event.go

Documentation: internal/trace/v2

     1  // Copyright 2023 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package trace
     6  
     7  import (
     8  	"fmt"
     9  	"math"
    10  	"strings"
    11  	"time"
    12  
    13  	"internal/trace/v2/event"
    14  	"internal/trace/v2/event/go122"
    15  	"internal/trace/v2/version"
    16  )
    17  
    18  // EventKind indicates the kind of event this is.
    19  //
    20  // Use this information to obtain a more specific event that
    21  // allows access to more detailed information.
    22  type EventKind uint16
    23  
    24  const (
    25  	EventBad EventKind = iota
    26  
    27  	// EventKindSync is an event that indicates a global synchronization
    28  	// point in the trace. At the point of a sync event, the
    29  	// trace reader can be certain that all resources (e.g. threads,
    30  	// goroutines) that have existed until that point have been enumerated.
    31  	EventSync
    32  
    33  	// EventMetric is an event that represents the value of a metric at
    34  	// a particular point in time.
    35  	EventMetric
    36  
    37  	// EventLabel attaches a label to a resource.
    38  	EventLabel
    39  
    40  	// EventStackSample represents an execution sample, indicating what a
    41  	// thread/proc/goroutine was doing at a particular point in time via
    42  	// its backtrace.
    43  	//
    44  	// Note: Samples should be considered a close approximation of
    45  	// what a thread/proc/goroutine was executing at a given point in time.
    46  	// These events may slightly contradict the situation StateTransitions
    47  	// describe, so they should only be treated as a best-effort annotation.
    48  	EventStackSample
    49  
    50  	// EventRangeBegin and EventRangeEnd are a pair of generic events representing
    51  	// a special range of time. Ranges are named and scoped to some resource
    52  	// (identified via ResourceKind). A range that has begun but has not ended
    53  	// is considered active.
    54  	//
    55  	// EvRangeBegin and EvRangeEnd will share the same name, and an End will always
    56  	// follow a Begin on the same instance of the resource. The associated
    57  	// resource ID can be obtained from the Event. ResourceNone indicates the
    58  	// range is globally scoped. That is, any goroutine/proc/thread can start or
    59  	// stop, but only one such range may be active at any given time.
    60  	//
    61  	// EventRangeActive is like EventRangeBegin, but indicates that the range was
    62  	// already active. In this case, the resource referenced may not be in the current
    63  	// context.
    64  	EventRangeBegin
    65  	EventRangeActive
    66  	EventRangeEnd
    67  
    68  	// EvTaskBegin and EvTaskEnd are a pair of events representing a runtime/trace.Task.
    69  	EventTaskBegin
    70  	EventTaskEnd
    71  
    72  	// EventRegionBegin and EventRegionEnd are a pair of events represent a runtime/trace.Region.
    73  	EventRegionBegin
    74  	EventRegionEnd
    75  
    76  	// EventLog represents a runtime/trace.Log call.
    77  	EventLog
    78  
    79  	// Transitions in state for some resource.
    80  	EventStateTransition
    81  )
    82  
    83  // String returns a string form of the EventKind.
    84  func (e EventKind) String() string {
    85  	if int(e) >= len(eventKindStrings) {
    86  		return eventKindStrings[0]
    87  	}
    88  	return eventKindStrings[e]
    89  }
    90  
    91  var eventKindStrings = [...]string{
    92  	EventBad:             "Bad",
    93  	EventSync:            "Sync",
    94  	EventMetric:          "Metric",
    95  	EventLabel:           "Label",
    96  	EventStackSample:     "StackSample",
    97  	EventRangeBegin:      "RangeBegin",
    98  	EventRangeActive:     "RangeActive",
    99  	EventRangeEnd:        "RangeEnd",
   100  	EventTaskBegin:       "TaskBegin",
   101  	EventTaskEnd:         "TaskEnd",
   102  	EventRegionBegin:     "RegionBegin",
   103  	EventRegionEnd:       "RegionEnd",
   104  	EventLog:             "Log",
   105  	EventStateTransition: "StateTransition",
   106  }
   107  
   108  const maxTime = Time(math.MaxInt64)
   109  
   110  // Time is a timestamp in nanoseconds.
   111  //
   112  // It corresponds to the monotonic clock on the platform that the
   113  // trace was taken, and so is possible to correlate with timestamps
   114  // for other traces taken on the same machine using the same clock
   115  // (i.e. no reboots in between).
   116  //
   117  // The actual absolute value of the timestamp is only meaningful in
   118  // relation to other timestamps from the same clock.
   119  //
   120  // BUG: Timestamps coming from traces on Windows platforms are
   121  // only comparable with timestamps from the same trace. Timestamps
   122  // across traces cannot be compared, because the system clock is
   123  // not used as of Go 1.22.
   124  //
   125  // BUG: Traces produced by Go versions 1.21 and earlier cannot be
   126  // compared with timestamps from other traces taken on the same
   127  // machine. This is because the system clock was not used at all
   128  // to collect those timestamps.
   129  type Time int64
   130  
   131  // Sub subtracts t0 from t, returning the duration in nanoseconds.
   132  func (t Time) Sub(t0 Time) time.Duration {
   133  	return time.Duration(int64(t) - int64(t0))
   134  }
   135  
   136  // Metric provides details about a Metric event.
   137  type Metric struct {
   138  	// Name is the name of the sampled metric.
   139  	//
   140  	// Names follow the same convention as metric names in the
   141  	// runtime/metrics package, meaning they include the unit.
   142  	// Names that match with the runtime/metrics package represent
   143  	// the same quantity. Note that this corresponds to the
   144  	// runtime/metrics package for the Go version this trace was
   145  	// collected for.
   146  	Name string
   147  
   148  	// Value is the sampled value of the metric.
   149  	//
   150  	// The Value's Kind is tied to the name of the metric, and so is
   151  	// guaranteed to be the same for metric samples for the same metric.
   152  	Value Value
   153  }
   154  
   155  // Label provides details about a Label event.
   156  type Label struct {
   157  	// Label is the label applied to some resource.
   158  	Label string
   159  
   160  	// Resource is the resource to which this label should be applied.
   161  	Resource ResourceID
   162  }
   163  
   164  // Range provides details about a Range event.
   165  type Range struct {
   166  	// Name is a human-readable name for the range.
   167  	//
   168  	// This name can be used to identify the end of the range for the resource
   169  	// its scoped to, because only one of each type of range may be active on
   170  	// a particular resource. The relevant resource should be obtained from the
   171  	// Event that produced these details. The corresponding RangeEnd will have
   172  	// an identical name.
   173  	Name string
   174  
   175  	// Scope is the resource that the range is scoped to.
   176  	//
   177  	// For example, a ResourceGoroutine scope means that the same goroutine
   178  	// must have a start and end for the range, and that goroutine can only
   179  	// have one range of a particular name active at any given time. The
   180  	// ID that this range is scoped to may be obtained via Event.Goroutine.
   181  	//
   182  	// The ResourceNone scope means that the range is globally scoped. As a
   183  	// result, any goroutine/proc/thread may start or end the range, and only
   184  	// one such named range may be active globally at any given time.
   185  	//
   186  	// For RangeBegin and RangeEnd events, this will always reference some
   187  	// resource ID in the current execution context. For RangeActive events,
   188  	// this may reference a resource not in the current context. Prefer Scope
   189  	// over the current execution context.
   190  	Scope ResourceID
   191  }
   192  
   193  // RangeAttributes provides attributes about a completed Range.
   194  type RangeAttribute struct {
   195  	// Name is the human-readable name for the range.
   196  	Name string
   197  
   198  	// Value is the value of the attribute.
   199  	Value Value
   200  }
   201  
   202  // TaskID is the internal ID of a task used to disambiguate tasks (even if they
   203  // are of the same type).
   204  type TaskID uint64
   205  
   206  const (
   207  	// NoTask indicates the lack of a task.
   208  	NoTask = TaskID(^uint64(0))
   209  
   210  	// BackgroundTask is the global task that events are attached to if there was
   211  	// no other task in the context at the point the event was emitted.
   212  	BackgroundTask = TaskID(0)
   213  )
   214  
   215  // Task provides details about a Task event.
   216  type Task struct {
   217  	// ID is a unique identifier for the task.
   218  	//
   219  	// This can be used to associate the beginning of a task with its end.
   220  	ID TaskID
   221  
   222  	// ParentID is the ID of the parent task.
   223  	Parent TaskID
   224  
   225  	// Type is the taskType that was passed to runtime/trace.NewTask.
   226  	//
   227  	// May be "" if a task's TaskBegin event isn't present in the trace.
   228  	Type string
   229  }
   230  
   231  // Region provides details about a Region event.
   232  type Region struct {
   233  	// Task is the ID of the task this region is associated with.
   234  	Task TaskID
   235  
   236  	// Type is the regionType that was passed to runtime/trace.StartRegion or runtime/trace.WithRegion.
   237  	Type string
   238  }
   239  
   240  // Log provides details about a Log event.
   241  type Log struct {
   242  	// Task is the ID of the task this region is associated with.
   243  	Task TaskID
   244  
   245  	// Category is the category that was passed to runtime/trace.Log or runtime/trace.Logf.
   246  	Category string
   247  
   248  	// Message is the message that was passed to runtime/trace.Log or runtime/trace.Logf.
   249  	Message string
   250  }
   251  
   252  // Stack represents a stack. It's really a handle to a stack and it's trivially comparable.
   253  //
   254  // If two Stacks are equal then their Frames are guaranteed to be identical. If they are not
   255  // equal, however, their Frames may still be equal.
   256  type Stack struct {
   257  	table *evTable
   258  	id    stackID
   259  }
   260  
   261  // Frames is an iterator over the frames in a Stack.
   262  func (s Stack) Frames(yield func(f StackFrame) bool) bool {
   263  	if s.id == 0 {
   264  		return true
   265  	}
   266  	stk := s.table.stacks.mustGet(s.id)
   267  	for _, f := range stk.frames {
   268  		sf := StackFrame{
   269  			PC:   f.pc,
   270  			Func: s.table.strings.mustGet(f.funcID),
   271  			File: s.table.strings.mustGet(f.fileID),
   272  			Line: f.line,
   273  		}
   274  		if !yield(sf) {
   275  			return false
   276  		}
   277  	}
   278  	return true
   279  }
   280  
   281  // NoStack is a sentinel value that can be compared against any Stack value, indicating
   282  // a lack of a stack trace.
   283  var NoStack = Stack{}
   284  
   285  // StackFrame represents a single frame of a stack.
   286  type StackFrame struct {
   287  	// PC is the program counter of the function call if this
   288  	// is not a leaf frame. If it's a leaf frame, it's the point
   289  	// at which the stack trace was taken.
   290  	PC uint64
   291  
   292  	// Func is the name of the function this frame maps to.
   293  	Func string
   294  
   295  	// File is the file which contains the source code of Func.
   296  	File string
   297  
   298  	// Line is the line number within File which maps to PC.
   299  	Line uint64
   300  }
   301  
   302  // Event represents a single event in the trace.
   303  type Event struct {
   304  	table *evTable
   305  	ctx   schedCtx
   306  	base  baseEvent
   307  }
   308  
   309  // Kind returns the kind of event that this is.
   310  func (e Event) Kind() EventKind {
   311  	return go122Type2Kind[e.base.typ]
   312  }
   313  
   314  // Time returns the timestamp of the event.
   315  func (e Event) Time() Time {
   316  	return e.base.time
   317  }
   318  
   319  // Goroutine returns the ID of the goroutine that was executing when
   320  // this event happened. It describes part of the execution context
   321  // for this event.
   322  //
   323  // Note that for goroutine state transitions this always refers to the
   324  // state before the transition. For example, if a goroutine is just
   325  // starting to run on this thread and/or proc, then this will return
   326  // NoGoroutine. In this case, the goroutine starting to run will be
   327  // can be found at Event.StateTransition().Resource.
   328  func (e Event) Goroutine() GoID {
   329  	return e.ctx.G
   330  }
   331  
   332  // Proc returns the ID of the proc this event event pertains to.
   333  //
   334  // Note that for proc state transitions this always refers to the
   335  // state before the transition. For example, if a proc is just
   336  // starting to run on this thread, then this will return NoProc.
   337  func (e Event) Proc() ProcID {
   338  	return e.ctx.P
   339  }
   340  
   341  // Thread returns the ID of the thread this event pertains to.
   342  //
   343  // Note that for thread state transitions this always refers to the
   344  // state before the transition. For example, if a thread is just
   345  // starting to run, then this will return NoThread.
   346  //
   347  // Note: tracking thread state is not currently supported, so this
   348  // will always return a valid thread ID. However thread state transitions
   349  // may be tracked in the future, and callers must be robust to this
   350  // possibility.
   351  func (e Event) Thread() ThreadID {
   352  	return e.ctx.M
   353  }
   354  
   355  // Stack returns a handle to a stack associated with the event.
   356  //
   357  // This represents a stack trace at the current moment in time for
   358  // the current execution context.
   359  func (e Event) Stack() Stack {
   360  	if e.base.typ == evSync {
   361  		return NoStack
   362  	}
   363  	if e.base.typ == go122.EvCPUSample {
   364  		return Stack{table: e.table, id: stackID(e.base.args[0])}
   365  	}
   366  	spec := go122.Specs()[e.base.typ]
   367  	if len(spec.StackIDs) == 0 {
   368  		return NoStack
   369  	}
   370  	// The stack for the main execution context is always the
   371  	// first stack listed in StackIDs. Subtract one from this
   372  	// because we've peeled away the timestamp argument.
   373  	id := stackID(e.base.args[spec.StackIDs[0]-1])
   374  	if id == 0 {
   375  		return NoStack
   376  	}
   377  	return Stack{table: e.table, id: id}
   378  }
   379  
   380  // Metric returns details about a Metric event.
   381  //
   382  // Panics if Kind != EventMetric.
   383  func (e Event) Metric() Metric {
   384  	if e.Kind() != EventMetric {
   385  		panic("Metric called on non-Metric event")
   386  	}
   387  	var m Metric
   388  	switch e.base.typ {
   389  	case go122.EvProcsChange:
   390  		m.Name = "/sched/gomaxprocs:threads"
   391  		m.Value = Value{kind: ValueUint64, scalar: e.base.args[0]}
   392  	case go122.EvHeapAlloc:
   393  		m.Name = "/memory/classes/heap/objects:bytes"
   394  		m.Value = Value{kind: ValueUint64, scalar: e.base.args[0]}
   395  	case go122.EvHeapGoal:
   396  		m.Name = "/gc/heap/goal:bytes"
   397  		m.Value = Value{kind: ValueUint64, scalar: e.base.args[0]}
   398  	default:
   399  		panic(fmt.Sprintf("internal error: unexpected event type for Metric kind: %s", go122.EventString(e.base.typ)))
   400  	}
   401  	return m
   402  }
   403  
   404  // Label returns details about a Label event.
   405  //
   406  // Panics if Kind != EventLabel.
   407  func (e Event) Label() Label {
   408  	if e.Kind() != EventLabel {
   409  		panic("Label called on non-Label event")
   410  	}
   411  	if e.base.typ != go122.EvGoLabel {
   412  		panic(fmt.Sprintf("internal error: unexpected event type for Label kind: %s", go122.EventString(e.base.typ)))
   413  	}
   414  	return Label{
   415  		Label:    e.table.strings.mustGet(stringID(e.base.args[0])),
   416  		Resource: ResourceID{Kind: ResourceGoroutine, id: int64(e.ctx.G)},
   417  	}
   418  }
   419  
   420  // Range returns details about an EventRangeBegin, EventRangeActive, or EventRangeEnd event.
   421  //
   422  // Panics if Kind != EventRangeBegin, Kind != EventRangeActive, and Kind != EventRangeEnd.
   423  func (e Event) Range() Range {
   424  	if kind := e.Kind(); kind != EventRangeBegin && kind != EventRangeActive && kind != EventRangeEnd {
   425  		panic("Range called on non-Range event")
   426  	}
   427  	var r Range
   428  	switch e.base.typ {
   429  	case go122.EvSTWBegin, go122.EvSTWEnd:
   430  		// N.B. ordering.advance smuggles in the STW reason as e.base.args[0]
   431  		// for go122.EvSTWEnd (it's already there for Begin).
   432  		r.Name = "stop-the-world (" + e.table.strings.mustGet(stringID(e.base.args[0])) + ")"
   433  		r.Scope = ResourceID{Kind: ResourceGoroutine, id: int64(e.Goroutine())}
   434  	case go122.EvGCBegin, go122.EvGCActive, go122.EvGCEnd:
   435  		r.Name = "GC concurrent mark phase"
   436  		r.Scope = ResourceID{Kind: ResourceNone}
   437  	case go122.EvGCSweepBegin, go122.EvGCSweepActive, go122.EvGCSweepEnd:
   438  		r.Name = "GC incremental sweep"
   439  		r.Scope = ResourceID{Kind: ResourceProc}
   440  		if e.base.typ == go122.EvGCSweepActive {
   441  			r.Scope.id = int64(e.base.args[0])
   442  		} else {
   443  			r.Scope.id = int64(e.Proc())
   444  		}
   445  		r.Scope.id = int64(e.Proc())
   446  	case go122.EvGCMarkAssistBegin, go122.EvGCMarkAssistActive, go122.EvGCMarkAssistEnd:
   447  		r.Name = "GC mark assist"
   448  		r.Scope = ResourceID{Kind: ResourceGoroutine}
   449  		if e.base.typ == go122.EvGCMarkAssistActive {
   450  			r.Scope.id = int64(e.base.args[0])
   451  		} else {
   452  			r.Scope.id = int64(e.Goroutine())
   453  		}
   454  	default:
   455  		panic(fmt.Sprintf("internal error: unexpected event type for Range kind: %s", go122.EventString(e.base.typ)))
   456  	}
   457  	return r
   458  }
   459  
   460  // RangeAttributes returns attributes for a completed range.
   461  //
   462  // Panics if Kind != EventRangeEnd.
   463  func (e Event) RangeAttributes() []RangeAttribute {
   464  	if e.Kind() != EventRangeEnd {
   465  		panic("Range called on non-Range event")
   466  	}
   467  	if e.base.typ != go122.EvGCSweepEnd {
   468  		return nil
   469  	}
   470  	return []RangeAttribute{
   471  		{
   472  			Name:  "bytes swept",
   473  			Value: Value{kind: ValueUint64, scalar: e.base.args[0]},
   474  		},
   475  		{
   476  			Name:  "bytes reclaimed",
   477  			Value: Value{kind: ValueUint64, scalar: e.base.args[1]},
   478  		},
   479  	}
   480  }
   481  
   482  // Task returns details about a TaskBegin or TaskEnd event.
   483  //
   484  // Panics if Kind != EventTaskBegin and Kind != EventTaskEnd.
   485  func (e Event) Task() Task {
   486  	if kind := e.Kind(); kind != EventTaskBegin && kind != EventTaskEnd {
   487  		panic("Task called on non-Task event")
   488  	}
   489  	parentID := NoTask
   490  	var typ string
   491  	switch e.base.typ {
   492  	case go122.EvUserTaskBegin:
   493  		parentID = TaskID(e.base.args[1])
   494  		typ = e.table.strings.mustGet(stringID(e.base.args[2]))
   495  	case go122.EvUserTaskEnd:
   496  		parentID = TaskID(e.base.extra(version.Go122)[0])
   497  		typ = e.table.getExtraString(extraStringID(e.base.extra(version.Go122)[1]))
   498  	default:
   499  		panic(fmt.Sprintf("internal error: unexpected event type for Task kind: %s", go122.EventString(e.base.typ)))
   500  	}
   501  	return Task{
   502  		ID:     TaskID(e.base.args[0]),
   503  		Parent: parentID,
   504  		Type:   typ,
   505  	}
   506  }
   507  
   508  // Region returns details about a RegionBegin or RegionEnd event.
   509  //
   510  // Panics if Kind != EventRegionBegin and Kind != EventRegionEnd.
   511  func (e Event) Region() Region {
   512  	if kind := e.Kind(); kind != EventRegionBegin && kind != EventRegionEnd {
   513  		panic("Region called on non-Region event")
   514  	}
   515  	if e.base.typ != go122.EvUserRegionBegin && e.base.typ != go122.EvUserRegionEnd {
   516  		panic(fmt.Sprintf("internal error: unexpected event type for Region kind: %s", go122.EventString(e.base.typ)))
   517  	}
   518  	return Region{
   519  		Task: TaskID(e.base.args[0]),
   520  		Type: e.table.strings.mustGet(stringID(e.base.args[1])),
   521  	}
   522  }
   523  
   524  // Log returns details about a Log event.
   525  //
   526  // Panics if Kind != EventLog.
   527  func (e Event) Log() Log {
   528  	if e.Kind() != EventLog {
   529  		panic("Log called on non-Log event")
   530  	}
   531  	if e.base.typ != go122.EvUserLog {
   532  		panic(fmt.Sprintf("internal error: unexpected event type for Log kind: %s", go122.EventString(e.base.typ)))
   533  	}
   534  	return Log{
   535  		Task:     TaskID(e.base.args[0]),
   536  		Category: e.table.strings.mustGet(stringID(e.base.args[1])),
   537  		Message:  e.table.strings.mustGet(stringID(e.base.args[2])),
   538  	}
   539  }
   540  
   541  // StateTransition returns details about a StateTransition event.
   542  //
   543  // Panics if Kind != EventStateTransition.
   544  func (e Event) StateTransition() StateTransition {
   545  	if e.Kind() != EventStateTransition {
   546  		panic("StateTransition called on non-StateTransition event")
   547  	}
   548  	var s StateTransition
   549  	switch e.base.typ {
   550  	case go122.EvProcStart:
   551  		s = procStateTransition(ProcID(e.base.args[0]), ProcIdle, ProcRunning)
   552  	case go122.EvProcStop:
   553  		s = procStateTransition(e.ctx.P, ProcRunning, ProcIdle)
   554  	case go122.EvProcSteal:
   555  		// N.B. ordering.advance populates e.base.extra.
   556  		beforeState := ProcRunning
   557  		if go122.ProcStatus(e.base.extra(version.Go122)[0]) == go122.ProcSyscallAbandoned {
   558  			// We've lost information because this ProcSteal advanced on a
   559  			// SyscallAbandoned state. Treat the P as idle because ProcStatus
   560  			// treats SyscallAbandoned as Idle. Otherwise we'll have an invalid
   561  			// transition.
   562  			beforeState = ProcIdle
   563  		}
   564  		s = procStateTransition(ProcID(e.base.args[0]), beforeState, ProcIdle)
   565  	case go122.EvProcStatus:
   566  		// N.B. ordering.advance populates e.base.extra.
   567  		s = procStateTransition(ProcID(e.base.args[0]), ProcState(e.base.extra(version.Go122)[0]), go122ProcStatus2ProcState[e.base.args[1]])
   568  	case go122.EvGoCreate:
   569  		s = goStateTransition(GoID(e.base.args[0]), GoNotExist, GoRunnable)
   570  		s.Stack = Stack{table: e.table, id: stackID(e.base.args[1])}
   571  	case go122.EvGoCreateSyscall:
   572  		s = goStateTransition(GoID(e.base.args[0]), GoNotExist, GoSyscall)
   573  	case go122.EvGoStart:
   574  		s = goStateTransition(GoID(e.base.args[0]), GoRunnable, GoRunning)
   575  	case go122.EvGoDestroy:
   576  		s = goStateTransition(e.ctx.G, GoRunning, GoNotExist)
   577  		s.Stack = e.Stack() // This event references the resource the event happened on.
   578  	case go122.EvGoDestroySyscall:
   579  		s = goStateTransition(e.ctx.G, GoSyscall, GoNotExist)
   580  	case go122.EvGoStop:
   581  		s = goStateTransition(e.ctx.G, GoRunning, GoRunnable)
   582  		s.Reason = e.table.strings.mustGet(stringID(e.base.args[0]))
   583  		s.Stack = e.Stack() // This event references the resource the event happened on.
   584  	case go122.EvGoBlock:
   585  		s = goStateTransition(e.ctx.G, GoRunning, GoWaiting)
   586  		s.Reason = e.table.strings.mustGet(stringID(e.base.args[0]))
   587  		s.Stack = e.Stack() // This event references the resource the event happened on.
   588  	case go122.EvGoUnblock:
   589  		s = goStateTransition(GoID(e.base.args[0]), GoWaiting, GoRunnable)
   590  	case go122.EvGoSyscallBegin:
   591  		s = goStateTransition(e.ctx.G, GoRunning, GoSyscall)
   592  		s.Stack = e.Stack() // This event references the resource the event happened on.
   593  	case go122.EvGoSyscallEnd:
   594  		s = goStateTransition(e.ctx.G, GoSyscall, GoRunning)
   595  		s.Stack = e.Stack() // This event references the resource the event happened on.
   596  	case go122.EvGoSyscallEndBlocked:
   597  		s = goStateTransition(e.ctx.G, GoSyscall, GoRunnable)
   598  		s.Stack = e.Stack() // This event references the resource the event happened on.
   599  	case go122.EvGoStatus:
   600  		// N.B. ordering.advance populates e.base.extra.
   601  		s = goStateTransition(GoID(e.base.args[0]), GoState(e.base.extra(version.Go122)[0]), go122GoStatus2GoState[e.base.args[2]])
   602  	default:
   603  		panic(fmt.Sprintf("internal error: unexpected event type for StateTransition kind: %s", go122.EventString(e.base.typ)))
   604  	}
   605  	return s
   606  }
   607  
   608  const evSync = ^event.Type(0)
   609  
   610  var go122Type2Kind = [...]EventKind{
   611  	go122.EvCPUSample:           EventStackSample,
   612  	go122.EvProcsChange:         EventMetric,
   613  	go122.EvProcStart:           EventStateTransition,
   614  	go122.EvProcStop:            EventStateTransition,
   615  	go122.EvProcSteal:           EventStateTransition,
   616  	go122.EvProcStatus:          EventStateTransition,
   617  	go122.EvGoCreate:            EventStateTransition,
   618  	go122.EvGoCreateSyscall:     EventStateTransition,
   619  	go122.EvGoStart:             EventStateTransition,
   620  	go122.EvGoDestroy:           EventStateTransition,
   621  	go122.EvGoDestroySyscall:    EventStateTransition,
   622  	go122.EvGoStop:              EventStateTransition,
   623  	go122.EvGoBlock:             EventStateTransition,
   624  	go122.EvGoUnblock:           EventStateTransition,
   625  	go122.EvGoSyscallBegin:      EventStateTransition,
   626  	go122.EvGoSyscallEnd:        EventStateTransition,
   627  	go122.EvGoSyscallEndBlocked: EventStateTransition,
   628  	go122.EvGoStatus:            EventStateTransition,
   629  	go122.EvSTWBegin:            EventRangeBegin,
   630  	go122.EvSTWEnd:              EventRangeEnd,
   631  	go122.EvGCActive:            EventRangeActive,
   632  	go122.EvGCBegin:             EventRangeBegin,
   633  	go122.EvGCEnd:               EventRangeEnd,
   634  	go122.EvGCSweepActive:       EventRangeActive,
   635  	go122.EvGCSweepBegin:        EventRangeBegin,
   636  	go122.EvGCSweepEnd:          EventRangeEnd,
   637  	go122.EvGCMarkAssistActive:  EventRangeActive,
   638  	go122.EvGCMarkAssistBegin:   EventRangeBegin,
   639  	go122.EvGCMarkAssistEnd:     EventRangeEnd,
   640  	go122.EvHeapAlloc:           EventMetric,
   641  	go122.EvHeapGoal:            EventMetric,
   642  	go122.EvGoLabel:             EventLabel,
   643  	go122.EvUserTaskBegin:       EventTaskBegin,
   644  	go122.EvUserTaskEnd:         EventTaskEnd,
   645  	go122.EvUserRegionBegin:     EventRegionBegin,
   646  	go122.EvUserRegionEnd:       EventRegionEnd,
   647  	go122.EvUserLog:             EventLog,
   648  	evSync:                      EventSync,
   649  }
   650  
   651  var go122GoStatus2GoState = [...]GoState{
   652  	go122.GoRunnable: GoRunnable,
   653  	go122.GoRunning:  GoRunning,
   654  	go122.GoWaiting:  GoWaiting,
   655  	go122.GoSyscall:  GoSyscall,
   656  }
   657  
   658  var go122ProcStatus2ProcState = [...]ProcState{
   659  	go122.ProcRunning:          ProcRunning,
   660  	go122.ProcIdle:             ProcIdle,
   661  	go122.ProcSyscall:          ProcRunning,
   662  	go122.ProcSyscallAbandoned: ProcIdle,
   663  }
   664  
   665  // String returns the event as a human-readable string.
   666  //
   667  // The format of the string is intended for debugging and is subject to change.
   668  func (e Event) String() string {
   669  	var sb strings.Builder
   670  	fmt.Fprintf(&sb, "M=%d P=%d G=%d", e.Thread(), e.Proc(), e.Goroutine())
   671  	fmt.Fprintf(&sb, " %s Time=%d", e.Kind(), e.Time())
   672  	// Kind-specific fields.
   673  	switch kind := e.Kind(); kind {
   674  	case EventMetric:
   675  		m := e.Metric()
   676  		fmt.Fprintf(&sb, " Name=%q Value=%s", m.Name, valueAsString(m.Value))
   677  	case EventLabel:
   678  		l := e.Label()
   679  		fmt.Fprintf(&sb, " Label=%q Resource=%s", l.Label, l.Resource)
   680  	case EventRangeBegin, EventRangeActive, EventRangeEnd:
   681  		r := e.Range()
   682  		fmt.Fprintf(&sb, " Name=%q Scope=%s", r.Name, r.Scope)
   683  		if kind == EventRangeEnd {
   684  			fmt.Fprintf(&sb, " Attributes=[")
   685  			for i, attr := range e.RangeAttributes() {
   686  				if i != 0 {
   687  					fmt.Fprintf(&sb, " ")
   688  				}
   689  				fmt.Fprintf(&sb, "%q=%s", attr.Name, valueAsString(attr.Value))
   690  			}
   691  			fmt.Fprintf(&sb, "]")
   692  		}
   693  	case EventTaskBegin, EventTaskEnd:
   694  		t := e.Task()
   695  		fmt.Fprintf(&sb, " ID=%d Parent=%d Type=%q", t.ID, t.Parent, t.Type)
   696  	case EventRegionBegin, EventRegionEnd:
   697  		r := e.Region()
   698  		fmt.Fprintf(&sb, " Task=%d Type=%q", r.Task, r.Type)
   699  	case EventLog:
   700  		l := e.Log()
   701  		fmt.Fprintf(&sb, " Task=%d Category=%q Message=%q", l.Task, l.Category, l.Message)
   702  	case EventStateTransition:
   703  		s := e.StateTransition()
   704  		fmt.Fprintf(&sb, " Resource=%s Reason=%q", s.Resource, s.Reason)
   705  		switch s.Resource.Kind {
   706  		case ResourceGoroutine:
   707  			id := s.Resource.Goroutine()
   708  			old, new := s.Goroutine()
   709  			fmt.Fprintf(&sb, " GoID=%d %s->%s", id, old, new)
   710  		case ResourceProc:
   711  			id := s.Resource.Proc()
   712  			old, new := s.Proc()
   713  			fmt.Fprintf(&sb, " ProcID=%d %s->%s", id, old, new)
   714  		}
   715  		if s.Stack != NoStack {
   716  			fmt.Fprintln(&sb)
   717  			fmt.Fprintln(&sb, "TransitionStack=")
   718  			s.Stack.Frames(func(f StackFrame) bool {
   719  				fmt.Fprintf(&sb, "\t%s @ 0x%x\n", f.Func, f.PC)
   720  				fmt.Fprintf(&sb, "\t\t%s:%d\n", f.File, f.Line)
   721  				return true
   722  			})
   723  		}
   724  	}
   725  	if stk := e.Stack(); stk != NoStack {
   726  		fmt.Fprintln(&sb)
   727  		fmt.Fprintln(&sb, "Stack=")
   728  		stk.Frames(func(f StackFrame) bool {
   729  			fmt.Fprintf(&sb, "\t%s @ 0x%x\n", f.Func, f.PC)
   730  			fmt.Fprintf(&sb, "\t\t%s:%d\n", f.File, f.Line)
   731  			return true
   732  		})
   733  	}
   734  	return sb.String()
   735  }
   736  
   737  // validateTableIDs checks to make sure lookups in e.table
   738  // will work.
   739  func (e Event) validateTableIDs() error {
   740  	if e.base.typ == evSync {
   741  		return nil
   742  	}
   743  	spec := go122.Specs()[e.base.typ]
   744  
   745  	// Check stacks.
   746  	for _, i := range spec.StackIDs {
   747  		id := stackID(e.base.args[i-1])
   748  		_, ok := e.table.stacks.get(id)
   749  		if !ok {
   750  			return fmt.Errorf("found invalid stack ID %d for event %s", id, spec.Name)
   751  		}
   752  	}
   753  	// N.B. Strings referenced by stack frames are validated
   754  	// early on, when reading the stacks in to begin with.
   755  
   756  	// Check strings.
   757  	for _, i := range spec.StringIDs {
   758  		id := stringID(e.base.args[i-1])
   759  		_, ok := e.table.strings.get(id)
   760  		if !ok {
   761  			return fmt.Errorf("found invalid string ID %d for event %s", id, spec.Name)
   762  		}
   763  	}
   764  	return nil
   765  }
   766  
   767  func syncEvent(table *evTable, ts Time) Event {
   768  	return Event{
   769  		table: table,
   770  		ctx: schedCtx{
   771  			G: NoGoroutine,
   772  			P: NoProc,
   773  			M: NoThread,
   774  		},
   775  		base: baseEvent{
   776  			typ:  evSync,
   777  			time: ts,
   778  		},
   779  	}
   780  }
   781
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