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-rw-r--r--src/runtime/proflabel.go40
1 files changed, 40 insertions, 0 deletions
diff --git a/src/runtime/proflabel.go b/src/runtime/proflabel.go
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+// 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
+}