EV_TS_CONST (0.)));
 
               ANHE_at_cache (timers [HEAP0]);
               downheap (timers, timercnt, HEAP0);
@@ -3430,7 +3876,7 @@ timers_reify (EV_P)
 
 #if EV_PERIODIC_ENABLE
 
-noinline
+ecb_noinline
 static void
 periodic_recalc (EV_P_ ev_periodic *w)
 {
@@ -3443,7 +3889,7 @@ periodic_recalc (EV_P_ ev_periodic *w)
       ev_tstamp nat = at + w->interval;
 
       /* when resolution fails us, we use ev_rt_now */
-      if (expect_false (nat == at))
+      if (ecb_expect_false (nat == at))
         {
           at = ev_rt_now;
           break;
@@ -3499,7 +3945,7 @@ periodics_reify (EV_P)
 
 /* simply recalculate all periodics */
 /* TODO: maybe ensure that at least one event happens when jumping forward? */
-noinline ecb_cold
+ecb_noinline ecb_cold
 static void
 periodics_reschedule (EV_P)
 {
@@ -3523,7 +3969,7 @@ periodics_reschedule (EV_P)
 #endif
 
 /* adjust all timers by a given offset */
-noinline ecb_cold
+ecb_noinline ecb_cold
 static void
 timers_reschedule (EV_P_ ev_tstamp adjust)
 {
@@ -3543,7 +3989,7 @@ inline_speed void
 time_update (EV_P_ ev_tstamp max_block)
 {
 #if EV_USE_MONOTONIC
-  if (expect_true (have_monotonic))
+  if (ecb_expect_true (have_monotonic))
     {
       int i;
       ev_tstamp odiff = rtmn_diff;
@@ -3552,7 +3998,7 @@ time_update (EV_P_ ev_tstamp max_block)
 
       /* only fetch the realtime clock every 0.5*MIN_TIMEJUMP seconds */
       /* interpolate in the meantime */
-      if (expect_true (mn_now - now_floor < MIN_TIMEJUMP * .5))
+      if (ecb_expect_true (mn_now - now_floor < EV_TS_CONST (MIN_TIMEJUMP * .5)))
         {
           ev_rt_now = rtmn_diff + mn_now;
           return;
@@ -3576,7 +4022,7 @@ time_update (EV_P_ ev_tstamp max_block)
 
           diff = odiff - rtmn_diff;
 
-          if (expect_true ((diff < 0. ? -diff : diff) < MIN_TIMEJUMP))
+          if (ecb_expect_true ((diff < EV_TS_CONST (0.) ? -diff : diff) < EV_TS_CONST (MIN_TIMEJUMP)))
             return; /* all is well */
 
           ev_rt_now = ev_time ();
@@ -3595,7 +4041,7 @@ time_update (EV_P_ ev_tstamp max_block)
     {
       ev_rt_now = ev_time ();
 
-      if (expect_false (mn_now > ev_rt_now || ev_rt_now > mn_now + max_block + MIN_TIMEJUMP))
+      if (ecb_expect_false (mn_now > ev_rt_now || ev_rt_now > mn_now + max_block + EV_TS_CONST (MIN_TIMEJUMP)))
         {
           /* adjust timers. this is easy, as the offset is the same for all of them */
           timers_reschedule (EV_A_ ev_rt_now - mn_now);
@@ -3628,8 +4074,8 @@ ev_run (EV_P_ int flags)
 #endif
 
 #ifndef _WIN32
-      if (expect_false (curpid)) /* penalise the forking check even more */
-        if (expect_false (getpid () != curpid))
+      if (ecb_expect_false (curpid)) /* penalise the forking check even more */
+        if (ecb_expect_false (getpid () != curpid))
           {
             curpid = getpid ();
             postfork = 1;
@@ -3638,7 +4084,7 @@ ev_run (EV_P_ int flags)
 
 #if EV_FORK_ENABLE
       /* we might have forked, so queue fork handlers */
-      if (expect_false (postfork))
+      if (ecb_expect_false (postfork))
         if (forkcnt)
           {
             queue_events (EV_A_ (W *)forks, forkcnt, EV_FORK);
@@ -3648,18 +4094,18 @@ ev_run (EV_P_ int flags)
 
 #if EV_PREPARE_ENABLE
       /* queue prepare watchers (and execute them) */
-      if (expect_false (preparecnt))
+      if (ecb_expect_false (preparecnt))
         {
           queue_events (EV_A_ (W *)prepares, preparecnt, EV_PREPARE);
           EV_INVOKE_PENDING;
         }
 #endif
 
-      if (expect_false (loop_done))
+      if (ecb_expect_false (loop_done))
         break;
 
       /* we might have forked, so reify kernel state if necessary */
-      if (expect_false (postfork))
+      if (ecb_expect_false (postfork))
         loop_fork (EV_A);
 
       /* update fd-related kernel structures */
@@ -3674,16 +4120,28 @@ ev_run (EV_P_ int flags)
         ev_tstamp prev_mn_now = mn_now;
 
         /* update time to cancel out callback processing overhead */
-        time_update (EV_A_ 1e100);
+        time_update (EV_A_ EV_TS_CONST (EV_TSTAMP_HUGE));
 
         /* from now on, we want a pipe-wake-up */
         pipe_write_wanted = 1;
 
         ECB_MEMORY_FENCE; /* make sure pipe_write_wanted is visible before we check for potential skips */
 
-        if (expect_true (!(flags & EVRUN_NOWAIT || idleall || !activecnt || pipe_write_skipped)))
+        if (ecb_expect_true (!(flags & EVRUN_NOWAIT || idleall || !activecnt || pipe_write_skipped)))
           {
-            waittime = MAX_BLOCKTIME;
+            waittime = EV_TS_CONST (MAX_BLOCKTIME);
+
+#if EV_USE_TIMERFD
+            /* sleep a lot longer when we can reliably detect timejumps */
+            if (ecb_expect_true (timerfd >= 0))
+              waittime = EV_TS_CONST (MAX_BLOCKTIME2);
+#endif
+#if !EV_PERIODIC_ENABLE
+            /* without periodics but with monotonic clock there is no need */
+            /* for any time jump detection, so sleep longer */
+            if (ecb_expect_true (have_monotonic))
+              waittime = EV_TS_CONST (MAX_BLOCKTIME2);
+#endif
 
             if (timercnt)
               {
@@ -3700,23 +4158,28 @@ ev_run (EV_P_ int flags)
 #endif
 
             /* don't let timeouts decrease the waittime below timeout_blocktime */
-            if (expect_false (waittime < timeout_blocktime))
+            if (ecb_expect_false (waittime < timeout_blocktime))
               waittime = timeout_blocktime;
 
-            /* at this point, we NEED to wait, so we have to ensure */
-            /* to pass a minimum nonzero value to the backend */
-            if (expect_false (waittime < backend_mintime))
-              waittime = backend_mintime;
+            /* now there are two more special cases left, either we have
+             * already-expired timers, so we should not sleep, or we have timers
+             * that expire very soon, in which case we need to wait for a minimum
+             * amount of time for some event loop backends.
+             */
+            if (ecb_expect_false (waittime < backend_mintime))
+              waittime = waittime <= EV_TS_CONST (0.)
+                 ? EV_TS_CONST (0.)
+                 : backend_mintime;
 
             /* extra check because io_blocktime is commonly 0 */
-            if (expect_false (io_blocktime))
+            if (ecb_expect_false (io_blocktime))
               {
                 sleeptime = io_blocktime - (mn_now - prev_mn_now);
 
                 if (sleeptime > waittime - backend_mintime)
                   sleeptime = waittime - backend_mintime;
 
-                if (expect_true (sleeptime > 0.))
+                if (ecb_expect_true (sleeptime > EV_TS_CONST (0.)))
                   {
                     ev_sleep (sleeptime);
                     waittime -= sleeptime;
@@ -3740,7 +4203,6 @@ ev_run (EV_P_ int flags)
             ev_feed_event (EV_A_ &pipe_w, EV_CUSTOM);
           }
 
-
         /* update ev_rt_now, do magic */
         time_update (EV_A_ waittime + sleeptime);
       }
@@ -3758,13 +4220,13 @@ ev_run (EV_P_ int flags)
 
 #if EV_CHECK_ENABLE
       /* queue check watchers, to be executed first */
-      if (expect_false (checkcnt))
+      if (ecb_expect_false (checkcnt))
         queue_events (EV_A_ (W *)checks, checkcnt, EV_CHECK);
 #endif
 
       EV_INVOKE_PENDING;
     }
-  while (expect_true (
+  while (ecb_expect_true (
     activecnt
     && !loop_done
     && !(flags & (EVRUN_ONCE | EVRUN_NOWAIT))
@@ -3798,22 +4260,10 @@ ev_unref (EV_P) EV_NOEXCEPT
   --activecnt;
 }
 
-int
-ev_active_cnt (EV_P) EV_NOEXCEPT
-{
-	return activecnt;
-}
-
 void
 ev_now_update (EV_P) EV_NOEXCEPT
 {
-  time_update (EV_A_ 1e100);
-}
-
-void
-ev_now_update_if_cheap (EV_P) EV_NOEXCEPT
-{
-  if (have_cheap_timer) time_update (EV_A_ 1e100);
+  time_update (EV_A_ EV_TSTAMP_HUGE);
 }
 
 void
@@ -3850,7 +4300,7 @@ wlist_del (WL *head, WL elem)
 {
   while (*head)
     {
-      if (expect_true (*head == elem))
+      if (ecb_expect_true (*head == elem))
         {
           *head = elem->next;
           break;
@@ -3877,7 +4327,7 @@ ev_clear_pending (EV_P_ void *w) EV_NOEXCEPT
   W w_ = (W)w;
   int pending = w_->pending;
 
-  if (expect_true (pending))
+  if (ecb_expect_true (pending))
     {
       ANPENDING *p = pendings [ABSPRI (w_)] + pending - 1;
       p->w = (W)&pending_w;
@@ -3914,43 +4364,49 @@ ev_stop (EV_P_ W w)
 
 /*****************************************************************************/
 
-noinline
+ecb_noinline
 void
 ev_io_start (EV_P_ ev_io *w) EV_NOEXCEPT
 {
   int fd = w->fd;
 
-  if (expect_false (ev_is_active (w)))
+  if (ecb_expect_false (ev_is_active (w)))
     return;
 
   assert (("libev: ev_io_start called with negative fd", fd >= 0));
   assert (("libev: ev_io_start called with illegal event mask", !(w->events & ~(EV__IOFDSET | EV_READ | EV_WRITE))));
 
+#if EV_VERIFY >= 2
+  assert (("libev: ev_io_start called on watcher with invalid fd", fd_valid (fd)));
+#endif
   EV_FREQUENT_CHECK;
 
   ev_start (EV_A_ (W)w, 1);
-  array_needsize (ANFD, anfds, anfdmax, fd + 1, array_init_zero);
+  array_needsize (ANFD, anfds, anfdmax, fd + 1, array_needsize_zerofill);
   wlist_add (&anfds[fd].head, (WL)w);
 
   /* common bug, apparently */
   assert (("libev: ev_io_start called with corrupted watcher", ((WL)w)->next != (WL)w));
 
-  fd_change (EV_A_ fd, w->events & (EV__IOFDSET | EV_ANFD_REIFY));
+  fd_change (EV_A_ fd, w->events & EV__IOFDSET | EV_ANFD_REIFY);
   w->events &= ~EV__IOFDSET;
 
   EV_FREQUENT_CHECK;
 }
 
-noinline
+ecb_noinline
 void
 ev_io_stop (EV_P_ ev_io *w) EV_NOEXCEPT
 {
   clear_pending (EV_A_ (W)w);
-  if (expect_false (!ev_is_active (w)))
+  if (ecb_expect_false (!ev_is_active (w)))
     return;
 
   assert (("libev: ev_io_stop called with illegal fd (must stay constant after start!)", w->fd >= 0 && w->fd < anfdmax));
 
+#if EV_VERIFY >= 2
+  assert (("libev: ev_io_stop called on watcher with invalid fd", fd_valid (w->fd)));
+#endif
   EV_FREQUENT_CHECK;
 
   wlist_del (&anfds[w->fd].head, (WL)w);
@@ -3961,11 +4417,11 @@ ev_io_stop (EV_P_ ev_io *w) EV_NOEXCEPT
   EV_FREQUENT_CHECK;
 }
 
-noinline
+ecb_noinline
 void
 ev_timer_start (EV_P_ ev_timer *w) EV_NOEXCEPT
 {
-  if (expect_false (ev_is_active (w)))
+  if (ecb_expect_false (ev_is_active (w)))
     return;
 
   ev_at (w) += mn_now;
@@ -3976,7 +4432,7 @@ ev_timer_start (EV_P_ ev_timer *w) EV_NOEXCEPT
 
   ++timercnt;
   ev_start (EV_A_ (W)w, timercnt + HEAP0 - 1);
-  array_needsize (ANHE, timers, timermax, ev_active (w) + 1, EMPTY2);
+  array_needsize (ANHE, timers, timermax, ev_active (w) + 1, array_needsize_noinit);
   ANHE_w (timers [ev_active (w)]) = (WT)w;
   ANHE_at_cache (timers [ev_active (w)]);
   upheap (timers, ev_active (w));
@@ -3986,12 +4442,12 @@ ev_timer_start (EV_P_ ev_timer *w) EV_NOEXCEPT
   /*assert (("libev: internal timer heap corruption", timers [ev_active (w)] == (WT)w));*/
 }
 
-noinline
+ecb_noinline
 void
 ev_timer_stop (EV_P_ ev_timer *w) EV_NOEXCEPT
 {
   clear_pending (EV_A_ (W)w);
-  if (expect_false (!ev_is_active (w)))
+  if (ecb_expect_false (!ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
@@ -4003,7 +4459,7 @@ ev_timer_stop (EV_P_ ev_timer *w) EV_NOEXCEPT
 
     --timercnt;
 
-    if (expect_true (active < timercnt + HEAP0))
+    if (ecb_expect_true (active < timercnt + HEAP0))
       {
         timers [active] = timers [timercnt + HEAP0];
         adjustheap (timers, timercnt, active);
@@ -4017,7 +4473,7 @@ ev_timer_stop (EV_P_ ev_timer *w) EV_NOEXCEPT
   EV_FREQUENT_CHECK;
 }
 
-noinline
+ecb_noinline
 void
 ev_timer_again (EV_P_ ev_timer *w) EV_NOEXCEPT
 {
@@ -4048,17 +4504,22 @@ ev_timer_again (EV_P_ ev_timer *w) EV_NOEXCEPT
 ev_tstamp
 ev_timer_remaining (EV_P_ ev_timer *w) EV_NOEXCEPT
 {
-  return ev_at (w) - (ev_is_active (w) ? mn_now : 0.);
+  return ev_at (w) - (ev_is_active (w) ? mn_now : EV_TS_CONST (0.));
 }
 
 #if EV_PERIODIC_ENABLE
-noinline
+ecb_noinline
 void
 ev_periodic_start (EV_P_ ev_periodic *w) EV_NOEXCEPT
 {
-  if (expect_false (ev_is_active (w)))
+  if (ecb_expect_false (ev_is_active (w)))
     return;
 
+#if EV_USE_TIMERFD
+  if (timerfd == -2)
+    evtimerfd_init (EV_A);
+#endif
+
   if (w->reschedule_cb)
     ev_at (w) = w->reschedule_cb (w, ev_rt_now);
   else if (w->interval)
@@ -4073,7 +4534,7 @@ ev_periodic_start (EV_P_ ev_periodic *w) EV_NOEXCEPT
 
   ++periodiccnt;
   ev_start (EV_A_ (W)w, periodiccnt + HEAP0 - 1);
-  array_needsize (ANHE, periodics, periodicmax, ev_active (w) + 1, EMPTY2);
+  array_needsize (ANHE, periodics, periodicmax, ev_active (w) + 1, array_needsize_noinit);
   ANHE_w (periodics [ev_active (w)]) = (WT)w;
   ANHE_at_cache (periodics [ev_active (w)]);
   upheap (periodics, ev_active (w));
@@ -4083,12 +4544,12 @@ ev_periodic_start (EV_P_ ev_periodic *w) EV_NOEXCEPT
   /*assert (("libev: internal periodic heap corruption", ANHE_w (periodics [ev_active (w)]) == (WT)w));*/
 }
 
-noinline
+ecb_noinline
 void
 ev_periodic_stop (EV_P_ ev_periodic *w) EV_NOEXCEPT
 {
   clear_pending (EV_A_ (W)w);
-  if (expect_false (!ev_is_active (w)))
+  if (ecb_expect_false (!ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
@@ -4100,7 +4561,7 @@ ev_periodic_stop (EV_P_ ev_periodic *w) EV_NOEXCEPT
 
     --periodiccnt;
 
-    if (expect_true (active < periodiccnt + HEAP0))
+    if (ecb_expect_true (active < periodiccnt + HEAP0))
       {
         periodics [active] = periodics [periodiccnt + HEAP0];
         adjustheap (periodics, periodiccnt, active);
@@ -4112,7 +4573,7 @@ ev_periodic_stop (EV_P_ ev_periodic *w) EV_NOEXCEPT
   EV_FREQUENT_CHECK;
 }
 
-noinline
+ecb_noinline
 void
 ev_periodic_again (EV_P_ ev_periodic *w) EV_NOEXCEPT
 {
@@ -4128,11 +4589,11 @@ ev_periodic_again (EV_P_ ev_periodic *w) EV_NOEXCEPT
 
 #if EV_SIGNAL_ENABLE
 
-noinline
+ecb_noinline
 void
 ev_signal_start (EV_P_ ev_signal *w) EV_NOEXCEPT
 {
-  if (expect_false (ev_is_active (w)))
+  if (ecb_expect_false (ev_is_active (w)))
     return;
 
   assert (("libev: ev_signal_start called with illegal signal number", w->signum > 0 && w->signum < EV_NSIG));
@@ -4211,12 +4672,12 @@ ev_signal_start (EV_P_ ev_signal *w) EV_NOEXCEPT
   EV_FREQUENT_CHECK;
 }
 
-noinline
+ecb_noinline
 void
 ev_signal_stop (EV_P_ ev_signal *w) EV_NOEXCEPT
 {
   clear_pending (EV_A_ (W)w);
-  if (expect_false (!ev_is_active (w)))
+  if (ecb_expect_false (!ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
@@ -4259,7 +4720,7 @@ ev_child_start (EV_P_ ev_child *w) EV_NOEXCEPT
 #if EV_MULTIPLICITY
   assert (("libev: child watchers are only supported in the default loop", loop == ev_default_loop_ptr));
 #endif
-  if (expect_false (ev_is_active (w)))
+  if (ecb_expect_false (ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
@@ -4274,7 +4735,7 @@ void
 ev_child_stop (EV_P_ ev_child *w) EV_NOEXCEPT
 {
   clear_pending (EV_A_ (W)w);
-  if (expect_false (!ev_is_active (w)))
+  if (ecb_expect_false (!ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
@@ -4298,14 +4759,14 @@ ev_child_stop (EV_P_ ev_child *w) EV_NOEXCEPT
 #define NFS_STAT_INTERVAL 30.1074891 /* for filesystems potentially failing inotify */
 #define MIN_STAT_INTERVAL  0.1074891
 
-noinline static void stat_timer_cb (EV_P_ ev_timer *w_, int revents);
+ecb_noinline static void stat_timer_cb (EV_P_ ev_timer *w_, int revents);
 
 #if EV_USE_INOTIFY
 
 /* the * 2 is to allow for alignment padding, which for some reason is >> 8 */
 # define EV_INOTIFY_BUFSIZE (sizeof (struct inotify_event) * 2 + NAME_MAX)
 
-noinline
+ecb_noinline
 static void
 infy_add (EV_P_ ev_stat *w)
 {
@@ -4380,7 +4841,7 @@ infy_add (EV_P_ ev_stat *w)
   if (ev_is_active (&w->timer)) ev_unref (EV_A);
 }
 
-noinline
+ecb_noinline
 static void
 infy_del (EV_P_ ev_stat *w)
 {
@@ -4398,7 +4859,7 @@ infy_del (EV_P_ ev_stat *w)
   inotify_rm_watch (fs_fd, wd);
 }
 
-noinline
+ecb_noinline
 static void
 infy_wd (EV_P_ int slot, int wd, struct inotify_event *ev)
 {
@@ -4554,7 +5015,7 @@ ev_stat_stat (EV_P_ ev_stat *w) EV_NOEXCEPT
     w->attr.st_nlink = 1;
 }
 
-noinline
+ecb_noinline
 static void
 stat_timer_cb (EV_P_ ev_timer *w_, int revents)
 {
@@ -4598,7 +5059,7 @@ stat_timer_cb (EV_P_ ev_timer *w_, int revents)
 void
 ev_stat_start (EV_P_ ev_stat *w) EV_NOEXCEPT
 {
-  if (expect_false (ev_is_active (w)))
+  if (ecb_expect_false (ev_is_active (w)))
     return;
 
   ev_stat_stat (EV_A_ w);
@@ -4630,7 +5091,7 @@ void
 ev_stat_stop (EV_P_ ev_stat *w) EV_NOEXCEPT
 {
   clear_pending (EV_A_ (W)w);
-  if (expect_false (!ev_is_active (w)))
+  if (ecb_expect_false (!ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
@@ -4655,7 +5116,7 @@ ev_stat_stop (EV_P_ ev_stat *w) EV_NOEXCEPT
 void
 ev_idle_start (EV_P_ ev_idle *w) EV_NOEXCEPT
 {
-  if (expect_false (ev_is_active (w)))
+  if (ecb_expect_false (ev_is_active (w)))
     return;
 
   pri_adjust (EV_A_ (W)w);
@@ -4668,7 +5129,7 @@ ev_idle_start (EV_P_ ev_idle *w) EV_NOEXCEPT
     ++idleall;
     ev_start (EV_A_ (W)w, active);
 
-    array_needsize (ev_idle *, idles [ABSPRI (w)], idlemax [ABSPRI (w)], active, EMPTY2);
+    array_needsize (ev_idle *, idles [ABSPRI (w)], idlemax [ABSPRI (w)], active, array_needsize_noinit);
     idles [ABSPRI (w)][active - 1] = w;
   }
 
@@ -4679,7 +5140,7 @@ void
 ev_idle_stop (EV_P_ ev_idle *w) EV_NOEXCEPT
 {
   clear_pending (EV_A_ (W)w);
-  if (expect_false (!ev_is_active (w)))
+  if (ecb_expect_false (!ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
@@ -4702,13 +5163,13 @@ ev_idle_stop (EV_P_ ev_idle *w) EV_NOEXCEPT
 void
 ev_prepare_start (EV_P_ ev_prepare *w) EV_NOEXCEPT
 {
-  if (expect_false (ev_is_active (w)))
+  if (ecb_expect_false (ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
 
   ev_start (EV_A_ (W)w, ++preparecnt);
-  array_needsize (ev_prepare *, prepares, preparemax, preparecnt, EMPTY2);
+  array_needsize (ev_prepare *, prepares, preparemax, preparecnt, array_needsize_noinit);
   prepares [preparecnt - 1] = w;
 
   EV_FREQUENT_CHECK;
@@ -4718,7 +5179,7 @@ void
 ev_prepare_stop (EV_P_ ev_prepare *w) EV_NOEXCEPT
 {
   clear_pending (EV_A_ (W)w);
-  if (expect_false (!ev_is_active (w)))
+  if (ecb_expect_false (!ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
@@ -4740,13 +5201,13 @@ ev_prepare_stop (EV_P_ ev_prepare *w) EV_NOEXCEPT
 void
 ev_check_start (EV_P_ ev_check *w) EV_NOEXCEPT
 {
-  if (expect_false (ev_is_active (w)))
+  if (ecb_expect_false (ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
 
   ev_start (EV_A_ (W)w, ++checkcnt);
-  array_needsize (ev_check *, checks, checkmax, checkcnt, EMPTY2);
+  array_needsize (ev_check *, checks, checkmax, checkcnt, array_needsize_noinit);
   checks [checkcnt - 1] = w;
 
   EV_FREQUENT_CHECK;
@@ -4756,7 +5217,7 @@ void
 ev_check_stop (EV_P_ ev_check *w) EV_NOEXCEPT
 {
   clear_pending (EV_A_ (W)w);
-  if (expect_false (!ev_is_active (w)))
+  if (ecb_expect_false (!ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
@@ -4775,7 +5236,7 @@ ev_check_stop (EV_P_ ev_check *w) EV_NOEXCEPT
 #endif
 
 #if EV_EMBED_ENABLE
-noinline
+ecb_noinline
 void
 ev_embed_sweep (EV_P_ ev_embed *w) EV_NOEXCEPT
 {
@@ -4809,6 +5270,7 @@ embed_prepare_cb (EV_P_ ev_prepare *prepare, int revents)
   }
 }
 
+#if EV_FORK_ENABLE
 static void
 embed_fork_cb (EV_P_ ev_fork *fork_w, int revents)
 {
@@ -4825,6 +5287,7 @@ embed_fork_cb (EV_P_ ev_fork *fork_w, int revents)
 
   ev_embed_start (EV_A_ w);
 }
+#endif
 
 #if 0
 static void
@@ -4837,7 +5300,7 @@ embed_idle_cb (EV_P_ ev_idle *idle, int revents)
 void
 ev_embed_start (EV_P_ ev_embed *w) EV_NOEXCEPT
 {
-  if (expect_false (ev_is_active (w)))
+  if (ecb_expect_false (ev_is_active (w)))
     return;
 
   {
@@ -4855,8 +5318,10 @@ ev_embed_start (EV_P_ ev_embed *w) EV_NOEXCEPT
   ev_set_priority (&w->prepare, EV_MINPRI);
   ev_prepare_start (EV_A_ &w->prepare);
 
+#if EV_FORK_ENABLE
   ev_fork_init (&w->fork, embed_fork_cb);
   ev_fork_start (EV_A_ &w->fork);
+#endif
 
   /*ev_idle_init (&w->idle, e,bed_idle_cb);*/
 
@@ -4869,14 +5334,16 @@ void
 ev_embed_stop (EV_P_ ev_embed *w) EV_NOEXCEPT
 {
   clear_pending (EV_A_ (W)w);
-  if (expect_false (!ev_is_active (w)))
+  if (ecb_expect_false (!ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
 
   ev_io_stop      (EV_A_ &w->io);
   ev_prepare_stop (EV_A_ &w->prepare);
+#if EV_FORK_ENABLE
   ev_fork_stop    (EV_A_ &w->fork);
+#endif
 
   ev_stop (EV_A_ (W)w);
 
@@ -4888,13 +5355,13 @@ ev_embed_stop (EV_P_ ev_embed *w) EV_NOEXCEPT
 void
 ev_fork_start (EV_P_ ev_fork *w) EV_NOEXCEPT
 {
-  if (expect_false (ev_is_active (w)))
+  if (ecb_expect_false (ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
 
   ev_start (EV_A_ (W)w, ++forkcnt);
-  array_needsize (ev_fork *, forks, forkmax, forkcnt, EMPTY2);
+  array_needsize (ev_fork *, forks, forkmax, forkcnt, array_needsize_noinit);
   forks [forkcnt - 1] = w;
 
   EV_FREQUENT_CHECK;
@@ -4904,7 +5371,7 @@ void
 ev_fork_stop (EV_P_ ev_fork *w) EV_NOEXCEPT
 {
   clear_pending (EV_A_ (W)w);
-  if (expect_false (!ev_is_active (w)))
+  if (ecb_expect_false (!ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
@@ -4926,13 +5393,13 @@ ev_fork_stop (EV_P_ ev_fork *w) EV_NOEXCEPT
 void
 ev_cleanup_start (EV_P_ ev_cleanup *w) EV_NOEXCEPT
 {
-  if (expect_false (ev_is_active (w)))
+  if (ecb_expect_false (ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
 
   ev_start (EV_A_ (W)w, ++cleanupcnt);
-  array_needsize (ev_cleanup *, cleanups, cleanupmax, cleanupcnt, EMPTY2);
+  array_needsize (ev_cleanup *, cleanups, cleanupmax, cleanupcnt, array_needsize_noinit);
   cleanups [cleanupcnt - 1] = w;
 
   /* cleanup watchers should never keep a refcount on the loop */
@@ -4944,7 +5411,7 @@ void
 ev_cleanup_stop (EV_P_ ev_cleanup *w) EV_NOEXCEPT
 {
   clear_pending (EV_A_ (W)w);
-  if (expect_false (!ev_is_active (w)))
+  if (ecb_expect_false (!ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
@@ -4967,7 +5434,7 @@ ev_cleanup_stop (EV_P_ ev_cleanup *w) EV_NOEXCEPT
 void
 ev_async_start (EV_P_ ev_async *w) EV_NOEXCEPT
 {
-  if (expect_false (ev_is_active (w)))
+  if (ecb_expect_false (ev_is_active (w)))
     return;
 
   w->sent = 0;
@@ -4977,7 +5444,7 @@ ev_async_start (EV_P_ ev_async *w) EV_NOEXCEPT
   EV_FREQUENT_CHECK;
 
   ev_start (EV_A_ (W)w, ++asynccnt);
-  array_needsize (ev_async *, asyncs, asyncmax, asynccnt, EMPTY2);
+  array_needsize (ev_async *, asyncs, asyncmax, asynccnt, array_needsize_noinit);
   asyncs [asynccnt - 1] = w;
 
   EV_FREQUENT_CHECK;
@@ -4987,7 +5454,7 @@ void
 ev_async_stop (EV_P_ ev_async *w) EV_NOEXCEPT
 {
   clear_pending (EV_A_ (W)w);
-  if (expect_false (!ev_is_active (w)))
+  if (ecb_expect_false (!ev_is_active (w)))
     return;
 
   EV_FREQUENT_CHECK;
@@ -5056,12 +5523,6 @@ ev_once (EV_P_ int fd, int events, ev_tstamp timeout, void (*cb)(int revents, vo
 {
   struct ev_once *once = (struct ev_once *)ev_malloc (sizeof (struct ev_once));
 
-  if (expect_false (!once))
-    {
-      cb (EV_ERROR | EV_READ | EV_WRITE | EV_TIMER, arg);
-      return;
-    }
-
   once->cb  = cb;
   once->arg = arg;
 
@@ -5079,7 +5540,6 @@ ev_once (EV_P_ int fd, int events, ev_tstamp timeout, void (*cb)(int revents, vo
       ev_timer_start (EV_A_ &once->to);
     }
 }
-
 /*****************************************************************************/
 
 #if EV_WALK_ENABLE
@@ -5192,8 +5652,15 @@ ev_walk (EV_P_ int types, void (*cb)(EV_P_ int type, void *w)) EV_NOEXCEPT
           wl = wn;
         }
 #endif
+/* EV_STAT     0x00001000 /* stat data changed */
+/* EV_EMBED    0x00010000 /* embedded event loop needs sweep */
 }
 #endif
+void
+ev_now_update_if_cheap (EV_P) EV_NOEXCEPT
+{
+	if (have_cheap_timer) time_update (EV_A_ 1e100);
+}
 
 #if EV_MULTIPLICITY
   #include "ev_wrap.h"
diff --git a/contrib/libev/ev.h b/contrib/libev/ev.h
index 9d3e4f2fd..7135a08a5 100644
--- a/contrib/libev/ev.h
+++ b/contrib/libev/ev.h
@@ -1,7 +1,7 @@
 /*
  * libev native API header
  *
- * Copyright (c) 2007-2018 Marc Alexander Lehmann <libev@schmorp.de>
+ * Copyright (c) 2007-2020 Marc Alexander Lehmann <libev@schmorp.de>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without modifica-
@@ -151,7 +151,10 @@ EV_CPP(extern "C" {)
 
 /*****************************************************************************/
 
-typedef double ev_tstamp;
+#ifndef EV_TSTAMP_T
+# define EV_TSTAMP_T double
+#endif
+typedef EV_TSTAMP_T ev_tstamp;
 
 #include <string.h> /* for memmove */
 
@@ -212,7 +215,7 @@ struct ev_loop;
 /*****************************************************************************/
 
 #define EV_VERSION_MAJOR 4
-#define EV_VERSION_MINOR 25
+#define EV_VERSION_MINOR 33
 
 /* eventmask, revents, events... */
 enum {
@@ -389,14 +392,12 @@ typedef struct ev_stat
 } ev_stat;
 #endif
 
-#if EV_IDLE_ENABLE
 /* invoked when the nothing else needs to be done, keeps the process from blocking */
 /* revent EV_IDLE */
 typedef struct ev_idle
 {
   EV_WATCHER (ev_idle)
 } ev_idle;
-#endif
 
 /* invoked for each run of the mainloop, just before the blocking call */
 /* you can still change events in any way you like */
@@ -413,23 +414,19 @@ typedef struct ev_check
   EV_WATCHER (ev_check)
 } ev_check;
 
-#if EV_FORK_ENABLE
 /* the callback gets invoked before check in the child process when a fork was detected */
 /* revent EV_FORK */
 typedef struct ev_fork
 {
   EV_WATCHER (ev_fork)
 } ev_fork;
-#endif
 
-#if EV_CLEANUP_ENABLE
 /* is invoked just before the loop gets destroyed */
 /* revent EV_CLEANUP */
 typedef struct ev_cleanup
 {
   EV_WATCHER (ev_cleanup)
 } ev_cleanup;
-#endif
 
 #if EV_EMBED_ENABLE
 /* used to embed an event loop inside another */
@@ -439,16 +436,18 @@ typedef struct ev_embed
   EV_WATCHER (ev_embed)
 
   struct ev_loop *other; /* ro */
+#undef EV_IO_ENABLE
+#define EV_IO_ENABLE 1
   ev_io io;              /* private */
+#undef EV_PREPARE_ENABLE
+#define EV_PREPARE_ENABLE 1
   ev_prepare prepare;    /* private */
   ev_check check;        /* unused */
   ev_timer timer;        /* unused */
   ev_periodic periodic;  /* unused */
   ev_idle idle;          /* unused */
   ev_fork fork;          /* private */
-#if EV_CLEANUP_ENABLE
   ev_cleanup cleanup;    /* unused */
-#endif
 } ev_embed;
 #endif
 
@@ -501,29 +500,32 @@ union ev_any_watcher
 /* flag bits for ev_default_loop and ev_loop_new */
 enum {
   /* the default */
-  EVFLAG_AUTO      = 0x00000000U, /* not quite a mask */
+  EVFLAG_AUTO       = 0x00000000U, /* not quite a mask */
   /* flag bits */
-  EVFLAG_NOENV     = 0x01000000U, /* do NOT consult environment */
-  EVFLAG_FORKCHECK = 0x02000000U, /* check for a fork in each iteration */
+  EVFLAG_NOENV      = 0x01000000U, /* do NOT consult environment */
+  EVFLAG_FORKCHECK  = 0x02000000U, /* check for a fork in each iteration */
   /* debugging/feature disable */
-  EVFLAG_NOINOTIFY = 0x00100000U, /* do not attempt to use inotify */
+  EVFLAG_NOINOTIFY  = 0x00100000U, /* do not attempt to use inotify */
 #if EV_COMPAT3
-  EVFLAG_NOSIGFD   = 0, /* compatibility to pre-3.9 */
+  EVFLAG_NOSIGFD    = 0, /* compatibility to pre-3.9 */
 #endif
-  EVFLAG_SIGNALFD  = 0x00200000U, /* attempt to use signalfd */
-  EVFLAG_NOSIGMASK = 0x00400000U  /* avoid modifying the signal mask */
+  EVFLAG_SIGNALFD   = 0x00200000U, /* attempt to use signalfd */
+  EVFLAG_NOSIGMASK  = 0x00400000U, /* avoid modifying the signal mask */
+  EVFLAG_NOTIMERFD  = 0x00800000U  /* avoid creating a timerfd */
 };
 
 /* method bits to be ored together */
 enum {
-  EVBACKEND_SELECT  = 0x00000001U, /* available just about anywhere */
-  EVBACKEND_POLL    = 0x00000002U, /* !win, !aix, broken on osx */
-  EVBACKEND_EPOLL   = 0x00000004U, /* linux */
-  EVBACKEND_KQUEUE  = 0x00000008U, /* bsd, broken on osx */
-  EVBACKEND_DEVPOLL = 0x00000010U, /* solaris 8 */ /* NYI */
-  EVBACKEND_PORT    = 0x00000020U, /* solaris 10 */
-  EVBACKEND_ALL     = 0x0000003FU, /* all known backends */
-  EVBACKEND_MASK    = 0x0000FFFFU  /* all future backends */
+  EVBACKEND_SELECT   = 0x00000001U, /* available just about anywhere */
+  EVBACKEND_POLL     = 0x00000002U, /* !win, !aix, broken on osx */
+  EVBACKEND_EPOLL    = 0x00000004U, /* linux */
+  EVBACKEND_KQUEUE   = 0x00000008U, /* bsd, broken on osx */
+  EVBACKEND_DEVPOLL  = 0x00000010U, /* solaris 8 */ /* NYI */
+  EVBACKEND_PORT     = 0x00000020U, /* solaris 10 */
+  EVBACKEND_LINUXAIO = 0x00000040U, /* linux AIO, 4.19+ */
+  EVBACKEND_IOURING  = 0x00000080U, /* linux io_uring, 5.1+ */
+  EVBACKEND_ALL      = 0x000000FFU, /* all known backends */
+  EVBACKEND_MASK     = 0x0000FFFFU  /* all future backends */
 };
 
 #if EV_PROTOTYPES
@@ -557,7 +559,6 @@ EV_API_DECL void ev_set_syserr_cb (void (*cb)(const char *msg) EV_NOEXCEPT) EV_N
 /* you can call this as often as you like */
 EV_API_DECL struct ev_loop *ev_default_loop (unsigned int flags EV_CPP (= 0)) EV_NOEXCEPT;
 
-
 /* create and destroy alternative loops that don't handle signals */
 EV_API_DECL struct ev_loop *ev_loop_new (unsigned int flags EV_CPP (= 0)) EV_NOEXCEPT;
 
@@ -643,6 +644,8 @@ EV_API_DECL int ev_active_cnt (EV_P) EV_NOEXCEPT;
  */
 EV_API_DECL void ev_once (EV_P_ int fd, int events, ev_tstamp timeout, void (*cb)(int revents, void *arg), void *arg) EV_NOEXCEPT;
 
+EV_API_DECL void ev_invoke_pending (EV_P); /* invoke all pending watchers */
+
 # if EV_FEATURE_API
 EV_API_DECL unsigned int ev_iteration (EV_P) EV_NOEXCEPT; /* number of loop iterations */
 EV_API_DECL unsigned int ev_depth     (EV_P) EV_NOEXCEPT; /* #ev_loop enters - #ev_loop leaves */
@@ -660,7 +663,6 @@ EV_API_DECL void ev_set_invoke_pending_cb (EV_P_ ev_loop_callback invoke_pending
 EV_API_DECL void ev_set_loop_release_cb (EV_P_ void (*release)(EV_P) EV_NOEXCEPT, void (*acquire)(EV_P) EV_NOEXCEPT) EV_NOEXCEPT;
 
 EV_API_DECL unsigned int ev_pending_count (EV_P) EV_NOEXCEPT; /* number of pending events, if any */
-EV_API_DECL void ev_invoke_pending (EV_P); /* invoke all pending watchers */
 
 /*
  * stop/start the timer handling.
@@ -680,6 +682,7 @@ EV_API_DECL void ev_resume  (EV_P) EV_NOEXCEPT;
   ev_set_cb ((ev), cb_);			\
 } while (0)
 
+#define ev_io_modify(ev,events_)             do { (ev)->events = (ev)->events & EV__IOFDSET | (events_); } while (0)
 #define ev_io_set(ev,fd_,events_)            do { (ev)->fd = (fd_); (ev)->events = (events_) | EV__IOFDSET; } while (0)
 #define ev_timer_set(ev,after_,repeat_)      do { ((ev_watcher_time *)(ev))->at = (after_); (ev)->repeat = (repeat_); } while (0)
 #define ev_periodic_set(ev,ofs_,ival_,rcb_)  do { (ev)->offset = (ofs_); (ev)->interval = (ival_); (ev)->reschedule_cb = (rcb_); } while (0)
@@ -712,7 +715,6 @@ EV_API_DECL void ev_resume  (EV_P) EV_NOEXCEPT;
 #define ev_is_active(ev)                     (0 + ((ev_watcher *)(void *)(ev))->active) /* ro, true when the watcher has been started */
 #define ev_can_stop(ev)                      (ev_is_pending(ev) || ev_is_active(ev)) /* ro, true when the watcher has been started */
 
-
 #define ev_cb_(ev)                           (ev)->cb /* rw */
 #define ev_cb(ev)                            (memmove (&ev_cb_ (ev), &((ev_watcher *)(ev))->cb, sizeof (ev_cb_ (ev))), (ev)->cb)
 
@@ -727,6 +729,7 @@ EV_API_DECL void ev_resume  (EV_P) EV_NOEXCEPT;
 #define ev_periodic_at(ev)                   (+((ev_watcher_time *)(ev))->at)
 
 #ifndef ev_set_cb
+/* memmove is used here to avoid strict aliasing violations, and hopefully is optimized out by any reasonable compiler */
 # define ev_set_cb(ev,cb_)                   (ev_cb_ (ev) = (cb_), memmove (&((ev_watcher *)(ev))->cb, &ev_cb_ (ev), sizeof (ev_cb_ (ev))))
 #endif
 
diff --git a/contrib/libev/ev_epoll.c b/contrib/libev/ev_epoll.c
index 6aef86222..58cfa684d 100644
--- a/contrib/libev/ev_epoll.c
+++ b/contrib/libev/ev_epoll.c
@@ -1,7 +1,7 @@
 /*
  * libev epoll fd activity backend
  *
- * Copyright (c) 2007,2008,2009,2010,2011 Marc Alexander Lehmann <libev@schmorp.de>
+ * Copyright (c) 2007,2008,2009,2010,2011,2016,2017,2019 Marc Alexander Lehmann <libev@schmorp.de>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without modifica-
@@ -93,10 +93,10 @@ epoll_modify (EV_P_ int fd, int oev, int nev)
   ev.events   = (nev & EV_READ  ? EPOLLIN  : 0)
               | (nev & EV_WRITE ? EPOLLOUT : 0);
 
-  if (expect_true (!epoll_ctl (backend_fd, oev && oldmask != nev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev)))
+  if (ecb_expect_true (!epoll_ctl (backend_fd, oev && oldmask != nev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev)))
     return;
 
-  if (expect_true (errno == ENOENT))
+  if (ecb_expect_true (errno == ENOENT))
     {
       /* if ENOENT then the fd went away, so try to do the right thing */
       if (!nev)
@@ -105,7 +105,7 @@ epoll_modify (EV_P_ int fd, int oev, int nev)
       if (!epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev))
         return;
     }
-  else if (expect_true (errno == EEXIST))
+  else if (ecb_expect_true (errno == EEXIST))
     {
       /* EEXIST means we ignored a previous DEL, but the fd is still active */
       /* if the kernel mask is the same as the new mask, we assume it hasn't changed */
@@ -115,7 +115,7 @@ epoll_modify (EV_P_ int fd, int oev, int nev)
       if (!epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev))
         return;
     }
-  else if (expect_true (errno == EPERM))
+  else if (ecb_expect_true (errno == EPERM))
     {
       /* EPERM means the fd is always ready, but epoll is too snobbish */
       /* to handle it, unlike select or poll. */
@@ -124,12 +124,14 @@ epoll_modify (EV_P_ int fd, int oev, int nev)
       /* add fd to epoll_eperms, if not already inside */
       if (!(oldmask & EV_EMASK_EPERM))
         {
-          array_needsize (int, epoll_eperms, epoll_epermmax, epoll_epermcnt + 1, EMPTY2);
+          array_needsize (int, epoll_eperms, epoll_epermmax, epoll_epermcnt + 1, array_needsize_noinit);
           epoll_eperms [epoll_epermcnt++] = fd;
         }
 
       return;
     }
+  else
+    assert (("libev: I/O watcher with invalid fd found in epoll_ctl", errno != EBADF && errno != ELOOP && errno != EINVAL));
 
   fd_kill (EV_A_ fd);
 
@@ -144,16 +146,16 @@ epoll_poll (EV_P_ ev_tstamp timeout)
   int i;
   int eventcnt;
 
-  if (expect_false (epoll_epermcnt))
-    timeout = 0.;
+  if (ecb_expect_false (epoll_epermcnt))
+    timeout = EV_TS_CONST (0.);
 
   /* epoll wait times cannot be larger than (LONG_MAX - 999UL) / HZ msecs, which is below */
   /* the default libev max wait time, however. */
   EV_RELEASE_CB;
-  eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, timeout * 1e3);
+  eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, EV_TS_TO_MSEC (timeout));
   EV_ACQUIRE_CB;
 
-  if (expect_false (eventcnt < 0))
+  if (ecb_expect_false (eventcnt < 0))
     {
       if (errno != EINTR)
         ev_syserr ("(libev) epoll_wait");
@@ -176,14 +178,14 @@ epoll_poll (EV_P_ ev_tstamp timeout)
        * other spurious notifications will be found by epoll_ctl, below
        * we assume that fd is always in range, as we never shrink the anfds array
        */
-      if (expect_false ((uint32_t)anfds [fd].egen != (uint32_t)(ev->data.u64 >> 32)))
+      if (ecb_expect_false ((uint32_t)anfds [fd].egen != (uint32_t)(ev->data.u64 >> 32)))
         {
           /* recreate kernel state */
           postfork |= 2;
           continue;
         }
 
-      if (expect_false (got & ~want))
+      if (ecb_expect_false (got & ~want))
         {
           anfds [fd].emask = want;
 
@@ -195,6 +197,8 @@ epoll_poll (EV_P_ ev_tstamp timeout)
            * above with the gencounter check (== our fd is not the event fd), and
            * partially here, when epoll_ctl returns an error (== a child has the fd
            * but we closed it).
+           * note: for events such as POLLHUP, where we can't know whether it refers
+           * to EV_READ or EV_WRITE, we might issue redundant EPOLL_CTL_MOD calls.
            */
           ev->events = (want & EV_READ  ? EPOLLIN  : 0)
                      | (want & EV_WRITE ? EPOLLOUT : 0);
@@ -212,7 +216,7 @@ epoll_poll (EV_P_ ev_tstamp timeout)
     }
 
   /* if the receive array was full, increase its size */
-  if (expect_false (eventcnt == epoll_eventmax))
+  if (ecb_expect_false (eventcnt == epoll_eventmax))
     {
       ev_free (epoll_events);
       epoll_eventmax = array_nextsize (sizeof (struct epoll_event), epoll_eventmax, epoll_eventmax + 1);
@@ -235,23 +239,34 @@ epoll_poll (EV_P_ ev_tstamp timeout)
     }
 }
 
-inline_size
-int
-epoll_init (EV_P_ int flags)
+static int
+epoll_epoll_create (void)
 {
+  int fd;
+
 #if defined EPOLL_CLOEXEC && !defined __ANDROID__
-  backend_fd = epoll_create1 (EPOLL_CLOEXEC);
+  fd = epoll_create1 (EPOLL_CLOEXEC);
 
-  if (backend_fd < 0 && (errno == EINVAL || errno == ENOSYS))
+  if (fd < 0 && (errno == EINVAL || errno == ENOSYS))
 #endif
-    backend_fd = epoll_create (256);
+    {
+      fd = epoll_create (256);
 
-  if (backend_fd < 0)
-    return 0;
+      if (fd >= 0)
+        fcntl (fd, F_SETFD, FD_CLOEXEC);
+    }
+
+  return fd;
+}
 
-  fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
+inline_size
+int
+epoll_init (EV_P_ int flags)
+{
+  if ((backend_fd = epoll_epoll_create ()) < 0)
+    return 0;
 
-  backend_mintime = 1e-3; /* epoll does sometimes return early, this is just to avoid the worst */
+  backend_mintime = EV_TS_CONST (1e-3); /* epoll does sometimes return early, this is just to avoid the worst */
   backend_modify  = epoll_modify;
   backend_poll    = epoll_poll;
 
@@ -269,17 +284,15 @@ epoll_destroy (EV_P)
   array_free (epoll_eperm, EMPTY);
 }
 
-inline_size
-void
+ecb_cold
+static void
 epoll_fork (EV_P)
 {
   close (backend_fd);
 
-  while ((backend_fd = epoll_create (256)) < 0)
+  while ((backend_fd = epoll_epoll_create ()) < 0)
     ev_syserr ("(libev) epoll_create");
 
-  fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
-
   fd_rearm_all (EV_A);
 }
 
diff --git a/contrib/libev/ev_iouring.c b/contrib/libev/ev_iouring.c
new file mode 100644
index 000000000..bfd3de65f
--- /dev/null
+++ b/contrib/libev/ev_iouring.c
@@ -0,0 +1,694 @@
+/*
+ * libev linux io_uring fd activity backend
+ *
+ * Copyright (c) 2019-2020 Marc Alexander Lehmann <libev@schmorp.de>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modifica-
+ * tion, are permitted provided that the following conditions are met:
+ *
+ *   1.  Redistributions of source code must retain the above copyright notice,
+ *       this list of conditions and the following disclaimer.
+ *
+ *   2.  Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
+ * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO
+ * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
+ * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
+ * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * the GNU General Public License ("GPL") version 2 or any later version,
+ * in which case the provisions of the GPL are applicable instead of
+ * the above. If you wish to allow the use of your version of this file
+ * only under the terms of the GPL and not to allow others to use your
+ * version of this file under the BSD license, indicate your decision
+ * by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL. If you do not delete the
+ * provisions above, a recipient may use your version of this file under
+ * either the BSD or the GPL.
+ */
+
+/*
+ * general notes about linux io_uring:
+ *
+ * a) it's the best interface I have seen so far. on linux.
+ * b) best is not necessarily very good.
+ * c) it's better than the aio mess, doesn't suffer from the fork problems
+ *    of linux aio or epoll and so on and so on. and you could do event stuff
+ *    without any syscalls. what's not to like?
+ * d) ok, it's vastly more complex, but that's ok, really.
+ * e) why two mmaps instead of one? one would be more space-efficient,
+ *    and I can't see what benefit two would have (other than being
+ *    somehow resizable/relocatable, but that's apparently not possible).
+ * f) hmm, it's practically undebuggable (gdb can't access the memory, and
+ *    the bizarre way structure offsets are communicated makes it hard to
+ *    just print the ring buffer heads, even *iff* the memory were visible
+ *    in gdb. but then, that's also ok, really.
+ * g) well, you cannot specify a timeout when waiting for events. no,
+ *    seriously, the interface doesn't support a timeout. never seen _that_
+ *    before. sure, you can use a timerfd, but that's another syscall
+ *    you could have avoided. overall, this bizarre omission smells
+ *    like a µ-optimisation by the io_uring author for his personal
+ *    applications, to the detriment of everybody else who just wants
+ *    an event loop. but, umm, ok, if that's all, it could be worse.
+ *    (from what I gather from the author Jens Axboe, it simply didn't
+ *    occur to him, and he made good on it by adding an unlimited nuber
+ *    of timeouts later :).
+ * h) initially there was a hardcoded limit of 4096 outstanding events.
+ *    later versions not only bump this to 32k, but also can handle
+ *    an unlimited amount of events, so this only affects the batch size.
+ * i) unlike linux aio, you *can* register more then the limit
+ *    of fd events. while early verisons of io_uring signalled an overflow
+ *    and you ended up getting wet. 5.5+ does not do this anymore.
+ * j) but, oh my! it had exactly the same bugs as the linux aio backend,
+ *    where some undocumented poll combinations just fail. fortunately,
+ *    after finally reaching the author, he was more than willing to fix
+ *    this probably in 5.6+.
+ * k) overall, the *API* itself is, I dare to say, not a total trainwreck.
+ *    once the bugs ae fixed (probably in 5.6+), it will be without
+ *    competition.
+ */
+
+/* TODO: use internal TIMEOUT */
+/* TODO: take advantage of single mmap, NODROP etc. */
+/* TODO: resize cq/sq size independently */
+
+#include <sys/timerfd.h>
+#include <sys/mman.h>
+#include <poll.h>
+#include <stdint.h>
+
+#define IOURING_INIT_ENTRIES 32
+
+/*****************************************************************************/
+/* syscall wrapdadoop - this section has the raw api/abi definitions */
+
+#include <linux/fs.h>
+#include <linux/types.h>
+
+/* mostly directly taken from the kernel or documentation */
+
+struct io_uring_sqe
+{
+  __u8 opcode;
+  __u8 flags;
+  __u16 ioprio;
+  __s32 fd;
+  union {
+    __u64 off;
+    __u64 addr2;
+  };
+  __u64 addr;
+  __u32 len;
+  union {
+    __kernel_rwf_t rw_flags;
+    __u32 fsync_flags;
+    __u16 poll_events;
+    __u32 sync_range_flags;
+    __u32 msg_flags;
+    __u32 timeout_flags;
+    __u32 accept_flags;
+    __u32 cancel_flags;
+    __u32 open_flags;
+    __u32 statx_flags;
+  };
+  __u64 user_data;
+  union {
+    __u16 buf_index;
+    __u64 __pad2[3];
+  };
+};
+
+struct io_uring_cqe
+{
+  __u64 user_data;
+  __s32 res;
+  __u32 flags;
+};
+
+struct io_sqring_offsets
+{
+  __u32 head;
+  __u32 tail;
+  __u32 ring_mask;
+  __u32 ring_entries;
+  __u32 flags;
+  __u32 dropped;
+  __u32 array;
+  __u32 resv1;
+  __u64 resv2;
+};
+
+struct io_cqring_offsets
+{
+  __u32 head;
+  __u32 tail;
+  __u32 ring_mask;
+  __u32 ring_entries;
+  __u32 overflow;
+  __u32 cqes;
+  __u64 resv[2];
+};
+
+struct io_uring_params
+{
+  __u32 sq_entries;
+  __u32 cq_entries;
+  __u32 flags;
+  __u32 sq_thread_cpu;
+  __u32 sq_thread_idle;
+  __u32 features;
+  __u32 resv[4];
+  struct io_sqring_offsets sq_off;
+  struct io_cqring_offsets cq_off;
+};
+
+#define IORING_SETUP_CQSIZE 0x00000008
+
+#define IORING_OP_POLL_ADD        6
+#define IORING_OP_POLL_REMOVE     7
+#define IORING_OP_TIMEOUT        11
+#define IORING_OP_TIMEOUT_REMOVE 12
+
+/* relative or absolute, reference clock is CLOCK_MONOTONIC */
+struct iouring_kernel_timespec
+{
+  int64_t tv_sec;
+  long long tv_nsec;
+};
+
+#define IORING_TIMEOUT_ABS 0x00000001
+
+#define IORING_ENTER_GETEVENTS 0x01
+
+#define IORING_OFF_SQ_RING 0x00000000ULL
+#define IORING_OFF_CQ_RING 0x08000000ULL
+#define IORING_OFF_SQES	   0x10000000ULL
+
+#define IORING_FEAT_SINGLE_MMAP   0x00000001
+#define IORING_FEAT_NODROP        0x00000002
+#define IORING_FEAT_SUBMIT_STABLE 0x00000004
+
+inline_size
+int
+evsys_io_uring_setup (unsigned entries, struct io_uring_params *params)
+{
+  return ev_syscall2 (SYS_io_uring_setup, entries, params);
+}
+
+inline_size
+int
+evsys_io_uring_enter (int fd, unsigned to_submit, unsigned min_complete, unsigned flags, const sigset_t *sig, size_t sigsz)
+{
+  return ev_syscall6 (SYS_io_uring_enter, fd, to_submit, min_complete, flags, sig, sigsz);
+}
+
+/*****************************************************************************/
+/* actual backed implementation */
+
+/* we hope that volatile will make the compiler access this variables only once */
+#define EV_SQ_VAR(name) *(volatile unsigned *)((char *)iouring_sq_ring + iouring_sq_ ## name)
+#define EV_CQ_VAR(name) *(volatile unsigned *)((char *)iouring_cq_ring + iouring_cq_ ## name)
+
+/* the index array */
+#define EV_SQ_ARRAY     ((unsigned *)((char *)iouring_sq_ring + iouring_sq_array))
+
+/* the submit/completion queue entries */
+#define EV_SQES         ((struct io_uring_sqe *)         iouring_sqes)
+#define EV_CQES         ((struct io_uring_cqe *)((char *)iouring_cq_ring + iouring_cq_cqes))
+
+inline_speed
+int
+iouring_enter (EV_P_ ev_tstamp timeout)
+{
+  int res;
+
+  EV_RELEASE_CB;
+
+  res = evsys_io_uring_enter (iouring_fd, iouring_to_submit, 1,
+                              timeout > EV_TS_CONST (0.) ? IORING_ENTER_GETEVENTS : 0, 0, 0);
+
+  assert (("libev: io_uring_enter did not consume all sqes", (res < 0 || res == iouring_to_submit)));
+
+  iouring_to_submit = 0;
+
+  EV_ACQUIRE_CB;
+
+  return res;
+}
+
+/* TODO: can we move things around so we don't need this forward-reference? */
+static void
+iouring_poll (EV_P_ ev_tstamp timeout);
+
+static
+struct io_uring_sqe *
+iouring_sqe_get (EV_P)
+{
+  unsigned tail;
+  
+  for (;;)
+    {
+      tail = EV_SQ_VAR (tail);
+
+      if (ecb_expect_true (tail + 1 - EV_SQ_VAR (head) <= EV_SQ_VAR (ring_entries)))
+        break; /* whats the problem, we have free sqes */
+
+      /* queue full, need to flush and possibly handle some events */
+
+#if EV_FEATURE_CODE
+      /* first we ask the kernel nicely, most often this frees up some sqes */
+      int res = iouring_enter (EV_A_ EV_TS_CONST (0.));
+
+      ECB_MEMORY_FENCE_ACQUIRE; /* better safe than sorry */
+
+      if (res >= 0)
+        continue; /* yes, it worked, try again */
+#endif
+
+      /* some problem, possibly EBUSY - do the full poll and let it handle any issues */
+
+      iouring_poll (EV_A_ EV_TS_CONST (0.));
+      /* iouring_poll should have done ECB_MEMORY_FENCE_ACQUIRE for us */
+    }
+
+  /*assert (("libev: io_uring queue full after flush", tail + 1 - EV_SQ_VAR (head) <= EV_SQ_VAR (ring_entries)));*/
+
+  return EV_SQES + (tail & EV_SQ_VAR (ring_mask));
+}
+
+inline_size
+struct io_uring_sqe *
+iouring_sqe_submit (EV_P_ struct io_uring_sqe *sqe)
+{
+  unsigned idx = sqe - EV_SQES;
+
+  EV_SQ_ARRAY [idx] = idx;
+  ECB_MEMORY_FENCE_RELEASE;
+  ++EV_SQ_VAR (tail);
+  /*ECB_MEMORY_FENCE_RELEASE; /* for the time being we assume this is not needed */
+  ++iouring_to_submit;
+}
+
+/*****************************************************************************/
+
+/* when the timerfd expires we simply note the fact,
+ * as the purpose of the timerfd is to wake us up, nothing else.
+ * the next iteration should re-set it.
+ */
+static void
+iouring_tfd_cb (EV_P_ struct ev_io *w, int revents)
+{
+  iouring_tfd_to = EV_TSTAMP_HUGE;
+}
+
+/* called for full and partial cleanup */
+ecb_cold
+static int
+iouring_internal_destroy (EV_P)
+{
+  close (iouring_tfd);
+  close (iouring_fd);
+
+  if (iouring_sq_ring != MAP_FAILED) munmap (iouring_sq_ring, iouring_sq_ring_size);
+  if (iouring_cq_ring != MAP_FAILED) munmap (iouring_cq_ring, iouring_cq_ring_size);
+  if (iouring_sqes    != MAP_FAILED) munmap (iouring_sqes   , iouring_sqes_size   );
+
+  if (ev_is_active (&iouring_tfd_w))
+    {
+      ev_ref (EV_A);
+      ev_io_stop (EV_A_ &iouring_tfd_w);
+    }
+}
+
+ecb_cold
+static int
+iouring_internal_init (EV_P)
+{
+  struct io_uring_params params = { 0 };
+
+  iouring_to_submit = 0;
+
+  iouring_tfd     = -1;
+  iouring_sq_ring = MAP_FAILED;
+  iouring_cq_ring = MAP_FAILED;
+  iouring_sqes    = MAP_FAILED;
+
+  if (!have_monotonic) /* cannot really happen, but what if11 */
+    return -1;
+
+  for (;;)
+    {
+      iouring_fd = evsys_io_uring_setup (iouring_entries, &params);
+
+      if (iouring_fd >= 0)
+        break; /* yippie */
+
+      if (errno != EINVAL)
+        return -1; /* we failed */
+
+#if TODO
+      if ((~params.features) & (IORING_FEAT_NODROP | IORING_FEATURE_SINGLE_MMAP | IORING_FEAT_SUBMIT_STABLE))
+        return -1; /* we require the above features */
+#endif
+
+      /* EINVAL: lots of possible reasons, but maybe
+       * it is because we hit the unqueryable hardcoded size limit
+       */
+
+      /* we hit the limit already, give up */
+      if (iouring_max_entries)
+        return -1;
+
+      /* first time we hit EINVAL? assume we hit the limit, so go back and retry */
+      iouring_entries >>= 1;
+      iouring_max_entries = iouring_entries;
+    }
+
+  iouring_sq_ring_size = params.sq_off.array + params.sq_entries * sizeof (unsigned);
+  iouring_cq_ring_size = params.cq_off.cqes  + params.cq_entries * sizeof (struct io_uring_cqe);
+  iouring_sqes_size    =                       params.sq_entries * sizeof (struct io_uring_sqe);
+
+  iouring_sq_ring = mmap (0, iouring_sq_ring_size, PROT_READ | PROT_WRITE,
+                          MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_SQ_RING);
+  iouring_cq_ring = mmap (0, iouring_cq_ring_size, PROT_READ | PROT_WRITE,
+                          MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_CQ_RING);
+  iouring_sqes    = mmap (0, iouring_sqes_size, PROT_READ | PROT_WRITE,
+                          MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_SQES);
+
+  if (iouring_sq_ring == MAP_FAILED || iouring_cq_ring == MAP_FAILED || iouring_sqes == MAP_FAILED)
+    return -1;
+
+  iouring_sq_head         = params.sq_off.head;
+  iouring_sq_tail         = params.sq_off.tail;
+  iouring_sq_ring_mask    = params.sq_off.ring_mask;
+  iouring_sq_ring_entries = params.sq_off.ring_entries;
+  iouring_sq_flags        = params.sq_off.flags;
+  iouring_sq_dropped      = params.sq_off.dropped;
+  iouring_sq_array        = params.sq_off.array;
+
+  iouring_cq_head         = params.cq_off.head;
+  iouring_cq_tail         = params.cq_off.tail;
+  iouring_cq_ring_mask    = params.cq_off.ring_mask;
+  iouring_cq_ring_entries = params.cq_off.ring_entries;
+  iouring_cq_overflow     = params.cq_off.overflow;
+  iouring_cq_cqes         = params.cq_off.cqes;
+
+  iouring_tfd = timerfd_create (CLOCK_MONOTONIC, TFD_CLOEXEC);
+
+  if (iouring_tfd < 0)
+    return iouring_tfd;
+
+  iouring_tfd_to = EV_TSTAMP_HUGE;
+
+  return 0;
+}
+
+ecb_cold
+static void
+iouring_fork (EV_P)
+{
+  iouring_internal_destroy (EV_A);
+
+  while (iouring_internal_init (EV_A) < 0)
+    ev_syserr ("(libev) io_uring_setup");
+
+  fd_rearm_all (EV_A);
+
+  ev_io_stop  (EV_A_ &iouring_tfd_w);
+  ev_io_set   (EV_A_ &iouring_tfd_w, iouring_tfd, EV_READ);
+  ev_io_start (EV_A_ &iouring_tfd_w);
+}
+
+/*****************************************************************************/
+
+static void
+iouring_modify (EV_P_ int fd, int oev, int nev)
+{
+  if (oev)
+    {
+      /* we assume the sqe's are all "properly" initialised */
+      struct io_uring_sqe *sqe = iouring_sqe_get (EV_A);
+      sqe->opcode    = IORING_OP_POLL_REMOVE;
+      sqe->fd        = fd;
+      /* Jens Axboe notified me that user_data is not what is documented, but is
+       * some kind of unique ID that has to match, otherwise the request cannot
+       * be removed. Since we don't *really* have that, we pass in the old
+       * generation counter - if that fails, too bad, it will hopefully be removed
+       * at close time and then be ignored. */
+      sqe->addr      = (uint32_t)fd | ((__u64)(uint32_t)anfds [fd].egen << 32);
+      sqe->user_data = (uint64_t)-1;
+      iouring_sqe_submit (EV_A_ sqe);
+
+      /* increment generation counter to avoid handling old events */
+      ++anfds [fd].egen;
+    }
+
+  if (nev)
+    {
+      struct io_uring_sqe *sqe = iouring_sqe_get (EV_A);
+      sqe->opcode      = IORING_OP_POLL_ADD;
+      sqe->fd          = fd;
+      sqe->addr        = 0;
+      sqe->user_data   = (uint32_t)fd | ((__u64)(uint32_t)anfds [fd].egen << 32);
+      sqe->poll_events =
+        (nev & EV_READ ? POLLIN : 0)
+        | (nev & EV_WRITE ? POLLOUT : 0);
+      iouring_sqe_submit (EV_A_ sqe);
+    }
+}
+
+inline_size
+void
+iouring_tfd_update (EV_P_ ev_tstamp timeout)
+{
+  ev_tstamp tfd_to = mn_now + timeout;
+
+  /* we assume there will be many iterations per timer change, so
+   * we only re-set the timerfd when we have to because its expiry
+   * is too late.
+   */
+  if (ecb_expect_false (tfd_to < iouring_tfd_to))
+    {
+       struct itimerspec its;
+
+       iouring_tfd_to = tfd_to;
+       EV_TS_SET (its.it_interval, 0.);
+       EV_TS_SET (its.it_value, tfd_to);
+
+       if (timerfd_settime (iouring_tfd, TFD_TIMER_ABSTIME, &its, 0) < 0)
+         assert (("libev: iouring timerfd_settime failed", 0));
+    }
+}
+
+inline_size
+void
+iouring_process_cqe (EV_P_ struct io_uring_cqe *cqe)
+{
+  int      fd  = cqe->user_data & 0xffffffffU;
+  uint32_t gen = cqe->user_data >> 32;
+  int      res = cqe->res;
+
+  /* user_data -1 is a remove that we are not atm. interested in */
+  if (cqe->user_data == (uint64_t)-1)
+    return;
+
+  assert (("libev: io_uring fd must be in-bounds", fd >= 0 && fd < anfdmax));
+
+  /* documentation lies, of course. the result value is NOT like
+   * normal syscalls, but like linux raw syscalls, i.e. negative
+   * error numbers. fortunate, as otherwise there would be no way
+   * to get error codes at all. still, why not document this?
+   */
+
+  /* ignore event if generation doesn't match */
+  /* other than skipping removal events, */
+  /* this should actually be very rare */
+  if (ecb_expect_false (gen != (uint32_t)anfds [fd].egen))
+    return;
+
+  if (ecb_expect_false (res < 0))
+    {
+      /*TODO: EINVAL handling (was something failed with this fd)*/
+
+      if (res == -EBADF)
+        {
+          assert (("libev: event loop rejected bad fd", res != -EBADF));
+          fd_kill (EV_A_ fd);
+        }
+      else
+        {
+          errno = -res;
+          ev_syserr ("(libev) IORING_OP_POLL_ADD");
+        }
+
+      return;
+    }
+
+  /* feed events, we do not expect or handle POLLNVAL */
+  fd_event (
+    EV_A_
+    fd,
+    (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0)
+    | (res & (POLLIN | POLLERR | POLLHUP) ? EV_READ : 0)
+  );
+
+  /* io_uring is oneshot, so we need to re-arm the fd next iteration */
+  /* this also means we usually have to do at least one syscall per iteration */
+  anfds [fd].events = 0;
+  fd_change (EV_A_ fd, EV_ANFD_REIFY);
+}
+
+/* called when the event queue overflows */
+ecb_cold
+static void
+iouring_overflow (EV_P)
+{
+  /* we have two options, resize the queue (by tearing down
+   * everything and recreating it, or living with it
+   * and polling.
+   * we implement this by resizing the queue, and, if that fails,
+   * we just recreate the state on every failure, which
+   * kind of is a very inefficient poll.
+   * one danger is, due to the bios toward lower fds,
+   * we will only really get events for those, so
+   * maybe we need a poll() fallback, after all.
+   */
+  /*EV_CQ_VAR (overflow) = 0;*/ /* need to do this if we keep the state and poll manually */
+
+  fd_rearm_all (EV_A);
+
+  /* we double the size until we hit the hard-to-probe maximum */
+  if (!iouring_max_entries)
+    {
+      iouring_entries <<= 1;
+      iouring_fork (EV_A);
+    }
+  else
+    {
+      /* we hit the kernel limit, we should fall back to something else.
+       * we can either poll() a few times and hope for the best,
+       * poll always, or switch to epoll.
+       * TODO: is this necessary with newer kernels?
+       */
+
+      iouring_internal_destroy (EV_A);
+
+      /* this should make it so that on return, we don't call any uring functions */
+      iouring_to_submit = 0;
+
+      for (;;)
+        {
+          backend = epoll_init (EV_A_ 0);
+
+          if (backend)
+            break;
+
+          ev_syserr ("(libev) iouring switch to epoll");
+        }
+    }
+}
+
+/* handle any events in the completion queue, return true if there were any */
+static int
+iouring_handle_cq (EV_P)
+{
+  unsigned head, tail, mask;
+  
+  head = EV_CQ_VAR (head);
+  ECB_MEMORY_FENCE_ACQUIRE;
+  tail = EV_CQ_VAR (tail);
+
+  if (head == tail)
+    return 0;
+
+  /* it can only overflow if we have events, yes, yes? */
+  if (ecb_expect_false (EV_CQ_VAR (overflow)))
+    {
+      iouring_overflow (EV_A);
+      return 1;
+    }
+
+  mask = EV_CQ_VAR (ring_mask);
+
+  do
+    iouring_process_cqe (EV_A_ &EV_CQES [head++ & mask]);
+  while (head != tail);
+
+  EV_CQ_VAR (head) = head;
+  ECB_MEMORY_FENCE_RELEASE;
+
+  return 1;
+}
+
+static void
+iouring_poll (EV_P_ ev_tstamp timeout)
+{
+  /* if we have events, no need for extra syscalls, but we might have to queue events */
+  /* we also clar the timeout if there are outstanding fdchanges */
+  /* the latter should only happen if both the sq and cq are full, most likely */
+  /* because we have a lot of event sources that immediately complete */
+  /* TODO: fdchacngecnt is always 0 because fd_reify does not have two buffers yet */
+  if (iouring_handle_cq (EV_A) || fdchangecnt)
+    timeout = EV_TS_CONST (0.);
+  else
+    /* no events, so maybe wait for some */
+    iouring_tfd_update (EV_A_ timeout);
+
+  /* only enter the kernel if we have something to submit, or we need to wait */
+  if (timeout || iouring_to_submit)
+    {
+      int res = iouring_enter (EV_A_ timeout);
+
+      if (ecb_expect_false (res < 0))
+        if (errno == EINTR)
+          /* ignore */;
+        else if (errno == EBUSY)
+          /* cq full, cannot submit - should be rare because we flush the cq first, so simply ignore */;
+        else
+          ev_syserr ("(libev) iouring setup");
+      else
+        iouring_handle_cq (EV_A);
+    }
+}
+
+inline_size
+int
+iouring_init (EV_P_ int flags)
+{
+  iouring_entries     = IOURING_INIT_ENTRIES;
+  iouring_max_entries = 0;
+
+  if (iouring_internal_init (EV_A) < 0)
+    {
+      iouring_internal_destroy (EV_A);
+      return 0;
+    }
+
+  ev_io_init  (&iouring_tfd_w, iouring_tfd_cb, iouring_tfd, EV_READ);
+  ev_set_priority (&iouring_tfd_w, EV_MINPRI);
+  ev_io_start (EV_A_ &iouring_tfd_w);
+  ev_unref (EV_A); /* watcher should not keep loop alive */
+
+  backend_modify = iouring_modify;
+  backend_poll   = iouring_poll;
+
+  return EVBACKEND_IOURING;
+}
+
+inline_size
+void
+iouring_destroy (EV_P)
+{
+  iouring_internal_destroy (EV_A);
+}
+
diff --git a/contrib/libev/ev_kqueue.c b/contrib/libev/ev_kqueue.c
index 0c05ab9e7..69c5147f1 100644
--- a/contrib/libev/ev_kqueue.c
+++ b/contrib/libev/ev_kqueue.c
@@ -1,7 +1,7 @@
 /*
  * libev kqueue backend
  *
- * Copyright (c) 2007,2008,2009,2010,2011,2012,2013 Marc Alexander Lehmann <libev@schmorp.de>
+ * Copyright (c) 2007,2008,2009,2010,2011,2012,2013,2016,2019 Marc Alexander Lehmann <libev@schmorp.de>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without modifica-
@@ -48,7 +48,7 @@ void
 kqueue_change (EV_P_ int fd, int filter, int flags, int fflags)
 {
   ++kqueue_changecnt;
-  array_needsize (struct kevent, kqueue_changes, kqueue_changemax, kqueue_changecnt, EMPTY2);
+  array_needsize (struct kevent, kqueue_changes, kqueue_changemax, kqueue_changecnt, array_needsize_noinit);
 
   EV_SET (&kqueue_changes [kqueue_changecnt - 1], fd, filter, flags, fflags, 0, 0);
 }
@@ -103,10 +103,10 @@ kqueue_poll (EV_P_ ev_tstamp timeout)
   EV_ACQUIRE_CB;
   kqueue_changecnt = 0;
 
-  if (expect_false (res < 0))
+  if (ecb_expect_false (res < 0))
     {
       if (errno != EINTR)
-        ev_syserr ("(libev) kevent");
+        ev_syserr ("(libev) kqueue kevent");
 
       return;
     }
@@ -115,7 +115,7 @@ kqueue_poll (EV_P_ ev_tstamp timeout)
     {
       int fd = kqueue_events [i].ident;
 
-      if (expect_false (kqueue_events [i].flags & EV_ERROR))
+      if (ecb_expect_false (kqueue_events [i].flags & EV_ERROR))
         {
           int err = kqueue_events [i].data;
 
@@ -129,10 +129,16 @@ kqueue_poll (EV_P_ ev_tstamp timeout)
                   if (fd_valid (fd))
                     kqueue_modify (EV_A_ fd, 0, anfds [fd].events);
                   else
-                    fd_kill (EV_A_ fd);
+                    {
+                      assert (("libev: kqueue found invalid fd", 0));
+                      fd_kill (EV_A_ fd);
+                    }
                 }
               else /* on all other errors, we error out on the fd */
-                fd_kill (EV_A_ fd);
+                {
+                  assert (("libev: kqueue found invalid fd", 0));
+                  fd_kill (EV_A_ fd);
+                }
             }
         }
       else
@@ -145,7 +151,7 @@ kqueue_poll (EV_P_ ev_tstamp timeout)
         );
     }
 
-  if (expect_false (res == kqueue_eventmax))
+  if (ecb_expect_false (res == kqueue_eventmax))
     {
       ev_free (kqueue_events);
       kqueue_eventmax = array_nextsize (sizeof (struct kevent), kqueue_eventmax, kqueue_eventmax + 1);
@@ -164,7 +170,7 @@ kqueue_init (EV_P_ int flags)
 
   fcntl (backend_fd, F_SETFD, FD_CLOEXEC); /* not sure if necessary, hopefully doesn't hurt */
 
-  backend_mintime = 1e-9; /* apparently, they did the right thing in freebsd */
+  backend_mintime = EV_TS_CONST (1e-9); /* apparently, they did the right thing in freebsd */
   backend_modify  = kqueue_modify;
   backend_poll    = kqueue_poll;
 
diff --git a/contrib/libev/ev_linuxaio.c b/contrib/libev/ev_linuxaio.c
new file mode 100644
index 000000000..4687a703e
--- /dev/null
+++ b/contrib/libev/ev_linuxaio.c
@@ -0,0 +1,620 @@
+/*
+ * libev linux aio fd activity backend
+ *
+ * Copyright (c) 2019 Marc Alexander Lehmann <libev@schmorp.de>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modifica-
+ * tion, are permitted provided that the following conditions are met:
+ *
+ *   1.  Redistributions of source code must retain the above copyright notice,
+ *       this list of conditions and the following disclaimer.
+ *
+ *   2.  Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
+ * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO
+ * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
+ * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
+ * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * the GNU General Public License ("GPL") version 2 or any later version,
+ * in which case the provisions of the GPL are applicable instead of
+ * the above. If you wish to allow the use of your version of this file
+ * only under the terms of the GPL and not to allow others to use your
+ * version of this file under the BSD license, indicate your decision
+ * by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL. If you do not delete the
+ * provisions above, a recipient may use your version of this file under
+ * either the BSD or the GPL.
+ */
+
+/*
+ * general notes about linux aio:
+ *
+ * a) at first, the linux aio IOCB_CMD_POLL functionality introduced in
+ *    4.18 looks too good to be true: both watchers and events can be
+ *    batched, and events can even be handled in userspace using
+ *    a ring buffer shared with the kernel. watchers can be canceled
+ *    regardless of whether the fd has been closed. no problems with fork.
+ *    ok, the ring buffer is 200% undocumented (there isn't even a
+ *    header file), but otherwise, it's pure bliss!
+ * b) ok, watchers are one-shot, so you have to re-arm active ones
+ *    on every iteration. so much for syscall-less event handling,
+ *    but at least these re-arms can be batched, no big deal, right?
+ * c) well, linux as usual: the documentation lies to you: io_submit
+ *    sometimes returns EINVAL because the kernel doesn't feel like
+ *    handling your poll mask - ttys can be polled for POLLOUT,
+ *    POLLOUT|POLLIN, but polling for POLLIN fails. just great,
+ *    so we have to fall back to something else (hello, epoll),
+ *    but at least the fallback can be slow, because these are
+ *    exceptional cases, right?
+ * d) hmm, you have to tell the kernel the maximum number of watchers
+ *    you want to queue when initialising the aio context. but of
+ *    course the real limit is magically calculated in the kernel, and
+ *    is often higher then we asked for. so we just have to destroy
+ *    the aio context and re-create it a bit larger if we hit the limit.
+ *    (starts to remind you of epoll? well, it's a bit more deterministic
+ *    and less gambling, but still ugly as hell).
+ * e) that's when you find out you can also hit an arbitrary system-wide
+ *    limit. or the kernel simply doesn't want to handle your watchers.
+ *    what the fuck do we do then? you guessed it, in the middle
+ *    of event handling we have to switch to 100% epoll polling. and
+ *    that better is as fast as normal epoll polling, so you practically
+ *    have to use the normal epoll backend with all its quirks.
+ * f) end result of this train wreck: it inherits all the disadvantages
+ *    from epoll, while adding a number on its own. why even bother to use
+ *    it? because if conditions are right and your fds are supported and you
+ *    don't hit a limit, this backend is actually faster, doesn't gamble with
+ *    your fds, batches watchers and events and doesn't require costly state
+ *    recreates. well, until it does.
+ * g) all of this makes this backend use almost twice as much code as epoll.
+ *    which in turn uses twice as much code as poll. and that#s not counting
+ *    the fact that this backend also depends on the epoll backend, making
+ *    it three times as much code as poll, or kqueue.
+ * h) bleah. why can't linux just do kqueue. sure kqueue is ugly, but by now
+ *    it's clear that whatever linux comes up with is far, far, far worse.
+ */
+
+#include <sys/time.h> /* actually linux/time.h, but we must assume they are compatible */
+#include <poll.h>
+#include <linux/aio_abi.h>
+
+/*****************************************************************************/
+/* syscall wrapdadoop - this section has the raw api/abi definitions */
+
+#include <sys/syscall.h> /* no glibc wrappers */
+
+/* aio_abi.h is not versioned in any way, so we cannot test for its existance */
+#define IOCB_CMD_POLL 5
+
+/* taken from linux/fs/aio.c. yup, that's a .c file.
+ * not only is this totally undocumented, not even the source code
+ * can tell you what the future semantics of compat_features and
+ * incompat_features are, or what header_length actually is for.
+ */
+#define AIO_RING_MAGIC                  0xa10a10a1
+#define EV_AIO_RING_INCOMPAT_FEATURES   0
+struct aio_ring
+{
+  unsigned id;    /* kernel internal index number */
+  unsigned nr;    /* number of io_events */
+  unsigned head;  /* Written to by userland or by kernel. */
+  unsigned tail;
+
+  unsigned magic;
+  unsigned compat_features;
+  unsigned incompat_features;
+  unsigned header_length;  /* size of aio_ring */
+
+  struct io_event io_events[0];
+};
+
+inline_size
+int
+evsys_io_setup (unsigned nr_events, aio_context_t *ctx_idp)
+{
+  return ev_syscall2 (SYS_io_setup, nr_events, ctx_idp);
+}
+
+inline_size
+int
+evsys_io_destroy (aio_context_t ctx_id)
+{
+  return ev_syscall1 (SYS_io_destroy, ctx_id);
+}
+
+inline_size
+int
+evsys_io_submit (aio_context_t ctx_id, long nr, struct iocb *cbp[])
+{
+  return ev_syscall3 (SYS_io_submit, ctx_id, nr, cbp);
+}
+
+inline_size
+int
+evsys_io_cancel (aio_context_t ctx_id, struct iocb *cbp, struct io_event *result)
+{
+  return ev_syscall3 (SYS_io_cancel, ctx_id, cbp, result);
+}
+
+inline_size
+int
+evsys_io_getevents (aio_context_t ctx_id, long min_nr, long nr, struct io_event *events, struct timespec *timeout)
+{
+  return ev_syscall5 (SYS_io_getevents, ctx_id, min_nr, nr, events, timeout);
+}
+
+/*****************************************************************************/
+/* actual backed implementation */
+
+ecb_cold
+static int
+linuxaio_nr_events (EV_P)
+{
+  /* we start with 16 iocbs and incraese from there
+   * that's tiny, but the kernel has a rather low system-wide
+   * limit that can be reached quickly, so let's be parsimonious
+   * with this resource.
+   * Rest assured, the kernel generously rounds up small and big numbers
+   * in different ways (but doesn't seem to charge you for it).
+   * The 15 here is because the kernel usually has a power of two as aio-max-nr,
+   * and this helps to take advantage of that limit.
+   */
+
+  /* we try to fill 4kB pages exactly.
+   * the ring buffer header is 32 bytes, every io event is 32 bytes.
+   * the kernel takes the io requests number, doubles it, adds 2
+   * and adds the ring buffer.
+   * the way we use this is by starting low, and then roughly doubling the
+   * size each time we hit a limit.
+   */
+
+  int requests   = 15 << linuxaio_iteration;
+  int one_page   =  (4096
+                    / sizeof (struct io_event)    ) / 2; /* how many fit into one page */
+  int first_page = ((4096 - sizeof (struct aio_ring))
+                    / sizeof (struct io_event) - 2) / 2; /* how many fit into the first page */
+
+  /* if everything fits into one page, use count exactly */
+  if (requests > first_page)
+    /* otherwise, round down to full pages and add the first page */
+    requests = requests / one_page * one_page + first_page;
+
+  return requests;
+}
+
+/* we use out own wrapper structure in case we ever want to do something "clever" */
+typedef struct aniocb
+{
+  struct iocb io;
+  /*int inuse;*/
+} *ANIOCBP;
+
+inline_size
+void
+linuxaio_array_needsize_iocbp (ANIOCBP *base, int offset, int count)
+{
+  while (count--)
+    {
+      /* TODO: quite the overhead to allocate every iocb separately, maybe use our own allocator? */
+      ANIOCBP iocb = (ANIOCBP)ev_malloc (sizeof (*iocb));
+
+      /* full zero initialise is probably not required at the moment, but
+       * this is not well documented, so we better do it.
+       */
+      memset (iocb, 0, sizeof (*iocb));
+
+      iocb->io.aio_lio_opcode = IOCB_CMD_POLL;
+      iocb->io.aio_fildes     = offset;
+
+      base [offset++] = iocb;
+    }
+}
+
+ecb_cold
+static void
+linuxaio_free_iocbp (EV_P)
+{
+  while (linuxaio_iocbpmax--)
+    ev_free (linuxaio_iocbps [linuxaio_iocbpmax]);
+
+  linuxaio_iocbpmax = 0; /* next resize will completely reallocate the array, at some overhead */
+}
+
+static void
+linuxaio_modify (EV_P_ int fd, int oev, int nev)
+{
+  array_needsize (ANIOCBP, linuxaio_iocbps, linuxaio_iocbpmax, fd + 1, linuxaio_array_needsize_iocbp);
+  ANIOCBP iocb = linuxaio_iocbps [fd];
+  ANFD *anfd = &anfds [fd];
+
+  if (ecb_expect_false (iocb->io.aio_reqprio < 0))
+    {
+      /* we handed this fd over to epoll, so undo this first */
+      /* we do it manually because the optimisations on epoll_modify won't do us any good */
+      epoll_ctl (backend_fd, EPOLL_CTL_DEL, fd, 0);
+      anfd->emask = 0;
+      iocb->io.aio_reqprio = 0;
+    }
+  else if (ecb_expect_false (iocb->io.aio_buf))
+    {
+      /* iocb active, so cancel it first before resubmit */
+      /* this assumes we only ever get one call per fd per loop iteration */
+      for (;;)
+        {
+          /* on all relevant kernels, io_cancel fails with EINPROGRESS on "success" */
+          if (ecb_expect_false (evsys_io_cancel (linuxaio_ctx, &iocb->io, (struct io_event *)0) == 0))
+            break;
+
+          if (ecb_expect_true (errno == EINPROGRESS))
+            break;
+
+          /* the EINPROGRESS test is for nicer error message. clumsy. */
+          if (errno != EINTR)
+            {
+              assert (("libev: linuxaio unexpected io_cancel failed", errno != EINTR && errno != EINPROGRESS));
+              break;
+            }
+       }
+
+      /* increment generation counter to avoid handling old events */
+      ++anfd->egen;
+    }
+
+  iocb->io.aio_buf = (nev & EV_READ  ? POLLIN  : 0)
+                   | (nev & EV_WRITE ? POLLOUT : 0);
+
+  if (nev)
+    {
+      iocb->io.aio_data = (uint32_t)fd | ((__u64)(uint32_t)anfd->egen << 32);
+
+      /* queue iocb up for io_submit */
+      /* this assumes we only ever get one call per fd per loop iteration */
+      ++linuxaio_submitcnt;
+      array_needsize (struct iocb *, linuxaio_submits, linuxaio_submitmax, linuxaio_submitcnt, array_needsize_noinit);
+      linuxaio_submits [linuxaio_submitcnt - 1] = &iocb->io;
+    }
+}
+
+static void
+linuxaio_epoll_cb (EV_P_ struct ev_io *w, int revents)
+{
+  epoll_poll (EV_A_ 0);
+}
+
+inline_speed
+void
+linuxaio_fd_rearm (EV_P_ int fd)
+{
+  anfds [fd].events = 0;
+  linuxaio_iocbps [fd]->io.aio_buf = 0;
+  fd_change (EV_A_ fd, EV_ANFD_REIFY);
+}
+
+static void
+linuxaio_parse_events (EV_P_ struct io_event *ev, int nr)
+{
+  while (nr)
+    {
+      int fd       = ev->data & 0xffffffff;
+      uint32_t gen = ev->data >> 32;
+      int res      = ev->res;
+
+      assert (("libev: iocb fd must be in-bounds", fd >= 0 && fd < anfdmax));
+
+      /* only accept events if generation counter matches */
+      if (ecb_expect_true (gen == (uint32_t)anfds [fd].egen))
+        {
+          /* feed events, we do not expect or handle POLLNVAL */
+          fd_event (
+            EV_A_
+            fd,
+            (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0)
+            | (res & (POLLIN | POLLERR | POLLHUP) ? EV_READ : 0)
+          );
+
+          /* linux aio is oneshot: rearm fd. TODO: this does more work than strictly needed */
+          linuxaio_fd_rearm (EV_A_ fd);
+        }
+
+      --nr;
+      ++ev;
+    }
+}
+
+/* get any events from ring buffer, return true if any were handled */
+static int
+linuxaio_get_events_from_ring (EV_P)
+{
+  struct aio_ring *ring = (struct aio_ring *)linuxaio_ctx;
+  unsigned head, tail;
+
+  /* the kernel reads and writes both of these variables, */
+  /* as a C extension, we assume that volatile use here */
+  /* both makes reads atomic and once-only */
+  head = *(volatile unsigned *)&ring->head;
+  ECB_MEMORY_FENCE_ACQUIRE;
+  tail = *(volatile unsigned *)&ring->tail;
+
+  if (head == tail)
+    return 0;
+
+  /* parse all available events, but only once, to avoid starvation */
+  if (ecb_expect_true (tail > head)) /* normal case around */
+    linuxaio_parse_events (EV_A_ ring->io_events + head, tail - head);
+  else /* wrapped around */
+    {
+      linuxaio_parse_events (EV_A_ ring->io_events + head, ring->nr - head);
+      linuxaio_parse_events (EV_A_ ring->io_events, tail);
+    }
+
+  ECB_MEMORY_FENCE_RELEASE;
+  /* as an extension to C, we hope that the volatile will make this atomic and once-only */
+  *(volatile unsigned *)&ring->head = tail;
+
+  return 1;
+}
+
+inline_size
+int
+linuxaio_ringbuf_valid (EV_P)
+{
+  struct aio_ring *ring = (struct aio_ring *)linuxaio_ctx;
+
+  return ecb_expect_true (ring->magic == AIO_RING_MAGIC)
+                      && ring->incompat_features == EV_AIO_RING_INCOMPAT_FEATURES
+                      && ring->header_length == sizeof (struct aio_ring); /* TODO: or use it to find io_event[0]? */
+}
+
+/* read at least one event from kernel, or timeout */
+inline_size
+void
+linuxaio_get_events (EV_P_ ev_tstamp timeout)
+{
+  struct timespec ts;
+  struct io_event ioev[8]; /* 256 octet stack space */
+  int want = 1; /* how many events to request */
+  int ringbuf_valid = linuxaio_ringbuf_valid (EV_A);
+
+  if (ecb_expect_true (ringbuf_valid))
+    {
+      /* if the ring buffer has any events, we don't wait or call the kernel at all */
+      if (linuxaio_get_events_from_ring (EV_A))
+        return;
+
+      /* if the ring buffer is empty, and we don't have a timeout, then don't call the kernel */
+      if (!timeout)
+        return;
+    }
+  else
+    /* no ringbuffer, request slightly larger batch */
+    want = sizeof (ioev) / sizeof (ioev [0]);
+
+  /* no events, so wait for some
+   * for fairness reasons, we do this in a loop, to fetch all events
+   */
+  for (;;)
+    {
+      int res;
+
+      EV_RELEASE_CB;
+
+      EV_TS_SET (ts, timeout);
+      res = evsys_io_getevents (linuxaio_ctx, 1, want, ioev, &ts);
+
+      EV_ACQUIRE_CB;
+
+      if (res < 0)
+        if (errno == EINTR)
+          /* ignored, retry */;
+        else
+          ev_syserr ("(libev) linuxaio io_getevents");
+      else if (res)
+        {
+          /* at least one event available, handle them */
+          linuxaio_parse_events (EV_A_ ioev, res);
+
+          if (ecb_expect_true (ringbuf_valid))
+            {
+              /* if we have a ring buffer, handle any remaining events in it */
+              linuxaio_get_events_from_ring (EV_A);
+
+              /* at this point, we should have handled all outstanding events */
+              break;
+            }
+          else if (res < want)
+            /* otherwise, if there were fewere events than we wanted, we assume there are no more */
+            break;
+        }
+      else
+        break; /* no events from the kernel, we are done */
+
+      timeout = EV_TS_CONST (0.); /* only wait in the first iteration */
+    }
+}
+
+inline_size
+int
+linuxaio_io_setup (EV_P)
+{
+  linuxaio_ctx = 0;
+  return evsys_io_setup (linuxaio_nr_events (EV_A), &linuxaio_ctx);
+}
+
+static void
+linuxaio_poll (EV_P_ ev_tstamp timeout)
+{
+  int submitted;
+
+  /* first phase: submit new iocbs */
+
+  /* io_submit might return less than the requested number of iocbs */
+  /* this is, afaics, only because of errors, but we go by the book and use a loop, */
+  /* which allows us to pinpoint the erroneous iocb */
+  for (submitted = 0; submitted < linuxaio_submitcnt; )
+    {
+      int res = evsys_io_submit (linuxaio_ctx, linuxaio_submitcnt - submitted, linuxaio_submits + submitted);
+
+      if (ecb_expect_false (res < 0))
+        if (errno == EINVAL)
+          {
+            /* This happens for unsupported fds, officially, but in my testing,
+             * also randomly happens for supported fds. We fall back to good old
+             * poll() here, under the assumption that this is a very rare case.
+             * See https://lore.kernel.org/patchwork/patch/1047453/ to see
+             * discussion about such a case (ttys) where polling for POLLIN
+             * fails but POLLIN|POLLOUT works.
+             */
+            struct iocb *iocb = linuxaio_submits [submitted];
+            epoll_modify (EV_A_ iocb->aio_fildes, 0, anfds [iocb->aio_fildes].events);
+            iocb->aio_reqprio = -1; /* mark iocb as epoll */
+
+            res = 1; /* skip this iocb - another iocb, another chance */
+          }
+        else if (errno == EAGAIN)
+          {
+            /* This happens when the ring buffer is full, or some other shit we
+             * don't know and isn't documented. Most likely because we have too
+             * many requests and linux aio can't be assed to handle them.
+             * In this case, we try to allocate a larger ring buffer, freeing
+             * ours first. This might fail, in which case we have to fall back to 100%
+             * epoll.
+             * God, how I hate linux not getting its act together. Ever.
+             */
+            evsys_io_destroy (linuxaio_ctx);
+            linuxaio_submitcnt = 0;
+
+            /* rearm all fds with active iocbs */
+            {
+              int fd;
+	      for (fd = 0; fd < linuxaio_iocbpmax; ++fd)
+                if (linuxaio_iocbps [fd]->io.aio_buf)
+                  linuxaio_fd_rearm (EV_A_ fd);
+            }
+
+            ++linuxaio_iteration;
+            if (linuxaio_io_setup (EV_A) < 0)
+              {
+                /* TODO: rearm all and recreate epoll backend from scratch */
+                /* TODO: might be more prudent? */
+
+                /* to bad, we can't get a new aio context, go 100% epoll */
+                linuxaio_free_iocbp (EV_A);
+                ev_io_stop (EV_A_ &linuxaio_epoll_w);
+                ev_ref (EV_A);
+                linuxaio_ctx = 0;
+
+                backend        = EVBACKEND_EPOLL;
+                backend_modify = epoll_modify;
+                backend_poll   = epoll_poll;
+              }
+
+            timeout = EV_TS_CONST (0.);
+            /* it's easiest to handle this mess in another iteration */
+            return;
+          }
+        else if (errno == EBADF)
+          {
+            assert (("libev: event loop rejected bad fd", errno != EBADF));
+            fd_kill (EV_A_ linuxaio_submits [submitted]->aio_fildes);
+
+            res = 1; /* skip this iocb */
+          }
+        else if (errno == EINTR) /* not seen in reality, not documented */
+          res = 0; /* silently ignore and retry */
+        else
+          {
+            ev_syserr ("(libev) linuxaio io_submit");
+            res = 0;
+          }
+
+      submitted += res;
+    }
+
+  linuxaio_submitcnt = 0;
+
+  /* second phase: fetch and parse events */
+
+  linuxaio_get_events (EV_A_ timeout);
+}
+
+inline_size
+int
+linuxaio_init (EV_P_ int flags)
+{
+  /* would be great to have a nice test for IOCB_CMD_POLL instead */
+  /* also: test some semi-common fd types, such as files and ttys in recommended_backends */
+  /* 4.18 introduced IOCB_CMD_POLL, 4.19 made epoll work, and we need that */
+  if (ev_linux_version () < 0x041300)
+    return 0;
+
+  if (!epoll_init (EV_A_ 0))
+    return 0;
+
+  linuxaio_iteration = 0;
+
+  if (linuxaio_io_setup (EV_A) < 0)
+    {
+      epoll_destroy (EV_A);
+      return 0;
+    }
+
+  ev_io_init  (&linuxaio_epoll_w, linuxaio_epoll_cb, backend_fd, EV_READ);
+  ev_set_priority (&linuxaio_epoll_w, EV_MAXPRI);
+  ev_io_start (EV_A_ &linuxaio_epoll_w);
+  ev_unref (EV_A); /* watcher should not keep loop alive */
+
+  backend_modify = linuxaio_modify;
+  backend_poll   = linuxaio_poll;
+
+  linuxaio_iocbpmax = 0;
+  linuxaio_iocbps = 0;
+
+  linuxaio_submits = 0;
+  linuxaio_submitmax = 0;
+  linuxaio_submitcnt = 0;
+
+  return EVBACKEND_LINUXAIO;
+}
+
+inline_size
+void
+linuxaio_destroy (EV_P)
+{
+  epoll_destroy (EV_A);
+  linuxaio_free_iocbp (EV_A);
+  evsys_io_destroy (linuxaio_ctx); /* fails in child, aio context is destroyed */
+}
+
+ecb_cold
+static void
+linuxaio_fork (EV_P)
+{
+  linuxaio_submitcnt = 0; /* all pointers were invalidated */
+  linuxaio_free_iocbp (EV_A); /* this frees all iocbs, which is very heavy-handed */
+  evsys_io_destroy (linuxaio_ctx); /* fails in child, aio context is destroyed */
+
+  linuxaio_iteration = 0; /* we start over in the child */
+
+  while (linuxaio_io_setup (EV_A) < 0)
+    ev_syserr ("(libev) linuxaio io_setup");
+
+  /* forking epoll should also effectively unregister all fds from the backend */
+  epoll_fork (EV_A);
+  /* epoll_fork already did this. hopefully */
+  /*fd_rearm_all (EV_A);*/
+
+  ev_io_stop  (EV_A_ &linuxaio_epoll_w);
+  ev_io_set   (EV_A_ &linuxaio_epoll_w, backend_fd, EV_READ);
+  ev_io_start (EV_A_ &linuxaio_epoll_w);
+}
+
diff --git a/contrib/libev/ev_poll.c b/contrib/libev/ev_poll.c
index bd742b07f..e5508ddb0 100644
--- a/contrib/libev/ev_poll.c
+++ b/contrib/libev/ev_poll.c
@@ -1,7 +1,7 @@
 /*
  * libev poll fd activity backend
  *
- * Copyright (c) 2007,2008,2009,2010,2011 Marc Alexander Lehmann <libev@schmorp.de>
+ * Copyright (c) 2007,2008,2009,2010,2011,2016,2019 Marc Alexander Lehmann <libev@schmorp.de>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without modifica-
@@ -41,10 +41,12 @@
 
 inline_size
 void
-pollidx_init (int *base, int count)
+array_needsize_pollidx (int *base, int offset, int count)
 {
-  /* consider using memset (.., -1, ...), which is practically guaranteed
-   * to work on all systems implementing poll */
+  /* using memset (.., -1, ...) is tempting, we we try
+   * to be ultraportable
+   */
+  base += offset;
   while (count--)
     *base++ = -1;
 }
@@ -57,14 +59,14 @@ poll_modify (EV_P_ int fd, int oev, int nev)
   if (oev == nev)
     return;
 
-  array_needsize (int, pollidxs, pollidxmax, fd + 1, pollidx_init);
+  array_needsize (int, pollidxs, pollidxmax, fd + 1, array_needsize_pollidx);
 
   idx = pollidxs [fd];
 
   if (idx < 0) /* need to allocate a new pollfd */
     {
       pollidxs [fd] = idx = pollcnt++;
-      array_needsize (struct pollfd, polls, pollmax, pollcnt, EMPTY2);
+      array_needsize (struct pollfd, polls, pollmax, pollcnt, array_needsize_noinit);
       polls [idx].fd = fd;
     }
 
@@ -78,7 +80,7 @@ poll_modify (EV_P_ int fd, int oev, int nev)
     {
       pollidxs [fd] = -1;
 
-      if (expect_true (idx < --pollcnt))
+      if (ecb_expect_true (idx < --pollcnt))
         {
           polls [idx] = polls [pollcnt];
           pollidxs [polls [idx].fd] = idx;
@@ -93,10 +95,10 @@ poll_poll (EV_P_ ev_tstamp timeout)
   int res;
   
   EV_RELEASE_CB;
-  res = poll (polls, pollcnt, timeout * 1e3);
+  res = poll (polls, pollcnt, EV_TS_TO_MSEC (timeout));
   EV_ACQUIRE_CB;
 
-  if (expect_false (res < 0))
+  if (ecb_expect_false (res < 0))
     {
       if (errno == EBADF)
         fd_ebadf (EV_A);
@@ -108,14 +110,17 @@ poll_poll (EV_P_ ev_tstamp timeout)
   else
     for (p = polls; res; ++p)
       {
-        assert (("libev: poll() returned illegal result, broken BSD kernel?", p < polls + pollcnt));
+        assert (("libev: poll returned illegal result, broken BSD kernel?", p < polls + pollcnt));
 
-        if (expect_false (p->revents)) /* this expect is debatable */
+        if (ecb_expect_false (p->revents)) /* this expect is debatable */
           {
             --res;
 
-            if (expect_false (p->revents & POLLNVAL))
-              fd_kill (EV_A_ p->fd);
+            if (ecb_expect_false (p->revents & POLLNVAL))
+              {
+                assert (("libev: poll found invalid fd in poll set", 0));
+                fd_kill (EV_A_ p->fd);
+              }
             else
               fd_event (
                 EV_A_
@@ -131,7 +136,7 @@ inline_size
 int
 poll_init (EV_P_ int flags)
 {
-  backend_mintime = 1e-3;
+  backend_mintime = EV_TS_CONST (1e-3);
   backend_modify  = poll_modify;
   backend_poll    = poll_poll;
 
diff --git a/contrib/libev/ev_port.c b/contrib/libev/ev_port.c
index c7b0b70c1..f4cd9d99c 100644
--- a/contrib/libev/ev_port.c
+++ b/contrib/libev/ev_port.c
@@ -1,7 +1,7 @@
 /*
  * libev solaris event port backend
  *
- * Copyright (c) 2007,2008,2009,2010,2011 Marc Alexander Lehmann <libev@schmorp.de>
+ * Copyright (c) 2007,2008,2009,2010,2011,2019 Marc Alexander Lehmann <libev@schmorp.de>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without modifica-
@@ -69,7 +69,10 @@ port_associate_and_check (EV_P_ int fd, int ev)
   )
     {
       if (errno == EBADFD)
-        fd_kill (EV_A_ fd);
+        {
+          assert (("libev: port_associate found invalid fd", errno != EBADFD));
+          fd_kill (EV_A_ fd);
+        }
       else
         ev_syserr ("(libev) port_associate");
     }
@@ -129,7 +132,7 @@ port_poll (EV_P_ ev_tstamp timeout)
         }
     }
 
-  if (expect_false (nget == port_eventmax))
+  if (ecb_expect_false (nget == port_eventmax))
     {
       ev_free (port_events);
       port_eventmax = array_nextsize (sizeof (port_event_t), port_eventmax, port_eventmax + 1);
@@ -151,11 +154,11 @@ port_init (EV_P_ int flags)
 
   /* if my reading of the opensolaris kernel sources are correct, then
    * opensolaris does something very stupid: it checks if the time has already
-   * elapsed and doesn't round up if that is the case,m otherwise it DOES round
+   * elapsed and doesn't round up if that is the case, otherwise it DOES round
    * up. Since we can't know what the case is, we need to guess by using a
    * "large enough" timeout. Normally, 1e-9 would be correct.
    */
-  backend_mintime = 1e-3; /* needed to compensate for port_getn returning early */
+  backend_mintime = EV_TS_CONST (1e-3); /* needed to compensate for port_getn returning early */
   backend_modify  = port_modify;
   backend_poll    = port_poll;
 
diff --git a/contrib/libev/ev_select.c b/contrib/libev/ev_select.c
index ed1fc7ad9..b862c8113 100644
--- a/contrib/libev/ev_select.c
+++ b/contrib/libev/ev_select.c
@@ -108,7 +108,7 @@ select_modify (EV_P_ int fd, int oev, int nev)
     int     word = fd / NFDBITS;
     fd_mask mask = 1UL << (fd % NFDBITS);
 
-    if (expect_false (vec_max <= word))
+    if (ecb_expect_false (vec_max <= word))
       {
         int new_max = word + 1;
 
@@ -171,7 +171,7 @@ select_poll (EV_P_ ev_tstamp timeout)
 #endif
   EV_ACQUIRE_CB;
 
-  if (expect_false (res < 0))
+  if (ecb_expect_false (res < 0))
     {
       #if EV_SELECT_IS_WINSOCKET
       errno = WSAGetLastError ();
@@ -197,7 +197,7 @@ select_poll (EV_P_ ev_tstamp timeout)
         {
           if (timeout)
             {
-              unsigned long ms = timeout * 1e3;
+              unsigned long ms = EV_TS_TO_MSEC (timeout);
               Sleep (ms ? ms : 1);
             }
 
@@ -236,7 +236,7 @@ select_poll (EV_P_ ev_tstamp timeout)
           if (FD_ISSET (handle, (fd_set *)vec_eo)) events |= EV_WRITE;
           #endif
 
-          if (expect_true (events))
+          if (ecb_expect_true (events))
             fd_event (EV_A_ fd, events);
         }
   }
@@ -262,7 +262,7 @@ select_poll (EV_P_ ev_tstamp timeout)
               events |= word_r & mask ? EV_READ  : 0;
               events |= word_w & mask ? EV_WRITE : 0;
 
-              if (expect_true (events))
+              if (ecb_expect_true (events))
                 fd_event (EV_A_ word * NFDBITS + bit, events);
             }
       }
@@ -275,7 +275,7 @@ inline_size
 int
 select_init (EV_P_ int flags)
 {
-  backend_mintime = 1e-6;
+  backend_mintime = EV_TS_CONST (1e-6);
   backend_modify  = select_modify;
   backend_poll    = select_poll;
 
diff --git a/contrib/libev/ev_vars.h b/contrib/libev/ev_vars.h
index 30e9e285d..fb0c58316 100644
--- a/contrib/libev/ev_vars.h
+++ b/contrib/libev/ev_vars.h
@@ -1,7 +1,7 @@
 /*
  * loop member variable declarations
  *
- * Copyright (c) 2007,2008,2009,2010,2011,2012,2013 Marc Alexander Lehmann <libev@schmorp.de>
+ * Copyright (c) 2007,2008,2009,2010,2011,2012,2013,2019 Marc Alexander Lehmann <libev@schmorp.de>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without modifica-
@@ -107,6 +107,46 @@ VARx(int, epoll_epermcnt)
 VARx(int, epoll_epermmax)
 #endif
 
+#if EV_USE_LINUXAIO || EV_GENWRAP
+VARx(aio_context_t, linuxaio_ctx)
+VARx(int, linuxaio_iteration)
+VARx(struct aniocb **, linuxaio_iocbps)
+VARx(int, linuxaio_iocbpmax)
+VARx(struct iocb **, linuxaio_submits)
+VARx(int, linuxaio_submitcnt)
+VARx(int, linuxaio_submitmax)
+VARx(ev_io, linuxaio_epoll_w)
+#endif
+
+#if EV_USE_IOURING || EV_GENWRAP
+VARx(int, iouring_fd)
+VARx(unsigned, iouring_to_submit);
+VARx(int, iouring_entries)
+VARx(int, iouring_max_entries)
+VARx(void *, iouring_sq_ring)
+VARx(void *, iouring_cq_ring)
+VARx(void *, iouring_sqes)
+VARx(uint32_t, iouring_sq_ring_size)
+VARx(uint32_t, iouring_cq_ring_size)
+VARx(uint32_t, iouring_sqes_size)
+VARx(uint32_t, iouring_sq_head)
+VARx(uint32_t, iouring_sq_tail)
+VARx(uint32_t, iouring_sq_ring_mask)
+VARx(uint32_t, iouring_sq_ring_entries)
+VARx(uint32_t, iouring_sq_flags)
+VARx(uint32_t, iouring_sq_dropped)
+VARx(uint32_t, iouring_sq_array)
+VARx(uint32_t, iouring_cq_head)
+VARx(uint32_t, iouring_cq_tail)
+VARx(uint32_t, iouring_cq_ring_mask)
+VARx(uint32_t, iouring_cq_ring_entries)
+VARx(uint32_t, iouring_cq_overflow)
+VARx(uint32_t, iouring_cq_cqes)
+VARx(ev_tstamp, iouring_tfd_to)
+VARx(int, iouring_tfd)
+VARx(ev_io, iouring_tfd_w)
+#endif
+
 #if EV_USE_KQUEUE || EV_GENWRAP
 VARx(pid_t, kqueue_fd_pid)
 VARx(struct kevent *, kqueue_changes)
@@ -187,6 +227,11 @@ VARx(ev_io, sigfd_w)
 VARx(sigset_t, sigfd_set)
 #endif
 
+#if EV_USE_TIMERFD || EV_GENWRAP
+VARx(int, timerfd) /* timerfd for time jump detection */
+VARx(ev_io, timerfd_w)
+#endif
+
 VARx(unsigned int, origflags) /* original loop flags */
 
 #if EV_FEATURE_API || EV_GENWRAP
diff --git a/contrib/libev/ev_win32.c b/contrib/libev/ev_win32.c
index fd671356a..97344c3e1 100644
--- a/contrib/libev/ev_win32.c
+++ b/contrib/libev/ev_win32.c
@@ -154,8 +154,8 @@ ev_time (void)
   ui.u.LowPart  = ft.dwLowDateTime;
   ui.u.HighPart = ft.dwHighDateTime;
 
-  /* msvc cannot convert ulonglong to double... yes, it is that sucky */
-  return (LONGLONG)(ui.QuadPart - 116444736000000000) * 1e-7;
+  /* also, msvc cannot convert ulonglong to double... yes, it is that sucky */
+  return EV_TS_FROM_USEC (((LONGLONG)(ui.QuadPart - 116444736000000000) * 1e-1));
 }
 
 #endif
diff --git a/contrib/libev/ev_wrap.h b/contrib/libev/ev_wrap.h
index ad989ea7d..45d793ced 100644
--- a/contrib/libev/ev_wrap.h
+++ b/contrib/libev/ev_wrap.h
@@ -44,12 +44,46 @@
 #define invoke_cb ((loop)->invoke_cb)
 #define io_blocktime ((loop)->io_blocktime)
 #define iocp ((loop)->iocp)
+#define iouring_cq_cqes ((loop)->iouring_cq_cqes)
+#define iouring_cq_head ((loop)->iouring_cq_head)
+#define iouring_cq_overflow ((loop)->iouring_cq_overflow)
+#define iouring_cq_ring ((loop)->iouring_cq_ring)
+#define iouring_cq_ring_entries ((loop)->iouring_cq_ring_entries)
+#define iouring_cq_ring_mask ((loop)->iouring_cq_ring_mask)
+#define iouring_cq_ring_size ((loop)->iouring_cq_ring_size)
+#define iouring_cq_tail ((loop)->iouring_cq_tail)
+#define iouring_entries ((loop)->iouring_entries)
+#define iouring_fd ((loop)->iouring_fd)
+#define iouring_max_entries ((loop)->iouring_max_entries)
+#define iouring_sq_array ((loop)->iouring_sq_array)
+#define iouring_sq_dropped ((loop)->iouring_sq_dropped)
+#define iouring_sq_flags ((loop)->iouring_sq_flags)
+#define iouring_sq_head ((loop)->iouring_sq_head)
+#define iouring_sq_ring ((loop)->iouring_sq_ring)
+#define iouring_sq_ring_entries ((loop)->iouring_sq_ring_entries)
+#define iouring_sq_ring_mask ((loop)->iouring_sq_ring_mask)
+#define iouring_sq_ring_size ((loop)->iouring_sq_ring_size)
+#define iouring_sq_tail ((loop)->iouring_sq_tail)
+#define iouring_sqes ((loop)->iouring_sqes)
+#define iouring_sqes_size ((loop)->iouring_sqes_size)
+#define iouring_tfd ((loop)->iouring_tfd)
+#define iouring_tfd_to ((loop)->iouring_tfd_to)
+#define iouring_tfd_w ((loop)->iouring_tfd_w)
+#define iouring_to_submit ((loop)->iouring_to_submit)
 #define kqueue_changecnt ((loop)->kqueue_changecnt)
 #define kqueue_changemax ((loop)->kqueue_changemax)
 #define kqueue_changes ((loop)->kqueue_changes)
 #define kqueue_eventmax ((loop)->kqueue_eventmax)
 #define kqueue_events ((loop)->kqueue_events)
 #define kqueue_fd_pid ((loop)->kqueue_fd_pid)
+#define linuxaio_ctx ((loop)->linuxaio_ctx)
+#define linuxaio_epoll_w ((loop)->linuxaio_epoll_w)
+#define linuxaio_iocbpmax ((loop)->linuxaio_iocbpmax)
+#define linuxaio_iocbps ((loop)->linuxaio_iocbps)
+#define linuxaio_iteration ((loop)->linuxaio_iteration)
+#define linuxaio_submitcnt ((loop)->linuxaio_submitcnt)
+#define linuxaio_submitmax ((loop)->linuxaio_submitmax)
+#define linuxaio_submits ((loop)->linuxaio_submits)
 #define loop_count ((loop)->loop_count)
 #define loop_depth ((loop)->loop_depth)
 #define loop_done ((loop)->loop_done)
@@ -89,6 +123,8 @@
 #define sigfd_w ((loop)->sigfd_w)
 #define timeout_blocktime ((loop)->timeout_blocktime)
 #define timercnt ((loop)->timercnt)
+#define timerfd ((loop)->timerfd)
+#define timerfd_w ((loop)->timerfd_w)
 #define timermax ((loop)->timermax)
 #define timers ((loop)->timers)
 #define userdata ((loop)->userdata)
@@ -143,12 +179,46 @@
 #undef invoke_cb
 #undef io_blocktime
 #undef iocp
+#undef iouring_cq_cqes
+#undef iouring_cq_head
+#undef iouring_cq_overflow
+#undef iouring_cq_ring
+#undef iouring_cq_ring_entries
+#undef iouring_cq_ring_mask
+#undef iouring_cq_ring_size
+#undef iouring_cq_tail
+#undef iouring_entries
+#undef iouring_fd
+#undef iouring_max_entries
+#undef iouring_sq_array
+#undef iouring_sq_dropped
+#undef iouring_sq_flags
+#undef iouring_sq_head
+#undef iouring_sq_ring
+#undef iouring_sq_ring_entries
+#undef iouring_sq_ring_mask
+#undef iouring_sq_ring_size
+#undef iouring_sq_tail
+#undef iouring_sqes
+#undef iouring_sqes_size
+#undef iouring_tfd
+#undef iouring_tfd_to
+#undef iouring_tfd_w
+#undef iouring_to_submit
 #undef kqueue_changecnt
 #undef kqueue_changemax
 #undef kqueue_changes
 #undef kqueue_eventmax
 #undef kqueue_events
 #undef kqueue_fd_pid
+#undef linuxaio_ctx
+#undef linuxaio_epoll_w
+#undef linuxaio_iocbpmax
+#undef linuxaio_iocbps
+#undef linuxaio_iteration
+#undef linuxaio_submitcnt
+#undef linuxaio_submitmax
+#undef linuxaio_submits
 #undef loop_count
 #undef loop_depth
 #undef loop_done
@@ -188,6 +258,8 @@
 #undef sigfd_w
 #undef timeout_blocktime
 #undef timercnt
+#undef timerfd
+#undef timerfd_w
 #undef timermax
 #undef timers
 #undef userdata
diff --git a/src/libserver/cfg_utils.c b/src/libserver/cfg_utils.c
index 7a5da9807..7e04adb97 100644
--- a/src/libserver/cfg_utils.c
+++ b/src/libserver/cfg_utils.c
@@ -2631,6 +2631,14 @@ rspamd_config_ev_backend_to_string (int ev_backend, gboolean *effective)
 	}
 
 	if (ev_backend & EVBACKEND_EPOLL) {
+		if (ev_backend & EVBACKEND_IOURING) {
+			SET_EFFECTIVE (TRUE);
+			return "epoll+io_uring";
+		}
+		if (ev_backend & EVBACKEND_LINUXAIO) {
+			SET_EFFECTIVE (TRUE);
+			return "epoll+aio";
+		}
 		SET_EFFECTIVE (TRUE);
 		return "epoll";
 	}