Add Goroutine stack inspector to admin/monitor (#19207)

Continues on from #19202.

Following the addition of pprof labels we can now more easily understand the relationship between a goroutine and the requests that spawn them. 

This PR takes advantage of the labels and adds a few others, then provides a mechanism for the monitoring page to query the pprof goroutine profile.

The binary profile that results from this profile is immediately piped in to the google library for parsing this and then stack traces are formed for the goroutines.

If the goroutine is within a context or has been created from a goroutine within a process context it will acquire the process description labels for that process. 

The goroutines are mapped with there associate pids and any that do not have an associated pid are placed in a group at the bottom as unbound.

In this way we should be able to more easily examine goroutines that have been stuck.

A manager command `gitea manager processes` is also provided that can export the processes (with or without stacktraces) to the command line.

Signed-off-by: Andrew Thornton <art27@cantab.net>

6 files changed, 551 insertions, 207 deletions

diff --git a/modules/process/error.go b/modules/process/error.go
new file mode 100644
index 0000000000..7a72bda40e
--- /dev/null
+++ b/modules/process/error.go
@@ -0,0 +1,26 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package process
+
+import "fmt"
+
+// Error is a wrapped error describing the error results of Process Execution
+type Error struct {
+	PID         IDType
+	Description string
+	Err         error
+	CtxErr      error
+	Stdout      string
+	Stderr      string
+}
+
+func (err *Error) Error() string {
+	return fmt.Sprintf("exec(%s:%s) failed: %v(%v) stdout: %s stderr: %s", err.PID, err.Description, err.Err, err.CtxErr, err.Stdout, err.Stderr)
+}
+
+// Unwrap implements the unwrappable implicit interface for go1.13 Unwrap()
+func (err *Error) Unwrap() error {
+	return err.Err
+}
diff --git a/modules/process/manager.go b/modules/process/manager.go
index 26dd6d535f..5d7aee760f 100644
--- a/modules/process/manager.go
+++ b/modules/process/manager.go
@@ -6,13 +6,8 @@
 package process
 
 import (
-	"bytes"
 	"context"
-	"fmt"
-	"io"
-	"os/exec"
 	"runtime/pprof"
-	"sort"
 	"strconv"
 	"sync"
 	"time"
@@ -30,6 +25,18 @@ var (
 	DefaultContext = context.Background()
 )
 
+// DescriptionPProfLabel is a label set on goroutines that have a process attached
+const DescriptionPProfLabel = "process-description"
+
+// PIDPProfLabel is a label set on goroutines that have a process attached
+const PIDPProfLabel = "pid"
+
+// PPIDPProfLabel is a label set on goroutines that have a process attached
+const PPIDPProfLabel = "ppid"
+
+// ProcessTypePProfLabel is a label set on goroutines that have a process attached
+const ProcessTypePProfLabel = "process-type"
+
 // IDType is a pid type
 type IDType string
 
@@ -44,15 +51,15 @@ type Manager struct {
 	next     int64
 	lastTime int64
 
-	processes map[IDType]*Process
+	processMap map[IDType]*process
 }
 
 // GetManager returns a Manager and initializes one as singleton if there's none yet
 func GetManager() *Manager {
 	managerInit.Do(func() {
 		manager = &Manager{
-			processes: make(map[IDType]*Process),
-			next:      1,
+			processMap: make(map[IDType]*process),
+			next:       1,
 		}
 	})
 	return manager
@@ -69,12 +76,25 @@ func GetManager() *Manager {
 func (pm *Manager) AddContext(parent context.Context, description string) (ctx context.Context, cancel context.CancelFunc, finished FinishedFunc) {
 	ctx, cancel = context.WithCancel(parent)
 
-	ctx, pid, finished := pm.Add(ctx, description, cancel)
+	ctx, _, finished = pm.Add(ctx, description, cancel, NormalProcessType, true)
 
-	return &Context{
-		Context: ctx,
-		pid:     pid,
-	}, cancel, finished
+	return ctx, cancel, finished
+}
+
+// AddTypedContext creates a new context and adds it as a process. Once the process is finished, finished must be called
+// to remove the process from the process table. It should not be called until the process is finished but must always be called.
+//
+// cancel should be used to cancel the returned context, however it will not remove the process from the process table.
+// finished will cancel the returned context and remove it from the process table.
+//
+// Most processes will not need to use the cancel function but there will be cases whereby you want to cancel the process but not immediately remove it from the
+// process table.
+func (pm *Manager) AddTypedContext(parent context.Context, description, processType string, currentlyRunning bool) (ctx context.Context, cancel context.CancelFunc, finished FinishedFunc) {
+	ctx, cancel = context.WithCancel(parent)
+
+	ctx, _, finished = pm.Add(ctx, description, cancel, processType, currentlyRunning)
+
+	return ctx, cancel, finished
 }
 
 // AddContextTimeout creates a new context and add it as a process. Once the process is finished, finished must be called
@@ -90,52 +110,61 @@ func (pm *Manager) AddContextTimeout(parent context.Context, timeout time.Durati
 		// it's meaningless to use timeout <= 0, and it must be a bug! so we must panic here to tell developers to make the timeout correct
 		panic("the timeout must be greater than zero, otherwise the context will be cancelled immediately")
 	}
+
 	ctx, cancel = context.WithTimeout(parent, timeout)
 
-	ctx, pid, finshed := pm.Add(ctx, description, cancel)
+	ctx, _, finshed = pm.Add(ctx, description, cancel, NormalProcessType, true)
 
-	return &Context{
-		Context: ctx,
-		pid:     pid,
-	}, cancel, finshed
+	return ctx, cancel, finshed
 }
 
 // Add create a new process
-func (pm *Manager) Add(ctx context.Context, description string, cancel context.CancelFunc) (context.Context, IDType, FinishedFunc) {
+func (pm *Manager) Add(ctx context.Context, description string, cancel context.CancelFunc, processType string, currentlyRunning bool) (context.Context, IDType, FinishedFunc) {
 	parentPID := GetParentPID(ctx)
 
 	pm.mutex.Lock()
 	start, pid := pm.nextPID()
 
-	parent := pm.processes[parentPID]
+	parent := pm.processMap[parentPID]
 	if parent == nil {
 		parentPID = ""
 	}
 
-	process := &Process{
+	process := &process{
 		PID:         pid,
 		ParentPID:   parentPID,
 		Description: description,
 		Start:       start,
 		Cancel:      cancel,
+		Type:        processType,
 	}
 
-	finished := func() {
-		cancel()
-		pm.remove(process)
-		pprof.SetGoroutineLabels(ctx)
+	var finished FinishedFunc
+	if currentlyRunning {
+		finished = func() {
+			cancel()
+			pm.remove(process)
+			pprof.SetGoroutineLabels(ctx)
+		}
+	} else {
+		finished = func() {
+			cancel()
+			pm.remove(process)
+		}
 	}
 
-	if parent != nil {
-		parent.AddChild(process)
-	}
-	pm.processes[pid] = process
+	pm.processMap[pid] = process
 	pm.mutex.Unlock()
 
-	pprofCtx := pprof.WithLabels(ctx, pprof.Labels("process-description", description, "ppid", string(parentPID), "pid", string(pid)))
-	pprof.SetGoroutineLabels(pprofCtx)
+	pprofCtx := pprof.WithLabels(ctx, pprof.Labels(DescriptionPProfLabel, description, PPIDPProfLabel, string(parentPID), PIDPProfLabel, string(pid), ProcessTypePProfLabel, processType))
+	if currentlyRunning {
+		pprof.SetGoroutineLabels(pprofCtx)
+	}
 
-	return pprofCtx, pid, finished
+	return &Context{
+		Context: pprofCtx,
+		pid:     pid,
+	}, pid, finished
 }
 
 // nextPID will return the next available PID. pm.mutex should already be locked.
@@ -160,142 +189,24 @@ func (pm *Manager) nextPID() (start time.Time, pid IDType) {
 // Remove a process from the ProcessManager.
 func (pm *Manager) Remove(pid IDType) {
 	pm.mutex.Lock()
-	delete(pm.processes, pid)
+	delete(pm.processMap, pid)
 	pm.mutex.Unlock()
 }
 
-func (pm *Manager) remove(process *Process) {
+func (pm *Manager) remove(process *process) {
 	pm.mutex.Lock()
-	if p := pm.processes[process.PID]; p == process {
-		delete(pm.processes, process.PID)
+	defer pm.mutex.Unlock()
+	if p := pm.processMap[process.PID]; p == process {
+		delete(pm.processMap, process.PID)
 	}
-	parent := pm.processes[process.ParentPID]
-	pm.mutex.Unlock()
-
-	if parent == nil {
-		return
-	}
-
-	parent.RemoveChild(process)
 }
 
 // Cancel a process in the ProcessManager.
 func (pm *Manager) Cancel(pid IDType) {
 	pm.mutex.Lock()
-	process, ok := pm.processes[pid]
+	process, ok := pm.processMap[pid]
 	pm.mutex.Unlock()
-	if ok {
+	if ok && process.Type != SystemProcessType {
 		process.Cancel()
 	}
 }
-
-// Processes gets the processes in a thread safe manner
-func (pm *Manager) Processes(onlyRoots bool) []*Process {
-	pm.mutex.Lock()
-	processes := make([]*Process, 0, len(pm.processes))
-	if onlyRoots {
-		for _, process := range pm.processes {
-			if _, has := pm.processes[process.ParentPID]; !has {
-				processes = append(processes, process)
-			}
-		}
-	} else {
-		for _, process := range pm.processes {
-			processes = append(processes, process)
-		}
-	}
-	pm.mutex.Unlock()
-
-	sort.Slice(processes, func(i, j int) bool {
-		left, right := processes[i], processes[j]
-
-		return left.Start.Before(right.Start)
-	})
-
-	return processes
-}
-
-// Exec a command and use the default timeout.
-func (pm *Manager) Exec(desc, cmdName string, args ...string) (string, string, error) {
-	return pm.ExecDir(DefaultContext, -1, "", desc, cmdName, args...)
-}
-
-// ExecTimeout a command and use a specific timeout duration.
-func (pm *Manager) ExecTimeout(timeout time.Duration, desc, cmdName string, args ...string) (string, string, error) {
-	return pm.ExecDir(DefaultContext, timeout, "", desc, cmdName, args...)
-}
-
-// ExecDir a command and use the default timeout.
-func (pm *Manager) ExecDir(ctx context.Context, timeout time.Duration, dir, desc, cmdName string, args ...string) (string, string, error) {
-	return pm.ExecDirEnv(ctx, timeout, dir, desc, nil, cmdName, args...)
-}
-
-// ExecDirEnv runs a command in given path and environment variables, and waits for its completion
-// up to the given timeout (or DefaultTimeout if -1 is given).
-// Returns its complete stdout and stderr
-// outputs and an error, if any (including timeout)
-func (pm *Manager) ExecDirEnv(ctx context.Context, timeout time.Duration, dir, desc string, env []string, cmdName string, args ...string) (string, string, error) {
-	return pm.ExecDirEnvStdIn(ctx, timeout, dir, desc, env, nil, cmdName, args...)
-}
-
-// ExecDirEnvStdIn runs a command in given path and environment variables with provided stdIN, and waits for its completion
-// up to the given timeout (or DefaultTimeout if -1 is given).
-// Returns its complete stdout and stderr
-// outputs and an error, if any (including timeout)
-func (pm *Manager) ExecDirEnvStdIn(ctx context.Context, timeout time.Duration, dir, desc string, env []string, stdIn io.Reader, cmdName string, args ...string) (string, string, error) {
-	if timeout <= 0 {
-		timeout = 60 * time.Second
-	}
-
-	stdOut := new(bytes.Buffer)
-	stdErr := new(bytes.Buffer)
-
-	ctx, _, finished := pm.AddContextTimeout(ctx, timeout, desc)
-	defer finished()
-
-	cmd := exec.CommandContext(ctx, cmdName, args...)
-	cmd.Dir = dir
-	cmd.Env = env
-	cmd.Stdout = stdOut
-	cmd.Stderr = stdErr
-	if stdIn != nil {
-		cmd.Stdin = stdIn
-	}
-
-	if err := cmd.Start(); err != nil {
-		return "", "", err
-	}
-
-	err := cmd.Wait()
-	if err != nil {
-		err = &Error{
-			PID:         GetPID(ctx),
-			Description: desc,
-			Err:         err,
-			CtxErr:      ctx.Err(),
-			Stdout:      stdOut.String(),
-			Stderr:      stdErr.String(),
-		}
-	}
-
-	return stdOut.String(), stdErr.String(), err
-}
-
-// Error is a wrapped error describing the error results of Process Execution
-type Error struct {
-	PID         IDType
-	Description string
-	Err         error
-	CtxErr      error
-	Stdout      string
-	Stderr      string
-}
-
-func (err *Error) Error() string {
-	return fmt.Sprintf("exec(%s:%s) failed: %v(%v) stdout: %s stderr: %s", err.PID, err.Description, err.Err, err.CtxErr, err.Stdout, err.Stderr)
-}
-
-// Unwrap implements the unwrappable implicit interface for go1.13 Unwrap()
-func (err *Error) Unwrap() error {
-	return err.Err
-}
diff --git a/modules/process/manager_exec.go b/modules/process/manager_exec.go
new file mode 100644
index 0000000000..61ddae646f
--- /dev/null
+++ b/modules/process/manager_exec.go
@@ -0,0 +1,79 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package process
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"os/exec"
+	"time"
+)
+
+// Exec a command and use the default timeout.
+func (pm *Manager) Exec(desc, cmdName string, args ...string) (string, string, error) {
+	return pm.ExecDir(DefaultContext, -1, "", desc, cmdName, args...)
+}
+
+// ExecTimeout a command and use a specific timeout duration.
+func (pm *Manager) ExecTimeout(timeout time.Duration, desc, cmdName string, args ...string) (string, string, error) {
+	return pm.ExecDir(DefaultContext, timeout, "", desc, cmdName, args...)
+}
+
+// ExecDir a command and use the default timeout.
+func (pm *Manager) ExecDir(ctx context.Context, timeout time.Duration, dir, desc, cmdName string, args ...string) (string, string, error) {
+	return pm.ExecDirEnv(ctx, timeout, dir, desc, nil, cmdName, args...)
+}
+
+// ExecDirEnv runs a command in given path and environment variables, and waits for its completion
+// up to the given timeout (or DefaultTimeout if -1 is given).
+// Returns its complete stdout and stderr
+// outputs and an error, if any (including timeout)
+func (pm *Manager) ExecDirEnv(ctx context.Context, timeout time.Duration, dir, desc string, env []string, cmdName string, args ...string) (string, string, error) {
+	return pm.ExecDirEnvStdIn(ctx, timeout, dir, desc, env, nil, cmdName, args...)
+}
+
+// ExecDirEnvStdIn runs a command in given path and environment variables with provided stdIN, and waits for its completion
+// up to the given timeout (or DefaultTimeout if timeout <= 0 is given).
+// Returns its complete stdout and stderr
+// outputs and an error, if any (including timeout)
+func (pm *Manager) ExecDirEnvStdIn(ctx context.Context, timeout time.Duration, dir, desc string, env []string, stdIn io.Reader, cmdName string, args ...string) (string, string, error) {
+	if timeout <= 0 {
+		timeout = 60 * time.Second
+	}
+
+	stdOut := new(bytes.Buffer)
+	stdErr := new(bytes.Buffer)
+
+	ctx, _, finished := pm.AddContextTimeout(ctx, timeout, desc)
+	defer finished()
+
+	cmd := exec.CommandContext(ctx, cmdName, args...)
+	cmd.Dir = dir
+	cmd.Env = env
+	cmd.Stdout = stdOut
+	cmd.Stderr = stdErr
+	if stdIn != nil {
+		cmd.Stdin = stdIn
+	}
+
+	if err := cmd.Start(); err != nil {
+		return "", "", err
+	}
+
+	err := cmd.Wait()
+	if err != nil {
+		err = &Error{
+			PID:         GetPID(ctx),
+			Description: desc,
+			Err:         err,
+			CtxErr:      ctx.Err(),
+			Stdout:      stdOut.String(),
+			Stderr:      stdErr.String(),
+		}
+	}
+
+	return stdOut.String(), stdErr.String(), err
+}
diff --git a/modules/process/manager_stacktraces.go b/modules/process/manager_stacktraces.go
new file mode 100644
index 0000000000..fbe3374b87
--- /dev/null
+++ b/modules/process/manager_stacktraces.go
@@ -0,0 +1,355 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package process
+
+import (
+	"fmt"
+	"io"
+	"runtime/pprof"
+	"sort"
+	"time"
+
+	"github.com/google/pprof/profile"
+)
+
+// StackEntry is an entry on a stacktrace
+type StackEntry struct {
+	Function string
+	File     string
+	Line     int
+}
+
+// Label represents a pprof label assigned to goroutine stack
+type Label struct {
+	Name  string
+	Value string
+}
+
+// Stack is a stacktrace relating to a goroutine. (Multiple goroutines may have the same stacktrace)
+type Stack struct {
+	Count       int64 // Number of goroutines with this stack trace
+	Description string
+	Labels      []*Label      `json:",omitempty"`
+	Entry       []*StackEntry `json:",omitempty"`
+}
+
+// A Process is a combined representation of a Process and a Stacktrace for the goroutines associated with it
+type Process struct {
+	PID         IDType
+	ParentPID   IDType
+	Description string
+	Start       time.Time
+	Type        string
+
+	Children []*Process `json:",omitempty"`
+	Stacks   []*Stack   `json:",omitempty"`
+}
+
+// Processes gets the processes in a thread safe manner
+func (pm *Manager) Processes(flat, noSystem bool) ([]*Process, int) {
+	pm.mutex.Lock()
+	processCount := len(pm.processMap)
+	processes := make([]*Process, 0, len(pm.processMap))
+	if flat {
+		for _, process := range pm.processMap {
+			if noSystem && process.Type == SystemProcessType {
+				continue
+			}
+			processes = append(processes, process.toProcess())
+		}
+	} else {
+		// We need our own processMap
+		processMap := map[IDType]*Process{}
+		for _, internalProcess := range pm.processMap {
+			process, ok := processMap[internalProcess.PID]
+			if !ok {
+				process = internalProcess.toProcess()
+				processMap[process.PID] = process
+			}
+
+			// Check its parent
+			if process.ParentPID == "" {
+				processes = append(processes, process)
+				continue
+			}
+
+			internalParentProcess, ok := pm.processMap[internalProcess.ParentPID]
+			if ok {
+				parentProcess, ok := processMap[process.ParentPID]
+				if !ok {
+					parentProcess = internalParentProcess.toProcess()
+					processMap[parentProcess.PID] = parentProcess
+				}
+				parentProcess.Children = append(parentProcess.Children, process)
+				continue
+			}
+
+			processes = append(processes, process)
+		}
+	}
+	pm.mutex.Unlock()
+
+	if !flat && noSystem {
+		for i := 0; i < len(processes); i++ {
+			process := processes[i]
+			if process.Type != SystemProcessType {
+				continue
+			}
+			processes[len(processes)-1], processes[i] = processes[i], processes[len(processes)-1]
+			processes = append(processes[:len(processes)-1], process.Children...)
+			i--
+		}
+	}
+
+	// Sort by process' start time. Oldest process appears first.
+	sort.Slice(processes, func(i, j int) bool {
+		left, right := processes[i], processes[j]
+
+		return left.Start.Before(right.Start)
+	})
+
+	return processes, processCount
+}
+
+// ProcessStacktraces gets the processes and stacktraces in a thread safe manner
+func (pm *Manager) ProcessStacktraces(flat, noSystem bool) ([]*Process, int, int64, error) {
+	var stacks *profile.Profile
+	var err error
+
+	// We cannot use the pm.ProcessMap here because we will release the mutex ...
+	processMap := map[IDType]*Process{}
+	processCount := 0
+
+	// Lock the manager
+	pm.mutex.Lock()
+	processCount = len(pm.processMap)
+
+	// Add a defer to unlock in case there is a panic
+	unlocked := false
+	defer func() {
+		if !unlocked {
+			pm.mutex.Unlock()
+		}
+	}()
+
+	processes := make([]*Process, 0, len(pm.processMap))
+	if flat {
+		for _, internalProcess := range pm.processMap {
+			process := internalProcess.toProcess()
+			processMap[process.PID] = process
+			if noSystem && internalProcess.Type == SystemProcessType {
+				continue
+			}
+			processes = append(processes, process)
+		}
+	} else {
+		for _, internalProcess := range pm.processMap {
+			process, ok := processMap[internalProcess.PID]
+			if !ok {
+				process = internalProcess.toProcess()
+				processMap[process.PID] = process
+			}
+
+			// Check its parent
+			if process.ParentPID == "" {
+				processes = append(processes, process)
+				continue
+			}
+
+			internalParentProcess, ok := pm.processMap[internalProcess.ParentPID]
+			if ok {
+				parentProcess, ok := processMap[process.ParentPID]
+				if !ok {
+					parentProcess = internalParentProcess.toProcess()
+					processMap[parentProcess.PID] = parentProcess
+				}
+				parentProcess.Children = append(parentProcess.Children, process)
+				continue
+			}
+
+			processes = append(processes, process)
+		}
+	}
+
+	// Now from within the lock we need to get the goroutines.
+	// Why? If we release the lock then between between filling the above map and getting
+	// the stacktraces another process could be created which would then look like a dead process below
+	reader, writer := io.Pipe()
+	defer reader.Close()
+	go func() {
+		err := pprof.Lookup("goroutine").WriteTo(writer, 0)
+		_ = writer.CloseWithError(err)
+	}()
+	stacks, err = profile.Parse(reader)
+	if err != nil {
+		return nil, 0, 0, err
+	}
+
+	// Unlock the mutex
+	pm.mutex.Unlock()
+	unlocked = true
+
+	goroutineCount := int64(0)
+
+	// Now walk through the "Sample" slice in the goroutines stack
+	for _, sample := range stacks.Sample {
+		// In the "goroutine" pprof profile each sample represents one or more goroutines
+		// with the same labels and stacktraces.
+
+		// We will represent each goroutine by a `Stack`
+		stack := &Stack{}
+
+		// Add the non-process associated labels from the goroutine sample to the Stack
+		for name, value := range sample.Label {
+			if name == DescriptionPProfLabel || name == PIDPProfLabel || (!flat && name == PPIDPProfLabel) || name == ProcessTypePProfLabel {
+				continue
+			}
+
+			// Labels from the "goroutine" pprof profile only have one value.
+			// This is because the underlying representation is a map[string]string
+			if len(value) != 1 {
+				// Unexpected...
+				return nil, 0, 0, fmt.Errorf("label: %s in goroutine stack with unexpected number of values: %v", name, value)
+			}
+
+			stack.Labels = append(stack.Labels, &Label{Name: name, Value: value[0]})
+		}
+
+		// The number of goroutines that this sample represents is the `stack.Value[0]`
+		stack.Count = sample.Value[0]
+		goroutineCount += stack.Count
+
+		// Now we want to associate this Stack with a Process.
+		var process *Process
+
+		// Try to get the PID from the goroutine labels
+		if pidvalue, ok := sample.Label[PIDPProfLabel]; ok && len(pidvalue) == 1 {
+			pid := IDType(pidvalue[0])
+
+			// Now try to get the process from our map
+			process, ok = processMap[pid]
+			if !ok && pid != "" {
+				// This means that no process has been found in the process map - but there was a process PID
+				// Therefore this goroutine belongs to a dead process and it has escaped control of the process as it
+				// should have died with the process context cancellation.
+
+				// We need to create a dead process holder for this process and label it appropriately
+
+				// get the parent PID
+				ppid := IDType("")
+				if value, ok := sample.Label[PPIDPProfLabel]; ok && len(value) == 1 {
+					ppid = IDType(value[0])
+				}
+
+				// format the description
+				description := "(dead process)"
+				if value, ok := sample.Label[DescriptionPProfLabel]; ok && len(value) == 1 {
+					description = value[0] + " " + description
+				}
+
+				// override the type of the process to "code" but add the old type as a label on the first stack
+				ptype := NoneProcessType
+				if value, ok := sample.Label[ProcessTypePProfLabel]; ok && len(value) == 1 {
+					stack.Labels = append(stack.Labels, &Label{Name: ProcessTypePProfLabel, Value: value[0]})
+				}
+				process = &Process{
+					PID:         pid,
+					ParentPID:   ppid,
+					Description: description,
+					Type:        ptype,
+				}
+
+				// Now add the dead process back to the map and tree so we don't go back through this again.
+				processMap[process.PID] = process
+				added := false
+				if process.ParentPID != "" && !flat {
+					if parent, ok := processMap[process.ParentPID]; ok {
+						parent.Children = append(parent.Children, process)
+						added = true
+					}
+				}
+				if !added {
+					processes = append(processes, process)
+				}
+			}
+		}
+
+		if process == nil {
+			// This means that the sample we're looking has no PID label
+			var ok bool
+			process, ok = processMap[""]
+			if !ok {
+				// this is the first time we've come acrross an unassociated goroutine so create a "process" to hold them
+				process = &Process{
+					Description: "(unassociated)",
+					Type:        NoneProcessType,
+				}
+				processMap[process.PID] = process
+				processes = append(processes, process)
+			}
+		}
+
+		// The sample.Location represents a stack trace for this goroutine,
+		// however each Location can represent multiple lines (mostly due to inlining)
+		// so we need to walk the lines too
+		for _, location := range sample.Location {
+			for _, line := range location.Line {
+				entry := &StackEntry{
+					Function: line.Function.Name,
+					File:     line.Function.Filename,
+					Line:     int(line.Line),
+				}
+				stack.Entry = append(stack.Entry, entry)
+			}
+		}
+
+		// Now we need a short-descriptive name to call the stack trace if when it is folded and
+		// assuming the stack trace has some lines we'll choose the bottom of the stack (i.e. the
+		// initial function that started the stack trace.) The top of the stack is unlikely to
+		// be very helpful as a lot of the time it will be runtime.select or some other call into
+		// a std library.
+		stack.Description = "(unknown)"
+		if len(stack.Entry) > 0 {
+			stack.Description = stack.Entry[len(stack.Entry)-1].Function
+		}
+
+		process.Stacks = append(process.Stacks, stack)
+	}
+
+	// restrict to not show system processes
+	if noSystem {
+		for i := 0; i < len(processes); i++ {
+			process := processes[i]
+			if process.Type != SystemProcessType && process.Type != NoneProcessType {
+				continue
+			}
+			processes[len(processes)-1], processes[i] = processes[i], processes[len(processes)-1]
+			processes = append(processes[:len(processes)-1], process.Children...)
+			i--
+		}
+	}
+
+	// Now finally re-sort the processes. Newest process appears first
+	after := func(processes []*Process) func(i, j int) bool {
+		return func(i, j int) bool {
+			left, right := processes[i], processes[j]
+			return left.Start.After(right.Start)
+		}
+	}
+	sort.Slice(processes, after(processes))
+	if !flat {
+
+		var sortChildren func(process *Process)
+
+		sortChildren = func(process *Process) {
+			sort.Slice(process.Children, after(process.Children))
+			for _, child := range process.Children {
+				sortChildren(child)
+			}
+		}
+	}
+
+	return processes, processCount, goroutineCount, err
+}
diff --git a/modules/process/manager_test.go b/modules/process/manager_test.go
index 152c7a9235..30eabeb37a 100644
--- a/modules/process/manager_test.go
+++ b/modules/process/manager_test.go
@@ -22,7 +22,7 @@ func TestGetManager(t *testing.T) {
 }
 
 func TestManager_AddContext(t *testing.T) {
-	pm := Manager{processes: make(map[IDType]*Process), next: 1}
+	pm := Manager{processMap: make(map[IDType]*process), next: 1}
 
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
@@ -41,7 +41,7 @@ func TestManager_AddContext(t *testing.T) {
 }
 
 func TestManager_Cancel(t *testing.T) {
-	pm := Manager{processes: make(map[IDType]*Process), next: 1}
+	pm := Manager{processMap: make(map[IDType]*process), next: 1}
 
 	ctx, _, finished := pm.AddContext(context.Background(), "foo")
 	defer finished()
@@ -69,7 +69,7 @@ func TestManager_Cancel(t *testing.T) {
 }
 
 func TestManager_Remove(t *testing.T) {
-	pm := Manager{processes: make(map[IDType]*Process), next: 1}
+	pm := Manager{processMap: make(map[IDType]*process), next: 1}
 
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
@@ -85,7 +85,7 @@ func TestManager_Remove(t *testing.T) {
 
 	pm.Remove(GetPID(p2Ctx))
 
-	_, exists := pm.processes[GetPID(p2Ctx)]
+	_, exists := pm.processMap[GetPID(p2Ctx)]
 	assert.False(t, exists, "PID %d is in the list but shouldn't", GetPID(p2Ctx))
 }
 
diff --git a/modules/process/process.go b/modules/process/process.go
index 662f878d7f..2f7ea18373 100644
--- a/modules/process/process.go
+++ b/modules/process/process.go
@@ -6,61 +6,34 @@ package process
 
 import (
 	"context"
-	"sync"
 	"time"
 )
 
-// Process represents a working process inheriting from Gitea.
-type Process struct {
+var (
+	SystemProcessType  = "system"
+	RequestProcessType = "request"
+	NormalProcessType  = "normal"
+	NoneProcessType    = "none"
+)
+
+// process represents a working process inheriting from Gitea.
+type process struct {
 	PID         IDType // Process ID, not system one.
 	ParentPID   IDType
 	Description string
 	Start       time.Time
 	Cancel      context.CancelFunc
-
-	lock     sync.Mutex
-	children []*Process
-}
-
-// Children gets the children of the process
-// Note: this function will behave nicely even if p is nil
-func (p *Process) Children() (children []*Process) {
-	if p == nil {
-		return
-	}
-
-	p.lock.Lock()
-	defer p.lock.Unlock()
-	children = make([]*Process, len(p.children))
-	copy(children, p.children)
-	return children
+	Type        string
 }
 
-// AddChild adds a child process
-// Note: this function will behave nicely even if p is nil
-func (p *Process) AddChild(child *Process) {
-	if p == nil {
-		return
-	}
-
-	p.lock.Lock()
-	defer p.lock.Unlock()
-	p.children = append(p.children, child)
-}
-
-// RemoveChild removes a child process
-// Note: this function will behave nicely even if p is nil
-func (p *Process) RemoveChild(process *Process) {
-	if p == nil {
-		return
-	}
-
-	p.lock.Lock()
-	defer p.lock.Unlock()
-	for i, child := range p.children {
-		if child == process {
-			p.children = append(p.children[:i], p.children[i+1:]...)
-			return
-		}
+// ToProcess converts a process to a externally usable Process
+func (p *process) toProcess() *Process {
+	process := &Process{
+		PID:         p.PID,
+		ParentPID:   p.ParentPID,
+		Description: p.Description,
+		Start:       p.Start,
+		Type:        p.Type,
 	}
+	return process
 }