runtime: add race annotations to metricsSema
metricsSema protects the metrics map. The map implementation is race
instrumented regardless of which package is it called from.
semacquire/semrelease are not automatically race instrumented, so we can
trigger race false positives without manually annotating our lock
acquire and release.
See similar instrumentation on trace.shutdownSema and reflectOffs.lock.
Fixes #53542.
Change-Id: Ia3fd239ac860e037d09c7cb9c4ad267391e70705
Reviewed-on: https://go-review.googlesource.com/c/go/+/414517
Run-TryBot: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
diff --git a/src/runtime/export_test.go b/src/runtime/export_test.go
index 1626f99..9639946 100644
--- a/src/runtime/export_test.go
+++ b/src/runtime/export_test.go
@@ -312,9 +312,9 @@
// Initialize the metrics beforehand because this could
// allocate and skew the stats.
- semacquire(&metricsSema)
+ metricsLock()
initMetrics()
- semrelease(&metricsSema)
+ metricsUnlock()
systemstack(func() {
// Read memstats first. It's going to flush
diff --git a/src/runtime/metrics.go b/src/runtime/metrics.go
index 75ad318..986121b 100644
--- a/src/runtime/metrics.go
+++ b/src/runtime/metrics.go
@@ -12,9 +12,12 @@
)
var (
- // metrics is a map of runtime/metrics keys to
- // data used by the runtime to sample each metric's
- // value.
+ // metrics is a map of runtime/metrics keys to data used by the runtime
+ // to sample each metric's value. metricsInit indicates it has been
+ // initialized.
+ //
+ // These fields are protected by metricsSema which should be
+ // locked/unlocked with metricsLock() / metricsUnlock().
metricsSema uint32 = 1
metricsInit bool
metrics map[string]metricData
@@ -34,6 +37,23 @@
compute func(in *statAggregate, out *metricValue)
}
+func metricsLock() {
+ // Acquire the metricsSema but with handoff. Operations are typically
+ // expensive enough that queueing up goroutines and handing off between
+ // them will be noticeably better-behaved.
+ semacquire1(&metricsSema, true, 0, 0)
+ if raceenabled {
+ raceacquire(unsafe.Pointer(&metricsSema))
+ }
+}
+
+func metricsUnlock() {
+ if raceenabled {
+ racerelease(unsafe.Pointer(&metricsSema))
+ }
+ semrelease(&metricsSema)
+}
+
// initMetrics initializes the metrics map if it hasn't been yet.
//
// metricsSema must be held.
@@ -570,10 +590,7 @@
sl := slice{samplesp, len, cap}
samples := *(*[]metricSample)(unsafe.Pointer(&sl))
- // Acquire the metricsSema but with handoff. This operation
- // is expensive enough that queueing up goroutines and handing
- // off between them will be noticeably better-behaved.
- semacquire1(&metricsSema, true, 0, 0)
+ metricsLock()
// Ensure the map is initialized.
initMetrics()
@@ -597,5 +614,5 @@
data.compute(&agg, &sample.value)
}
- semrelease(&metricsSema)
+ metricsUnlock()
}