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runtime: add race annotations to metricsSema

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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>
This commit is contained in:
Michael Pratt 2022-06-28 15:17:12 -04:00 committed by David Chase
parent bd1783e812
commit d6481d5b96
2 changed files with 27 additions and 10 deletions
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4
src/runtime/export_test.go
View File

@ -312,9 +312,9 @@ func ReadMetricsSlow(memStats *MemStats, samplesp unsafe.Pointer, len, cap int)
// 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

33
src/runtime/metrics.go
View File

@ -12,9 +12,12 @@ import (
)
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 @@ type metricData struct {
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 @@ func readMetrics(samplesp unsafe.Pointer, len int, cap int) {
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 @@ func readMetrics(samplesp unsafe.Pointer, len int, cap int) {
data.compute(&agg, &sample.value)
}
semrelease(&metricsSema)
metricsUnlock()
}