Source file src/runtime/trace.go

Documentation: runtime

     1  // Copyright 2014 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  // Go execution tracer.
     6  // The tracer captures a wide range of execution events like goroutine
     7  // creation/blocking/unblocking, syscall enter/exit/block, GC-related events,
     8  // changes of heap size, processor start/stop, etc and writes them to a buffer
     9  // in a compact form. A precise nanosecond-precision timestamp and a stack
    10  // trace is captured for most events.
    11  // See https://golang.org/s/go15trace for more info.
    12  
    13  package runtime
    14  
    15  import (
    16  	"runtime/internal/sys"
    17  	"unsafe"
    18  )
    19  
    20  // Event types in the trace, args are given in square brackets.
    21  const (
    22  	traceEvNone              = 0  // unused
    23  	traceEvBatch             = 1  // start of per-P batch of events [pid, timestamp]
    24  	traceEvFrequency         = 2  // contains tracer timer frequency [frequency (ticks per second)]
    25  	traceEvStack             = 3  // stack [stack id, number of PCs, array of {PC, func string ID, file string ID, line}]
    26  	traceEvGomaxprocs        = 4  // current value of GOMAXPROCS [timestamp, GOMAXPROCS, stack id]
    27  	traceEvProcStart         = 5  // start of P [timestamp, thread id]
    28  	traceEvProcStop          = 6  // stop of P [timestamp]
    29  	traceEvGCStart           = 7  // GC start [timestamp, seq, stack id]
    30  	traceEvGCDone            = 8  // GC done [timestamp]
    31  	traceEvGCSTWStart        = 9  // GC STW start [timestamp, kind]
    32  	traceEvGCSTWDone         = 10 // GC STW done [timestamp]
    33  	traceEvGCSweepStart      = 11 // GC sweep start [timestamp, stack id]
    34  	traceEvGCSweepDone       = 12 // GC sweep done [timestamp, swept, reclaimed]
    35  	traceEvGoCreate          = 13 // goroutine creation [timestamp, new goroutine id, new stack id, stack id]
    36  	traceEvGoStart           = 14 // goroutine starts running [timestamp, goroutine id, seq]
    37  	traceEvGoEnd             = 15 // goroutine ends [timestamp]
    38  	traceEvGoStop            = 16 // goroutine stops (like in select{}) [timestamp, stack]
    39  	traceEvGoSched           = 17 // goroutine calls Gosched [timestamp, stack]
    40  	traceEvGoPreempt         = 18 // goroutine is preempted [timestamp, stack]
    41  	traceEvGoSleep           = 19 // goroutine calls Sleep [timestamp, stack]
    42  	traceEvGoBlock           = 20 // goroutine blocks [timestamp, stack]
    43  	traceEvGoUnblock         = 21 // goroutine is unblocked [timestamp, goroutine id, seq, stack]
    44  	traceEvGoBlockSend       = 22 // goroutine blocks on chan send [timestamp, stack]
    45  	traceEvGoBlockRecv       = 23 // goroutine blocks on chan recv [timestamp, stack]
    46  	traceEvGoBlockSelect     = 24 // goroutine blocks on select [timestamp, stack]
    47  	traceEvGoBlockSync       = 25 // goroutine blocks on Mutex/RWMutex [timestamp, stack]
    48  	traceEvGoBlockCond       = 26 // goroutine blocks on Cond [timestamp, stack]
    49  	traceEvGoBlockNet        = 27 // goroutine blocks on network [timestamp, stack]
    50  	traceEvGoSysCall         = 28 // syscall enter [timestamp, stack]
    51  	traceEvGoSysExit         = 29 // syscall exit [timestamp, goroutine id, seq, real timestamp]
    52  	traceEvGoSysBlock        = 30 // syscall blocks [timestamp]
    53  	traceEvGoWaiting         = 31 // denotes that goroutine is blocked when tracing starts [timestamp, goroutine id]
    54  	traceEvGoInSyscall       = 32 // denotes that goroutine is in syscall when tracing starts [timestamp, goroutine id]
    55  	traceEvHeapAlloc         = 33 // memstats.heap_live change [timestamp, heap_alloc]
    56  	traceEvNextGC            = 34 // memstats.next_gc change [timestamp, next_gc]
    57  	traceEvTimerGoroutine    = 35 // not currently used; previously denoted timer goroutine [timer goroutine id]
    58  	traceEvFutileWakeup      = 36 // denotes that the previous wakeup of this goroutine was futile [timestamp]
    59  	traceEvString            = 37 // string dictionary entry [ID, length, string]
    60  	traceEvGoStartLocal      = 38 // goroutine starts running on the same P as the last event [timestamp, goroutine id]
    61  	traceEvGoUnblockLocal    = 39 // goroutine is unblocked on the same P as the last event [timestamp, goroutine id, stack]
    62  	traceEvGoSysExitLocal    = 40 // syscall exit on the same P as the last event [timestamp, goroutine id, real timestamp]
    63  	traceEvGoStartLabel      = 41 // goroutine starts running with label [timestamp, goroutine id, seq, label string id]
    64  	traceEvGoBlockGC         = 42 // goroutine blocks on GC assist [timestamp, stack]
    65  	traceEvGCMarkAssistStart = 43 // GC mark assist start [timestamp, stack]
    66  	traceEvGCMarkAssistDone  = 44 // GC mark assist done [timestamp]
    67  	traceEvUserTaskCreate    = 45 // trace.NewContext [timestamp, internal task id, internal parent task id, stack, name string]
    68  	traceEvUserTaskEnd       = 46 // end of a task [timestamp, internal task id, stack]
    69  	traceEvUserRegion        = 47 // trace.WithRegion [timestamp, internal task id, mode(0:start, 1:end), stack, name string]
    70  	traceEvUserLog           = 48 // trace.Log [timestamp, internal task id, key string id, stack, value string]
    71  	traceEvCount             = 49
    72  	// Byte is used but only 6 bits are available for event type.
    73  	// The remaining 2 bits are used to specify the number of arguments.
    74  	// That means, the max event type value is 63.
    75  )
    76  
    77  const (
    78  	// Timestamps in trace are cputicks/traceTickDiv.
    79  	// This makes absolute values of timestamp diffs smaller,
    80  	// and so they are encoded in less number of bytes.
    81  	// 64 on x86 is somewhat arbitrary (one tick is ~20ns on a 3GHz machine).
    82  	// The suggested increment frequency for PowerPC's time base register is
    83  	// 512 MHz according to Power ISA v2.07 section 6.2, so we use 16 on ppc64
    84  	// and ppc64le.
    85  	// Tracing won't work reliably for architectures where cputicks is emulated
    86  	// by nanotime, so the value doesn't matter for those architectures.
    87  	traceTickDiv = 16 + 48*(sys.Goarch386|sys.GoarchAmd64)
    88  	// Maximum number of PCs in a single stack trace.
    89  	// Since events contain only stack id rather than whole stack trace,
    90  	// we can allow quite large values here.
    91  	traceStackSize = 128
    92  	// Identifier of a fake P that is used when we trace without a real P.
    93  	traceGlobProc = -1
    94  	// Maximum number of bytes to encode uint64 in base-128.
    95  	traceBytesPerNumber = 10
    96  	// Shift of the number of arguments in the first event byte.
    97  	traceArgCountShift = 6
    98  	// Flag passed to traceGoPark to denote that the previous wakeup of this
    99  	// goroutine was futile. For example, a goroutine was unblocked on a mutex,
   100  	// but another goroutine got ahead and acquired the mutex before the first
   101  	// goroutine is scheduled, so the first goroutine has to block again.
   102  	// Such wakeups happen on buffered channels and sync.Mutex,
   103  	// but are generally not interesting for end user.
   104  	traceFutileWakeup byte = 128
   105  )
   106  
   107  // trace is global tracing context.
   108  var trace struct {
   109  	lock          mutex       // protects the following members
   110  	lockOwner     *g          // to avoid deadlocks during recursive lock locks
   111  	enabled       bool        // when set runtime traces events
   112  	shutdown      bool        // set when we are waiting for trace reader to finish after setting enabled to false
   113  	headerWritten bool        // whether ReadTrace has emitted trace header
   114  	footerWritten bool        // whether ReadTrace has emitted trace footer
   115  	shutdownSema  uint32      // used to wait for ReadTrace completion
   116  	seqStart      uint64      // sequence number when tracing was started
   117  	ticksStart    int64       // cputicks when tracing was started
   118  	ticksEnd      int64       // cputicks when tracing was stopped
   119  	timeStart     int64       // nanotime when tracing was started
   120  	timeEnd       int64       // nanotime when tracing was stopped
   121  	seqGC         uint64      // GC start/done sequencer
   122  	reading       traceBufPtr // buffer currently handed off to user
   123  	empty         traceBufPtr // stack of empty buffers
   124  	fullHead      traceBufPtr // queue of full buffers
   125  	fullTail      traceBufPtr
   126  	reader        guintptr        // goroutine that called ReadTrace, or nil
   127  	stackTab      traceStackTable // maps stack traces to unique ids
   128  
   129  	// Dictionary for traceEvString.
   130  	//
   131  	// TODO: central lock to access the map is not ideal.
   132  	//   option: pre-assign ids to all user annotation region names and tags
   133  	//   option: per-P cache
   134  	//   option: sync.Map like data structure
   135  	stringsLock mutex
   136  	strings     map[string]uint64
   137  	stringSeq   uint64
   138  
   139  	// markWorkerLabels maps gcMarkWorkerMode to string ID.
   140  	markWorkerLabels [len(gcMarkWorkerModeStrings)]uint64
   141  
   142  	bufLock mutex       // protects buf
   143  	buf     traceBufPtr // global trace buffer, used when running without a p
   144  }
   145  
   146  // traceBufHeader is per-P tracing buffer.
   147  type traceBufHeader struct {
   148  	link      traceBufPtr             // in trace.empty/full
   149  	lastTicks uint64                  // when we wrote the last event
   150  	pos       int                     // next write offset in arr
   151  	stk       [traceStackSize]uintptr // scratch buffer for traceback
   152  }
   153  
   154  // traceBuf is per-P tracing buffer.
   155  //
   156  //go:notinheap
   157  type traceBuf struct {
   158  	traceBufHeader
   159  	arr [64<<10 - unsafe.Sizeof(traceBufHeader{})]byte // underlying buffer for traceBufHeader.buf
   160  }
   161  
   162  // traceBufPtr is a *traceBuf that is not traced by the garbage
   163  // collector and doesn't have write barriers. traceBufs are not
   164  // allocated from the GC'd heap, so this is safe, and are often
   165  // manipulated in contexts where write barriers are not allowed, so
   166  // this is necessary.
   167  //
   168  // TODO: Since traceBuf is now go:notinheap, this isn't necessary.
   169  type traceBufPtr uintptr
   170  
   171  func (tp traceBufPtr) ptr() *traceBuf   { return (*traceBuf)(unsafe.Pointer(tp)) }
   172  func (tp *traceBufPtr) set(b *traceBuf) { *tp = traceBufPtr(unsafe.Pointer(b)) }
   173  func traceBufPtrOf(b *traceBuf) traceBufPtr {
   174  	return traceBufPtr(unsafe.Pointer(b))
   175  }
   176  
   177  // StartTrace enables tracing for the current process.
   178  // While tracing, the data will be buffered and available via ReadTrace.
   179  // StartTrace returns an error if tracing is already enabled.
   180  // Most clients should use the runtime/trace package or the testing package's
   181  // -test.trace flag instead of calling StartTrace directly.
   182  func StartTrace() error {
   183  	// Stop the world, so that we can take a consistent snapshot
   184  	// of all goroutines at the beginning of the trace.
   185  	stopTheWorld("start tracing")
   186  
   187  	// We are in stop-the-world, but syscalls can finish and write to trace concurrently.
   188  	// Exitsyscall could check trace.enabled long before and then suddenly wake up
   189  	// and decide to write to trace at a random point in time.
   190  	// However, such syscall will use the global trace.buf buffer, because we've
   191  	// acquired all p's by doing stop-the-world. So this protects us from such races.
   192  	lock(&trace.bufLock)
   193  
   194  	if trace.enabled || trace.shutdown {
   195  		unlock(&trace.bufLock)
   196  		startTheWorld()
   197  		return errorString("tracing is already enabled")
   198  	}
   199  
   200  	// Can't set trace.enabled yet. While the world is stopped, exitsyscall could
   201  	// already emit a delayed event (see exitTicks in exitsyscall) if we set trace.enabled here.
   202  	// That would lead to an inconsistent trace:
   203  	// - either GoSysExit appears before EvGoInSyscall,
   204  	// - or GoSysExit appears for a goroutine for which we don't emit EvGoInSyscall below.
   205  	// To instruct traceEvent that it must not ignore events below, we set startingtrace.
   206  	// trace.enabled is set afterwards once we have emitted all preliminary events.
   207  	_g_ := getg()
   208  	_g_.m.startingtrace = true
   209  
   210  	// Obtain current stack ID to use in all traceEvGoCreate events below.
   211  	mp := acquirem()
   212  	stkBuf := make([]uintptr, traceStackSize)
   213  	stackID := traceStackID(mp, stkBuf, 2)
   214  	releasem(mp)
   215  
   216  	for _, gp := range allgs {
   217  		status := readgstatus(gp)
   218  		if status != _Gdead {
   219  			gp.traceseq = 0
   220  			gp.tracelastp = getg().m.p
   221  			// +PCQuantum because traceFrameForPC expects return PCs and subtracts PCQuantum.
   222  			id := trace.stackTab.put([]uintptr{gp.startpc + sys.PCQuantum})
   223  			traceEvent(traceEvGoCreate, -1, uint64(gp.goid), uint64(id), stackID)
   224  		}
   225  		if status == _Gwaiting {
   226  			// traceEvGoWaiting is implied to have seq=1.
   227  			gp.traceseq++
   228  			traceEvent(traceEvGoWaiting, -1, uint64(gp.goid))
   229  		}
   230  		if status == _Gsyscall {
   231  			gp.traceseq++
   232  			traceEvent(traceEvGoInSyscall, -1, uint64(gp.goid))
   233  		} else {
   234  			gp.sysblocktraced = false
   235  		}
   236  	}
   237  	traceProcStart()
   238  	traceGoStart()
   239  	// Note: ticksStart needs to be set after we emit traceEvGoInSyscall events.
   240  	// If we do it the other way around, it is possible that exitsyscall will
   241  	// query sysexitticks after ticksStart but before traceEvGoInSyscall timestamp.
   242  	// It will lead to a false conclusion that cputicks is broken.
   243  	trace.ticksStart = cputicks()
   244  	trace.timeStart = nanotime()
   245  	trace.headerWritten = false
   246  	trace.footerWritten = false
   247  
   248  	// string to id mapping
   249  	//  0 : reserved for an empty string
   250  	//  remaining: other strings registered by traceString
   251  	trace.stringSeq = 0
   252  	trace.strings = make(map[string]uint64)
   253  
   254  	trace.seqGC = 0
   255  	_g_.m.startingtrace = false
   256  	trace.enabled = true
   257  
   258  	// Register runtime goroutine labels.
   259  	_, pid, bufp := traceAcquireBuffer()
   260  	for i, label := range gcMarkWorkerModeStrings[:] {
   261  		trace.markWorkerLabels[i], bufp = traceString(bufp, pid, label)
   262  	}
   263  	traceReleaseBuffer(pid)
   264  
   265  	unlock(&trace.bufLock)
   266  
   267  	startTheWorld()
   268  	return nil
   269  }
   270  
   271  // StopTrace stops tracing, if it was previously enabled.
   272  // StopTrace only returns after all the reads for the trace have completed.
   273  func StopTrace() {
   274  	// Stop the world so that we can collect the trace buffers from all p's below,
   275  	// and also to avoid races with traceEvent.
   276  	stopTheWorld("stop tracing")
   277  
   278  	// See the comment in StartTrace.
   279  	lock(&trace.bufLock)
   280  
   281  	if !trace.enabled {
   282  		unlock(&trace.bufLock)
   283  		startTheWorld()
   284  		return
   285  	}
   286  
   287  	traceGoSched()
   288  
   289  	// Loop over all allocated Ps because dead Ps may still have
   290  	// trace buffers.
   291  	for _, p := range allp[:cap(allp)] {
   292  		buf := p.tracebuf
   293  		if buf != 0 {
   294  			traceFullQueue(buf)
   295  			p.tracebuf = 0
   296  		}
   297  	}
   298  	if trace.buf != 0 {
   299  		buf := trace.buf
   300  		trace.buf = 0
   301  		if buf.ptr().pos != 0 {
   302  			traceFullQueue(buf)
   303  		}
   304  	}
   305  
   306  	for {
   307  		trace.ticksEnd = cputicks()
   308  		trace.timeEnd = nanotime()
   309  		// Windows time can tick only every 15ms, wait for at least one tick.
   310  		if trace.timeEnd != trace.timeStart {
   311  			break
   312  		}
   313  		osyield()
   314  	}
   315  
   316  	trace.enabled = false
   317  	trace.shutdown = true
   318  	unlock(&trace.bufLock)
   319  
   320  	startTheWorld()
   321  
   322  	// The world is started but we've set trace.shutdown, so new tracing can't start.
   323  	// Wait for the trace reader to flush pending buffers and stop.
   324  	semacquire(&trace.shutdownSema)
   325  	if raceenabled {
   326  		raceacquire(unsafe.Pointer(&trace.shutdownSema))
   327  	}
   328  
   329  	// The lock protects us from races with StartTrace/StopTrace because they do stop-the-world.
   330  	lock(&trace.lock)
   331  	for _, p := range allp[:cap(allp)] {
   332  		if p.tracebuf != 0 {
   333  			throw("trace: non-empty trace buffer in proc")
   334  		}
   335  	}
   336  	if trace.buf != 0 {
   337  		throw("trace: non-empty global trace buffer")
   338  	}
   339  	if trace.fullHead != 0 || trace.fullTail != 0 {
   340  		throw("trace: non-empty full trace buffer")
   341  	}
   342  	if trace.reading != 0 || trace.reader != 0 {
   343  		throw("trace: reading after shutdown")
   344  	}
   345  	for trace.empty != 0 {
   346  		buf := trace.empty
   347  		trace.empty = buf.ptr().link
   348  		sysFree(unsafe.Pointer(buf), unsafe.Sizeof(*buf.ptr()), &memstats.other_sys)
   349  	}
   350  	trace.strings = nil
   351  	trace.shutdown = false
   352  	unlock(&trace.lock)
   353  }
   354  
   355  // ReadTrace returns the next chunk of binary tracing data, blocking until data
   356  // is available. If tracing is turned off and all the data accumulated while it
   357  // was on has been returned, ReadTrace returns nil. The caller must copy the
   358  // returned data before calling ReadTrace again.
   359  // ReadTrace must be called from one goroutine at a time.
   360  func ReadTrace() []byte {
   361  	// This function may need to lock trace.lock recursively
   362  	// (goparkunlock -> traceGoPark -> traceEvent -> traceFlush).
   363  	// To allow this we use trace.lockOwner.
   364  	// Also this function must not allocate while holding trace.lock:
   365  	// allocation can call heap allocate, which will try to emit a trace
   366  	// event while holding heap lock.
   367  	lock(&trace.lock)
   368  	trace.lockOwner = getg()
   369  
   370  	if trace.reader != 0 {
   371  		// More than one goroutine reads trace. This is bad.
   372  		// But we rather do not crash the program because of tracing,
   373  		// because tracing can be enabled at runtime on prod servers.
   374  		trace.lockOwner = nil
   375  		unlock(&trace.lock)
   376  		println("runtime: ReadTrace called from multiple goroutines simultaneously")
   377  		return nil
   378  	}
   379  	// Recycle the old buffer.
   380  	if buf := trace.reading; buf != 0 {
   381  		buf.ptr().link = trace.empty
   382  		trace.empty = buf
   383  		trace.reading = 0
   384  	}
   385  	// Write trace header.
   386  	if !trace.headerWritten {
   387  		trace.headerWritten = true
   388  		trace.lockOwner = nil
   389  		unlock(&trace.lock)
   390  		return []byte("go 1.11 trace\x00\x00\x00")
   391  	}
   392  	// Wait for new data.
   393  	if trace.fullHead == 0 && !trace.shutdown {
   394  		trace.reader.set(getg())
   395  		goparkunlock(&trace.lock, waitReasonTraceReaderBlocked, traceEvGoBlock, 2)
   396  		lock(&trace.lock)
   397  	}
   398  	// Write a buffer.
   399  	if trace.fullHead != 0 {
   400  		buf := traceFullDequeue()
   401  		trace.reading = buf
   402  		trace.lockOwner = nil
   403  		unlock(&trace.lock)
   404  		return buf.ptr().arr[:buf.ptr().pos]
   405  	}
   406  	// Write footer with timer frequency.
   407  	if !trace.footerWritten {
   408  		trace.footerWritten = true
   409  		// Use float64 because (trace.ticksEnd - trace.ticksStart) * 1e9 can overflow int64.
   410  		freq := float64(trace.ticksEnd-trace.ticksStart) * 1e9 / float64(trace.timeEnd-trace.timeStart) / traceTickDiv
   411  		trace.lockOwner = nil
   412  		unlock(&trace.lock)
   413  		var data []byte
   414  		data = append(data, traceEvFrequency|0<<traceArgCountShift)
   415  		data = traceAppend(data, uint64(freq))
   416  		// This will emit a bunch of full buffers, we will pick them up
   417  		// on the next iteration.
   418  		trace.stackTab.dump()
   419  		return data
   420  	}
   421  	// Done.
   422  	if trace.shutdown {
   423  		trace.lockOwner = nil
   424  		unlock(&trace.lock)
   425  		if raceenabled {
   426  			// Model synchronization on trace.shutdownSema, which race
   427  			// detector does not see. This is required to avoid false
   428  			// race reports on writer passed to trace.Start.
   429  			racerelease(unsafe.Pointer(&trace.shutdownSema))
   430  		}
   431  		// trace.enabled is already reset, so can call traceable functions.
   432  		semrelease(&trace.shutdownSema)
   433  		return nil
   434  	}
   435  	// Also bad, but see the comment above.
   436  	trace.lockOwner = nil
   437  	unlock(&trace.lock)
   438  	println("runtime: spurious wakeup of trace reader")
   439  	return nil
   440  }
   441  
   442  // traceReader returns the trace reader that should be woken up, if any.
   443  func traceReader() *g {
   444  	if trace.reader == 0 || (trace.fullHead == 0 && !trace.shutdown) {
   445  		return nil
   446  	}
   447  	lock(&trace.lock)
   448  	if trace.reader == 0 || (trace.fullHead == 0 && !trace.shutdown) {
   449  		unlock(&trace.lock)
   450  		return nil
   451  	}
   452  	gp := trace.reader.ptr()
   453  	trace.reader.set(nil)
   454  	unlock(&trace.lock)
   455  	return gp
   456  }
   457  
   458  // traceProcFree frees trace buffer associated with pp.
   459  func traceProcFree(pp *p) {
   460  	buf := pp.tracebuf
   461  	pp.tracebuf = 0
   462  	if buf == 0 {
   463  		return
   464  	}
   465  	lock(&trace.lock)
   466  	traceFullQueue(buf)
   467  	unlock(&trace.lock)
   468  }
   469  
   470  // traceFullQueue queues buf into queue of full buffers.
   471  func traceFullQueue(buf traceBufPtr) {
   472  	buf.ptr().link = 0
   473  	if trace.fullHead == 0 {
   474  		trace.fullHead = buf
   475  	} else {
   476  		trace.fullTail.ptr().link = buf
   477  	}
   478  	trace.fullTail = buf
   479  }
   480  
   481  // traceFullDequeue dequeues from queue of full buffers.
   482  func traceFullDequeue() traceBufPtr {
   483  	buf := trace.fullHead
   484  	if buf == 0 {
   485  		return 0
   486  	}
   487  	trace.fullHead = buf.ptr().link
   488  	if trace.fullHead == 0 {
   489  		trace.fullTail = 0
   490  	}
   491  	buf.ptr().link = 0
   492  	return buf
   493  }
   494  
   495  // traceEvent writes a single event to trace buffer, flushing the buffer if necessary.
   496  // ev is event type.
   497  // If skip > 0, write current stack id as the last argument (skipping skip top frames).
   498  // If skip = 0, this event type should contain a stack, but we don't want
   499  // to collect and remember it for this particular call.
   500  func traceEvent(ev byte, skip int, args ...uint64) {
   501  	mp, pid, bufp := traceAcquireBuffer()
   502  	// Double-check trace.enabled now that we've done m.locks++ and acquired bufLock.
   503  	// This protects from races between traceEvent and StartTrace/StopTrace.
   504  
   505  	// The caller checked that trace.enabled == true, but trace.enabled might have been
   506  	// turned off between the check and now. Check again. traceLockBuffer did mp.locks++,
   507  	// StopTrace does stopTheWorld, and stopTheWorld waits for mp.locks to go back to zero,
   508  	// so if we see trace.enabled == true now, we know it's true for the rest of the function.
   509  	// Exitsyscall can run even during stopTheWorld. The race with StartTrace/StopTrace
   510  	// during tracing in exitsyscall is resolved by locking trace.bufLock in traceLockBuffer.
   511  	//
   512  	// Note trace_userTaskCreate runs the same check.
   513  	if !trace.enabled && !mp.startingtrace {
   514  		traceReleaseBuffer(pid)
   515  		return
   516  	}
   517  
   518  	if skip > 0 {
   519  		if getg() == mp.curg {
   520  			skip++ // +1 because stack is captured in traceEventLocked.
   521  		}
   522  	}
   523  	traceEventLocked(0, mp, pid, bufp, ev, skip, args...)
   524  	traceReleaseBuffer(pid)
   525  }
   526  
   527  func traceEventLocked(extraBytes int, mp *m, pid int32, bufp *traceBufPtr, ev byte, skip int, args ...uint64) {
   528  	buf := bufp.ptr()
   529  	// TODO: test on non-zero extraBytes param.
   530  	maxSize := 2 + 5*traceBytesPerNumber + extraBytes // event type, length, sequence, timestamp, stack id and two add params
   531  	if buf == nil || len(buf.arr)-buf.pos < maxSize {
   532  		buf = traceFlush(traceBufPtrOf(buf), pid).ptr()
   533  		bufp.set(buf)
   534  	}
   535  
   536  	ticks := uint64(cputicks()) / traceTickDiv
   537  	tickDiff := ticks - buf.lastTicks
   538  	buf.lastTicks = ticks
   539  	narg := byte(len(args))
   540  	if skip >= 0 {
   541  		narg++
   542  	}
   543  	// We have only 2 bits for number of arguments.
   544  	// If number is >= 3, then the event type is followed by event length in bytes.
   545  	if narg > 3 {
   546  		narg = 3
   547  	}
   548  	startPos := buf.pos
   549  	buf.byte(ev | narg<<traceArgCountShift)
   550  	var lenp *byte
   551  	if narg == 3 {
   552  		// Reserve the byte for length assuming that length < 128.
   553  		buf.varint(0)
   554  		lenp = &buf.arr[buf.pos-1]
   555  	}
   556  	buf.varint(tickDiff)
   557  	for _, a := range args {
   558  		buf.varint(a)
   559  	}
   560  	if skip == 0 {
   561  		buf.varint(0)
   562  	} else if skip > 0 {
   563  		buf.varint(traceStackID(mp, buf.stk[:], skip))
   564  	}
   565  	evSize := buf.pos - startPos
   566  	if evSize > maxSize {
   567  		throw("invalid length of trace event")
   568  	}
   569  	if lenp != nil {
   570  		// Fill in actual length.
   571  		*lenp = byte(evSize - 2)
   572  	}
   573  }
   574  
   575  func traceStackID(mp *m, buf []uintptr, skip int) uint64 {
   576  	_g_ := getg()
   577  	gp := mp.curg
   578  	var nstk int
   579  	if gp == _g_ {
   580  		nstk = callers(skip+1, buf)
   581  	} else if gp != nil {
   582  		gp = mp.curg
   583  		nstk = gcallers(gp, skip, buf)
   584  	}
   585  	if nstk > 0 {
   586  		nstk-- // skip runtime.goexit
   587  	}
   588  	if nstk > 0 && gp.goid == 1 {
   589  		nstk-- // skip runtime.main
   590  	}
   591  	id := trace.stackTab.put(buf[:nstk])
   592  	return uint64(id)
   593  }
   594  
   595  // traceAcquireBuffer returns trace buffer to use and, if necessary, locks it.
   596  func traceAcquireBuffer() (mp *m, pid int32, bufp *traceBufPtr) {
   597  	mp = acquirem()
   598  	if p := mp.p.ptr(); p != nil {
   599  		return mp, p.id, &p.tracebuf
   600  	}
   601  	lock(&trace.bufLock)
   602  	return mp, traceGlobProc, &trace.buf
   603  }
   604  
   605  // traceReleaseBuffer releases a buffer previously acquired with traceAcquireBuffer.
   606  func traceReleaseBuffer(pid int32) {
   607  	if pid == traceGlobProc {
   608  		unlock(&trace.bufLock)
   609  	}
   610  	releasem(getg().m)
   611  }
   612  
   613  // traceFlush puts buf onto stack of full buffers and returns an empty buffer.
   614  func traceFlush(buf traceBufPtr, pid int32) traceBufPtr {
   615  	owner := trace.lockOwner
   616  	dolock := owner == nil || owner != getg().m.curg
   617  	if dolock {
   618  		lock(&trace.lock)
   619  	}
   620  	if buf != 0 {
   621  		traceFullQueue(buf)
   622  	}
   623  	if trace.empty != 0 {
   624  		buf = trace.empty
   625  		trace.empty = buf.ptr().link
   626  	} else {
   627  		buf = traceBufPtr(sysAlloc(unsafe.Sizeof(traceBuf{}), &memstats.other_sys))
   628  		if buf == 0 {
   629  			throw("trace: out of memory")
   630  		}
   631  	}
   632  	bufp := buf.ptr()
   633  	bufp.link.set(nil)
   634  	bufp.pos = 0
   635  
   636  	// initialize the buffer for a new batch
   637  	ticks := uint64(cputicks()) / traceTickDiv
   638  	bufp.lastTicks = ticks
   639  	bufp.byte(traceEvBatch | 1<<traceArgCountShift)
   640  	bufp.varint(uint64(pid))
   641  	bufp.varint(ticks)
   642  
   643  	if dolock {
   644  		unlock(&trace.lock)
   645  	}
   646  	return buf
   647  }
   648  
   649  // traceString adds a string to the trace.strings and returns the id.
   650  func traceString(bufp *traceBufPtr, pid int32, s string) (uint64, *traceBufPtr) {
   651  	if s == "" {
   652  		return 0, bufp
   653  	}
   654  
   655  	lock(&trace.stringsLock)
   656  	if raceenabled {
   657  		// raceacquire is necessary because the map access
   658  		// below is race annotated.
   659  		raceacquire(unsafe.Pointer(&trace.stringsLock))
   660  	}
   661  
   662  	if id, ok := trace.strings[s]; ok {
   663  		if raceenabled {
   664  			racerelease(unsafe.Pointer(&trace.stringsLock))
   665  		}
   666  		unlock(&trace.stringsLock)
   667  
   668  		return id, bufp
   669  	}
   670  
   671  	trace.stringSeq++
   672  	id := trace.stringSeq
   673  	trace.strings[s] = id
   674  
   675  	if raceenabled {
   676  		racerelease(unsafe.Pointer(&trace.stringsLock))
   677  	}
   678  	unlock(&trace.stringsLock)
   679  
   680  	// memory allocation in above may trigger tracing and
   681  	// cause *bufp changes. Following code now works with *bufp,
   682  	// so there must be no memory allocation or any activities
   683  	// that causes tracing after this point.
   684  
   685  	buf := bufp.ptr()
   686  	size := 1 + 2*traceBytesPerNumber + len(s)
   687  	if buf == nil || len(buf.arr)-buf.pos < size {
   688  		buf = traceFlush(traceBufPtrOf(buf), pid).ptr()
   689  		bufp.set(buf)
   690  	}
   691  	buf.byte(traceEvString)
   692  	buf.varint(id)
   693  
   694  	// double-check the string and the length can fit.
   695  	// Otherwise, truncate the string.
   696  	slen := len(s)
   697  	if room := len(buf.arr) - buf.pos; room < slen+traceBytesPerNumber {
   698  		slen = room
   699  	}
   700  
   701  	buf.varint(uint64(slen))
   702  	buf.pos += copy(buf.arr[buf.pos:], s[:slen])
   703  
   704  	bufp.set(buf)
   705  	return id, bufp
   706  }
   707  
   708  // traceAppend appends v to buf in little-endian-base-128 encoding.
   709  func traceAppend(buf []byte, v uint64) []byte {
   710  	for ; v >= 0x80; v >>= 7 {
   711  		buf = append(buf, 0x80|byte(v))
   712  	}
   713  	buf = append(buf, byte(v))
   714  	return buf
   715  }
   716  
   717  // varint appends v to buf in little-endian-base-128 encoding.
   718  func (buf *traceBuf) varint(v uint64) {
   719  	pos := buf.pos
   720  	for ; v >= 0x80; v >>= 7 {
   721  		buf.arr[pos] = 0x80 | byte(v)
   722  		pos++
   723  	}
   724  	buf.arr[pos] = byte(v)
   725  	pos++
   726  	buf.pos = pos
   727  }
   728  
   729  // byte appends v to buf.
   730  func (buf *traceBuf) byte(v byte) {
   731  	buf.arr[buf.pos] = v
   732  	buf.pos++
   733  }
   734  
   735  // traceStackTable maps stack traces (arrays of PC's) to unique uint32 ids.
   736  // It is lock-free for reading.
   737  type traceStackTable struct {
   738  	lock mutex
   739  	seq  uint32
   740  	mem  traceAlloc
   741  	tab  [1 << 13]traceStackPtr
   742  }
   743  
   744  // traceStack is a single stack in traceStackTable.
   745  type traceStack struct {
   746  	link traceStackPtr
   747  	hash uintptr
   748  	id   uint32
   749  	n    int
   750  	stk  [0]uintptr // real type [n]uintptr
   751  }
   752  
   753  type traceStackPtr uintptr
   754  
   755  func (tp traceStackPtr) ptr() *traceStack { return (*traceStack)(unsafe.Pointer(tp)) }
   756  
   757  // stack returns slice of PCs.
   758  func (ts *traceStack) stack() []uintptr {
   759  	return (*[traceStackSize]uintptr)(unsafe.Pointer(&ts.stk))[:ts.n]
   760  }
   761  
   762  // put returns a unique id for the stack trace pcs and caches it in the table,
   763  // if it sees the trace for the first time.
   764  func (tab *traceStackTable) put(pcs []uintptr) uint32 {
   765  	if len(pcs) == 0 {
   766  		return 0
   767  	}
   768  	hash := memhash(unsafe.Pointer(&pcs[0]), 0, uintptr(len(pcs))*unsafe.Sizeof(pcs[0]))
   769  	// First, search the hashtable w/o the mutex.
   770  	if id := tab.find(pcs, hash); id != 0 {
   771  		return id
   772  	}
   773  	// Now, double check under the mutex.
   774  	lock(&tab.lock)
   775  	if id := tab.find(pcs, hash); id != 0 {
   776  		unlock(&tab.lock)
   777  		return id
   778  	}
   779  	// Create new record.
   780  	tab.seq++
   781  	stk := tab.newStack(len(pcs))
   782  	stk.hash = hash
   783  	stk.id = tab.seq
   784  	stk.n = len(pcs)
   785  	stkpc := stk.stack()
   786  	for i, pc := range pcs {
   787  		stkpc[i] = pc
   788  	}
   789  	part := int(hash % uintptr(len(tab.tab)))
   790  	stk.link = tab.tab[part]
   791  	atomicstorep(unsafe.Pointer(&tab.tab[part]), unsafe.Pointer(stk))
   792  	unlock(&tab.lock)
   793  	return stk.id
   794  }
   795  
   796  // find checks if the stack trace pcs is already present in the table.
   797  func (tab *traceStackTable) find(pcs []uintptr, hash uintptr) uint32 {
   798  	part := int(hash % uintptr(len(tab.tab)))
   799  Search:
   800  	for stk := tab.tab[part].ptr(); stk != nil; stk = stk.link.ptr() {
   801  		if stk.hash == hash && stk.n == len(pcs) {
   802  			for i, stkpc := range stk.stack() {
   803  				if stkpc != pcs[i] {
   804  					continue Search
   805  				}
   806  			}
   807  			return stk.id
   808  		}
   809  	}
   810  	return 0
   811  }
   812  
   813  // newStack allocates a new stack of size n.
   814  func (tab *traceStackTable) newStack(n int) *traceStack {
   815  	return (*traceStack)(tab.mem.alloc(unsafe.Sizeof(traceStack{}) + uintptr(n)*sys.PtrSize))
   816  }
   817  
   818  // allFrames returns all of the Frames corresponding to pcs.
   819  func allFrames(pcs []uintptr) []Frame {
   820  	frames := make([]Frame, 0, len(pcs))
   821  	ci := CallersFrames(pcs)
   822  	for {
   823  		f, more := ci.Next()
   824  		frames = append(frames, f)
   825  		if !more {
   826  			return frames
   827  		}
   828  	}
   829  }
   830  
   831  // dump writes all previously cached stacks to trace buffers,
   832  // releases all memory and resets state.
   833  func (tab *traceStackTable) dump() {
   834  	var tmp [(2 + 4*traceStackSize) * traceBytesPerNumber]byte
   835  	bufp := traceFlush(0, 0)
   836  	for _, stk := range tab.tab {
   837  		stk := stk.ptr()
   838  		for ; stk != nil; stk = stk.link.ptr() {
   839  			tmpbuf := tmp[:0]
   840  			tmpbuf = traceAppend(tmpbuf, uint64(stk.id))
   841  			frames := allFrames(stk.stack())
   842  			tmpbuf = traceAppend(tmpbuf, uint64(len(frames)))
   843  			for _, f := range frames {
   844  				var frame traceFrame
   845  				frame, bufp = traceFrameForPC(bufp, 0, f)
   846  				tmpbuf = traceAppend(tmpbuf, uint64(f.PC))
   847  				tmpbuf = traceAppend(tmpbuf, uint64(frame.funcID))
   848  				tmpbuf = traceAppend(tmpbuf, uint64(frame.fileID))
   849  				tmpbuf = traceAppend(tmpbuf, uint64(frame.line))
   850  			}
   851  			// Now copy to the buffer.
   852  			size := 1 + traceBytesPerNumber + len(tmpbuf)
   853  			if buf := bufp.ptr(); len(buf.arr)-buf.pos < size {
   854  				bufp = traceFlush(bufp, 0)
   855  			}
   856  			buf := bufp.ptr()
   857  			buf.byte(traceEvStack | 3<<traceArgCountShift)
   858  			buf.varint(uint64(len(tmpbuf)))
   859  			buf.pos += copy(buf.arr[buf.pos:], tmpbuf)
   860  		}
   861  	}
   862  
   863  	lock(&trace.lock)
   864  	traceFullQueue(bufp)
   865  	unlock(&trace.lock)
   866  
   867  	tab.mem.drop()
   868  	*tab = traceStackTable{}
   869  }
   870  
   871  type traceFrame struct {
   872  	funcID uint64
   873  	fileID uint64
   874  	line   uint64
   875  }
   876  
   877  // traceFrameForPC records the frame information.
   878  // It may allocate memory.
   879  func traceFrameForPC(buf traceBufPtr, pid int32, f Frame) (traceFrame, traceBufPtr) {
   880  	bufp := &buf
   881  	var frame traceFrame
   882  
   883  	fn := f.Function
   884  	const maxLen = 1 << 10
   885  	if len(fn) > maxLen {
   886  		fn = fn[len(fn)-maxLen:]
   887  	}
   888  	frame.funcID, bufp = traceString(bufp, pid, fn)
   889  	frame.line = uint64(f.Line)
   890  	file := f.File
   891  	if len(file) > maxLen {
   892  		file = file[len(file)-maxLen:]
   893  	}
   894  	frame.fileID, bufp = traceString(bufp, pid, file)
   895  	return frame, (*bufp)
   896  }
   897  
   898  // traceAlloc is a non-thread-safe region allocator.
   899  // It holds a linked list of traceAllocBlock.
   900  type traceAlloc struct {
   901  	head traceAllocBlockPtr
   902  	off  uintptr
   903  }
   904  
   905  // traceAllocBlock is a block in traceAlloc.
   906  //
   907  // traceAllocBlock is allocated from non-GC'd memory, so it must not
   908  // contain heap pointers. Writes to pointers to traceAllocBlocks do
   909  // not need write barriers.
   910  //
   911  //go:notinheap
   912  type traceAllocBlock struct {
   913  	next traceAllocBlockPtr
   914  	data [64<<10 - sys.PtrSize]byte
   915  }
   916  
   917  // TODO: Since traceAllocBlock is now go:notinheap, this isn't necessary.
   918  type traceAllocBlockPtr uintptr
   919  
   920  func (p traceAllocBlockPtr) ptr() *traceAllocBlock   { return (*traceAllocBlock)(unsafe.Pointer(p)) }
   921  func (p *traceAllocBlockPtr) set(x *traceAllocBlock) { *p = traceAllocBlockPtr(unsafe.Pointer(x)) }
   922  
   923  // alloc allocates n-byte block.
   924  func (a *traceAlloc) alloc(n uintptr) unsafe.Pointer {
   925  	n = alignUp(n, sys.PtrSize)
   926  	if a.head == 0 || a.off+n > uintptr(len(a.head.ptr().data)) {
   927  		if n > uintptr(len(a.head.ptr().data)) {
   928  			throw("trace: alloc too large")
   929  		}
   930  		block := (*traceAllocBlock)(sysAlloc(unsafe.Sizeof(traceAllocBlock{}), &memstats.other_sys))
   931  		if block == nil {
   932  			throw("trace: out of memory")
   933  		}
   934  		block.next.set(a.head.ptr())
   935  		a.head.set(block)
   936  		a.off = 0
   937  	}
   938  	p := &a.head.ptr().data[a.off]
   939  	a.off += n
   940  	return unsafe.Pointer(p)
   941  }
   942  
   943  // drop frees all previously allocated memory and resets the allocator.
   944  func (a *traceAlloc) drop() {
   945  	for a.head != 0 {
   946  		block := a.head.ptr()
   947  		a.head.set(block.next.ptr())
   948  		sysFree(unsafe.Pointer(block), unsafe.Sizeof(traceAllocBlock{}), &memstats.other_sys)
   949  	}
   950  }
   951  
   952  // The following functions write specific events to trace.
   953  
   954  func traceGomaxprocs(procs int32) {
   955  	traceEvent(traceEvGomaxprocs, 1, uint64(procs))
   956  }
   957  
   958  func traceProcStart() {
   959  	traceEvent(traceEvProcStart, -1, uint64(getg().m.id))
   960  }
   961  
   962  func traceProcStop(pp *p) {
   963  	// Sysmon and stopTheWorld can stop Ps blocked in syscalls,
   964  	// to handle this we temporary employ the P.
   965  	mp := acquirem()
   966  	oldp := mp.p
   967  	mp.p.set(pp)
   968  	traceEvent(traceEvProcStop, -1)
   969  	mp.p = oldp
   970  	releasem(mp)
   971  }
   972  
   973  func traceGCStart() {
   974  	traceEvent(traceEvGCStart, 3, trace.seqGC)
   975  	trace.seqGC++
   976  }
   977  
   978  func traceGCDone() {
   979  	traceEvent(traceEvGCDone, -1)
   980  }
   981  
   982  func traceGCSTWStart(kind int) {
   983  	traceEvent(traceEvGCSTWStart, -1, uint64(kind))
   984  }
   985  
   986  func traceGCSTWDone() {
   987  	traceEvent(traceEvGCSTWDone, -1)
   988  }
   989  
   990  // traceGCSweepStart prepares to trace a sweep loop. This does not
   991  // emit any events until traceGCSweepSpan is called.
   992  //
   993  // traceGCSweepStart must be paired with traceGCSweepDone and there
   994  // must be no preemption points between these two calls.
   995  func traceGCSweepStart() {
   996  	// Delay the actual GCSweepStart event until the first span
   997  	// sweep. If we don't sweep anything, don't emit any events.
   998  	_p_ := getg().m.p.ptr()
   999  	if _p_.traceSweep {
  1000  		throw("double traceGCSweepStart")
  1001  	}
  1002  	_p_.traceSweep, _p_.traceSwept, _p_.traceReclaimed = true, 0, 0
  1003  }
  1004  
  1005  // traceGCSweepSpan traces the sweep of a single page.
  1006  //
  1007  // This may be called outside a traceGCSweepStart/traceGCSweepDone
  1008  // pair; however, it will not emit any trace events in this case.
  1009  func traceGCSweepSpan(bytesSwept uintptr) {
  1010  	_p_ := getg().m.p.ptr()
  1011  	if _p_.traceSweep {
  1012  		if _p_.traceSwept == 0 {
  1013  			traceEvent(traceEvGCSweepStart, 1)
  1014  		}
  1015  		_p_.traceSwept += bytesSwept
  1016  	}
  1017  }
  1018  
  1019  func traceGCSweepDone() {
  1020  	_p_ := getg().m.p.ptr()
  1021  	if !_p_.traceSweep {
  1022  		throw("missing traceGCSweepStart")
  1023  	}
  1024  	if _p_.traceSwept != 0 {
  1025  		traceEvent(traceEvGCSweepDone, -1, uint64(_p_.traceSwept), uint64(_p_.traceReclaimed))
  1026  	}
  1027  	_p_.traceSweep = false
  1028  }
  1029  
  1030  func traceGCMarkAssistStart() {
  1031  	traceEvent(traceEvGCMarkAssistStart, 1)
  1032  }
  1033  
  1034  func traceGCMarkAssistDone() {
  1035  	traceEvent(traceEvGCMarkAssistDone, -1)
  1036  }
  1037  
  1038  func traceGoCreate(newg *g, pc uintptr) {
  1039  	newg.traceseq = 0
  1040  	newg.tracelastp = getg().m.p
  1041  	// +PCQuantum because traceFrameForPC expects return PCs and subtracts PCQuantum.
  1042  	id := trace.stackTab.put([]uintptr{pc + sys.PCQuantum})
  1043  	traceEvent(traceEvGoCreate, 2, uint64(newg.goid), uint64(id))
  1044  }
  1045  
  1046  func traceGoStart() {
  1047  	_g_ := getg().m.curg
  1048  	_p_ := _g_.m.p
  1049  	_g_.traceseq++
  1050  	if _g_ == _p_.ptr().gcBgMarkWorker.ptr() {
  1051  		traceEvent(traceEvGoStartLabel, -1, uint64(_g_.goid), _g_.traceseq, trace.markWorkerLabels[_p_.ptr().gcMarkWorkerMode])
  1052  	} else if _g_.tracelastp == _p_ {
  1053  		traceEvent(traceEvGoStartLocal, -1, uint64(_g_.goid))
  1054  	} else {
  1055  		_g_.tracelastp = _p_
  1056  		traceEvent(traceEvGoStart, -1, uint64(_g_.goid), _g_.traceseq)
  1057  	}
  1058  }
  1059  
  1060  func traceGoEnd() {
  1061  	traceEvent(traceEvGoEnd, -1)
  1062  }
  1063  
  1064  func traceGoSched() {
  1065  	_g_ := getg()
  1066  	_g_.tracelastp = _g_.m.p
  1067  	traceEvent(traceEvGoSched, 1)
  1068  }
  1069  
  1070  func traceGoPreempt() {
  1071  	_g_ := getg()
  1072  	_g_.tracelastp = _g_.m.p
  1073  	traceEvent(traceEvGoPreempt, 1)
  1074  }
  1075  
  1076  func traceGoPark(traceEv byte, skip int) {
  1077  	if traceEv&traceFutileWakeup != 0 {
  1078  		traceEvent(traceEvFutileWakeup, -1)
  1079  	}
  1080  	traceEvent(traceEv & ^traceFutileWakeup, skip)
  1081  }
  1082  
  1083  func traceGoUnpark(gp *g, skip int) {
  1084  	_p_ := getg().m.p
  1085  	gp.traceseq++
  1086  	if gp.tracelastp == _p_ {
  1087  		traceEvent(traceEvGoUnblockLocal, skip, uint64(gp.goid))
  1088  	} else {
  1089  		gp.tracelastp = _p_
  1090  		traceEvent(traceEvGoUnblock, skip, uint64(gp.goid), gp.traceseq)
  1091  	}
  1092  }
  1093  
  1094  func traceGoSysCall() {
  1095  	traceEvent(traceEvGoSysCall, 1)
  1096  }
  1097  
  1098  func traceGoSysExit(ts int64) {
  1099  	if ts != 0 && ts < trace.ticksStart {
  1100  		// There is a race between the code that initializes sysexitticks
  1101  		// (in exitsyscall, which runs without a P, and therefore is not
  1102  		// stopped with the rest of the world) and the code that initializes
  1103  		// a new trace. The recorded sysexitticks must therefore be treated
  1104  		// as "best effort". If they are valid for this trace, then great,
  1105  		// use them for greater accuracy. But if they're not valid for this
  1106  		// trace, assume that the trace was started after the actual syscall
  1107  		// exit (but before we actually managed to start the goroutine,
  1108  		// aka right now), and assign a fresh time stamp to keep the log consistent.
  1109  		ts = 0
  1110  	}
  1111  	_g_ := getg().m.curg
  1112  	_g_.traceseq++
  1113  	_g_.tracelastp = _g_.m.p
  1114  	traceEvent(traceEvGoSysExit, -1, uint64(_g_.goid), _g_.traceseq, uint64(ts)/traceTickDiv)
  1115  }
  1116  
  1117  func traceGoSysBlock(pp *p) {
  1118  	// Sysmon and stopTheWorld can declare syscalls running on remote Ps as blocked,
  1119  	// to handle this we temporary employ the P.
  1120  	mp := acquirem()
  1121  	oldp := mp.p
  1122  	mp.p.set(pp)
  1123  	traceEvent(traceEvGoSysBlock, -1)
  1124  	mp.p = oldp
  1125  	releasem(mp)
  1126  }
  1127  
  1128  func traceHeapAlloc() {
  1129  	traceEvent(traceEvHeapAlloc, -1, memstats.heap_live)
  1130  }
  1131  
  1132  func traceNextGC() {
  1133  	if memstats.next_gc == ^uint64(0) {
  1134  		// Heap-based triggering is disabled.
  1135  		traceEvent(traceEvNextGC, -1, 0)
  1136  	} else {
  1137  		traceEvent(traceEvNextGC, -1, memstats.next_gc)
  1138  	}
  1139  }
  1140  
  1141  // To access runtime functions from runtime/trace.
  1142  // See runtime/trace/annotation.go
  1143  
  1144  //go:linkname trace_userTaskCreate runtime/trace.userTaskCreate
  1145  func trace_userTaskCreate(id, parentID uint64, taskType string) {
  1146  	if !trace.enabled {
  1147  		return
  1148  	}
  1149  
  1150  	// Same as in traceEvent.
  1151  	mp, pid, bufp := traceAcquireBuffer()
  1152  	if !trace.enabled && !mp.startingtrace {
  1153  		traceReleaseBuffer(pid)
  1154  		return
  1155  	}
  1156  
  1157  	typeStringID, bufp := traceString(bufp, pid, taskType)
  1158  	traceEventLocked(0, mp, pid, bufp, traceEvUserTaskCreate, 3, id, parentID, typeStringID)
  1159  	traceReleaseBuffer(pid)
  1160  }
  1161  
  1162  //go:linkname trace_userTaskEnd runtime/trace.userTaskEnd
  1163  func trace_userTaskEnd(id uint64) {
  1164  	traceEvent(traceEvUserTaskEnd, 2, id)
  1165  }
  1166  
  1167  //go:linkname trace_userRegion runtime/trace.userRegion
  1168  func trace_userRegion(id, mode uint64, name string) {
  1169  	if !trace.enabled {
  1170  		return
  1171  	}
  1172  
  1173  	mp, pid, bufp := traceAcquireBuffer()
  1174  	if !trace.enabled && !mp.startingtrace {
  1175  		traceReleaseBuffer(pid)
  1176  		return
  1177  	}
  1178  
  1179  	nameStringID, bufp := traceString(bufp, pid, name)
  1180  	traceEventLocked(0, mp, pid, bufp, traceEvUserRegion, 3, id, mode, nameStringID)
  1181  	traceReleaseBuffer(pid)
  1182  }
  1183  
  1184  //go:linkname trace_userLog runtime/trace.userLog
  1185  func trace_userLog(id uint64, category, message string) {
  1186  	if !trace.enabled {
  1187  		return
  1188  	}
  1189  
  1190  	mp, pid, bufp := traceAcquireBuffer()
  1191  	if !trace.enabled && !mp.startingtrace {
  1192  		traceReleaseBuffer(pid)
  1193  		return
  1194  	}
  1195  
  1196  	categoryID, bufp := traceString(bufp, pid, category)
  1197  
  1198  	extraSpace := traceBytesPerNumber + len(message) // extraSpace for the value string
  1199  	traceEventLocked(extraSpace, mp, pid, bufp, traceEvUserLog, 3, id, categoryID)
  1200  	// traceEventLocked reserved extra space for val and len(val)
  1201  	// in buf, so buf now has room for the following.
  1202  	buf := bufp.ptr()
  1203  
  1204  	// double-check the message and its length can fit.
  1205  	// Otherwise, truncate the message.
  1206  	slen := len(message)
  1207  	if room := len(buf.arr) - buf.pos; room < slen+traceBytesPerNumber {
  1208  		slen = room
  1209  	}
  1210  	buf.varint(uint64(slen))
  1211  	buf.pos += copy(buf.arr[buf.pos:], message[:slen])
  1212  
  1213  	traceReleaseBuffer(pid)
  1214  }
  1215  

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