runtime: add mayAcquire annotation for trace.lock

Now that we've moved the trace locks to the leaf of the lock graph, we
can safely annotate that any trace event may acquire trace.lock even
if dynamically it turns out a particular event doesn't need to flush
and acquire this lock.

This reveals a new edge where we can trace while holding the mheap
lock, so we add this to the lock graph.

For #53789.
Updates #53979.

Change-Id: I13e2f6cd1b621cca4bed0cc13ef12e64d05c89a7
Reviewed-on: https://go-review.googlesource.com/c/go/+/418720
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

diff --git a/src/runtime/lockrank.go b/src/runtime/lockrank.go
index ba4dd71c71f6850511668353148e8a8e495850d5..fbfef357708d8ee1be7333fb61c30d606e29abf2 100644 (file)
--- a/src/runtime/lockrank.go
+++ b/src/runtime/lockrank.go
@@ -174,8 +174,8 @@ var lockPartialOrder [][]lockRank = [][]lockRank{
        lockRankWbufSpans:     {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankGcBitsArenas, lockRankMspanSpecial, lockRankSpanSetSpine, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan},
        lockRankMheap:         {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRwmutexW, lockRankRwmutexR, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankGcBitsArenas, lockRankMspanSpecial, lockRankSpanSetSpine, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans},
        lockRankGlobalAlloc:   {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRwmutexW, lockRankRwmutexR, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankGcBitsArenas, lockRankMheapSpecial, lockRankMspanSpecial, lockRankSpanSetSpine, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap},
-       lockRankTrace:         {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankFin},
-       lockRankTraceStackTab: {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankTrace},
+       lockRankTrace:         {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRwmutexW, lockRankRwmutexR, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankGcBitsArenas, lockRankMspanSpecial, lockRankSpanSetSpine, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap},
+       lockRankTraceStackTab: {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRwmutexW, lockRankRwmutexR, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankGcBitsArenas, lockRankMspanSpecial, lockRankSpanSetSpine, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap, lockRankTrace},
        lockRankPanic:         {},
        lockRankDeadlock:      {lockRankPanic, lockRankDeadlock},
 }

diff --git a/src/runtime/mklockrank.go b/src/runtime/mklockrank.go
index 4445e8327e3d29b8e299649536d1ebe03208c8ca..9f269fd7b588fad2bfa324f82a13bbbd90c834d9 100644 (file)
--- a/src/runtime/mklockrank.go
+++ b/src/runtime/mklockrank.go
@@ -159,6 +159,7 @@ mheap, mheapSpecial < globalAlloc;
 
 # Execution tracer events (with a P)
 hchan,
+  mheap,
   root,
   sched,
   traceStrings,

diff --git a/src/runtime/trace.go b/src/runtime/trace.go
index 56fd1ba37b6361c99f6d67dbe7665ec242480c3c..4290d9224082404dcf66c181f8826bda06b69f93 100644 (file)
--- a/src/runtime/trace.go
+++ b/src/runtime/trace.go
@@ -883,6 +883,11 @@ func traceStackID(mp *m, buf []uintptr, skip int) uint64 {
 
 // traceAcquireBuffer returns trace buffer to use and, if necessary, locks it.
 func traceAcquireBuffer() (mp *m, pid int32, bufp *traceBufPtr) {
+       // Any time we acquire a buffer, we may end up flushing it,
+       // but flushes are rare. Record the lock edge even if it
+       // doesn't happen this time.
+       lockRankMayTraceFlush()
+
        mp = acquirem()
        if p := mp.p.ptr(); p != nil {
                return mp, p.id, &p.tracebuf
@@ -899,6 +904,16 @@ func traceReleaseBuffer(pid int32) {
        releasem(getg().m)
 }
 
+// lockRankMayTraceFlush records the lock ranking effects of a
+// potential call to traceFlush.
+func lockRankMayTraceFlush() {
+       owner := trace.lockOwner
+       dolock := owner == nil || owner != getg().m.curg
+       if dolock {
+               lockWithRankMayAcquire(&trace.lock, getLockRank(&trace.lock))
+       }
+}
+
 // traceFlush puts buf onto stack of full buffers and returns an empty buffer.
 //
 // This must run on the system stack because it acquires trace.lock.