diff options
Diffstat (limited to 'src/runtime/proflabel.go')
| -rw-r--r-- | src/runtime/proflabel.go | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/src/runtime/proflabel.go b/src/runtime/proflabel.go new file mode 100644 index 0000000..b2a1617 --- /dev/null +++ b/src/runtime/proflabel.go @@ -0,0 +1,40 @@ +// Copyright 2017 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package runtime + +import "unsafe" + +var labelSync uintptr + +//go:linkname runtime_setProfLabel runtime/pprof.runtime_setProfLabel +func runtime_setProfLabel(labels unsafe.Pointer) { + // Introduce race edge for read-back via profile. + // This would more properly use &getg().labels as the sync address, + // but we do the read in a signal handler and can't call the race runtime then. + // + // This uses racereleasemerge rather than just racerelease so + // the acquire in profBuf.read synchronizes with *all* prior + // setProfLabel operations, not just the most recent one. This + // is important because profBuf.read will observe different + // labels set by different setProfLabel operations on + // different goroutines, so it needs to synchronize with all + // of them (this wouldn't be an issue if we could synchronize + // on &getg().labels since we would synchronize with each + // most-recent labels write separately.) + // + // racereleasemerge is like a full read-modify-write on + // labelSync, rather than just a store-release, so it carries + // a dependency on the previous racereleasemerge, which + // ultimately carries forward to the acquire in profBuf.read. + if raceenabled { + racereleasemerge(unsafe.Pointer(&labelSync)) + } + getg().labels = labels +} + +//go:linkname runtime_getProfLabel runtime/pprof.runtime_getProfLabel +func runtime_getProfLabel() unsafe.Pointer { + return getg().labels +} |