Adding upstream version 1.21.8.upstream/1.21.8

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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
+}