diff options
Diffstat (limited to 'src/runtime/trace.go')
| -rw-r--r-- | src/runtime/trace.go | 45 |
1 files changed, 38 insertions, 7 deletions
diff --git a/src/runtime/trace.go b/src/runtime/trace.go index 8cd95893a0..c81846221a 100644 --- a/src/runtime/trace.go +++ b/src/runtime/trace.go @@ -95,6 +95,7 @@ var trace struct { headerWritten bool // whether ReadTrace has emitted trace header footerWritten bool // whether ReadTrace has emitted trace footer shutdownSema uint32 // used to wait for ReadTrace completion + seqStart uint64 // sequence number when tracing was started ticksStart int64 // cputicks when tracing was started ticksEnd int64 // cputicks when tracing was stopped timeStart int64 // nanotime when tracing was started @@ -110,9 +111,31 @@ var trace struct { buf *traceBuf // global trace buffer, used when running without a p } +var traceseq uint64 // global trace sequence number + +// tracestamp returns a consistent sequence number, time stamp pair +// for use in a trace. We need to make sure that time stamp ordering +// (assuming synchronized CPUs) and sequence ordering match. +// To do that, we increment traceseq, grab ticks, and increment traceseq again. +// We treat odd traceseq as a sign that another thread is in the middle +// of the sequence and spin until it is done. +// Not splitting stack to avoid preemption, just in case the call sites +// that used to call xadd64 and cputicks are sensitive to that. +//go:nosplit +func tracestamp() (seq uint64, ts int64) { + seq = atomicload64(&traceseq) + for seq&1 != 0 || !cas64(&traceseq, seq, seq+1) { + seq = atomicload64(&traceseq) + } + ts = cputicks() + atomicstore64(&traceseq, seq+2) + return seq >> 1, ts +} + // traceBufHeader is per-P tracing buffer. type traceBufHeader struct { link *traceBuf // in trace.empty/full + lastSeq uint64 // sequence number of last event lastTicks uint64 // when we wrote the last event buf []byte // trace data, always points to traceBuf.arr stk [traceStackSize]uintptr // scratch buffer for traceback @@ -147,7 +170,7 @@ func StartTrace() error { return errorString("tracing is already enabled") } - trace.ticksStart = cputicks() + trace.seqStart, trace.ticksStart = tracestamp() trace.timeStart = nanotime() trace.headerWritten = false trace.footerWritten = false @@ -308,7 +331,7 @@ func ReadTrace() []byte { trace.headerWritten = true trace.lockOwner = nil unlock(&trace.lock) - return []byte("gotrace\x00") + return []byte("go 1.5 trace\x00\x00\x00\x00") } // Wait for new data. if trace.fullHead == nil && !trace.shutdown { @@ -334,9 +357,11 @@ func ReadTrace() []byte { var data []byte data = append(data, traceEvFrequency|0<<traceArgCountShift) data = traceAppend(data, uint64(freq)) + data = traceAppend(data, 0) if timers.gp != nil { data = append(data, traceEvTimerGoroutine|0<<traceArgCountShift) data = traceAppend(data, uint64(timers.gp.goid)) + data = traceAppend(data, 0) } return data } @@ -435,22 +460,27 @@ func traceEvent(ev byte, skip int, args ...uint64) { return } buf := *bufp - const maxSize = 2 + 4*traceBytesPerNumber // event type, length, timestamp, stack id and two add params + const maxSize = 2 + 5*traceBytesPerNumber // event type, length, sequence, timestamp, stack id and two add params if buf == nil || cap(buf.buf)-len(buf.buf) < maxSize { buf = traceFlush(buf) *bufp = buf } - ticks := uint64(cputicks()) / traceTickDiv + seq, ticksraw := tracestamp() + seqDiff := seq - buf.lastSeq + ticks := uint64(ticksraw) / traceTickDiv tickDiff := ticks - buf.lastTicks if len(buf.buf) == 0 { data := buf.buf data = append(data, traceEvBatch|1<<traceArgCountShift) data = traceAppend(data, uint64(pid)) + data = traceAppend(data, seq) data = traceAppend(data, ticks) buf.buf = data + seqDiff = 0 tickDiff = 0 } + buf.lastSeq = seq buf.lastTicks = ticks narg := byte(len(args)) if skip >= 0 { @@ -469,6 +499,7 @@ func traceEvent(ev byte, skip int, args ...uint64) { data = append(data, 0) lenp = &data[len(data)-1] } + data = traceAppend(data, seqDiff) data = traceAppend(data, tickDiff) for _, a := range args { data = traceAppend(data, a) @@ -800,12 +831,12 @@ func traceGoSysCall() { traceEvent(traceEvGoSysCall, 4) } -func traceGoSysExit(ts int64) { - if ts != 0 && ts < trace.ticksStart { +func traceGoSysExit(seq uint64, ts int64) { + if int64(seq)-int64(trace.seqStart) < 0 { // The timestamp was obtained during a previous tracing session, ignore. return } - traceEvent(traceEvGoSysExit, -1, uint64(getg().m.curg.goid), uint64(ts)/traceTickDiv) + traceEvent(traceEvGoSysExit, -1, uint64(getg().m.curg.goid), seq, uint64(ts)/traceTickDiv) } func traceGoSysBlock(pp *p) { |