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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>
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@ -312,9 +312,9 @@ func ReadMetricsSlow(memStats *MemStats, samplesp unsafe.Pointer, len, cap int)
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// Initialize the metrics beforehand because this could
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// allocate and skew the stats.
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semacquire(&metricsSema)
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metricsLock()
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initMetrics()
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semrelease(&metricsSema)
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metricsUnlock()
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systemstack(func() {
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// Read memstats first. It's going to flush
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@ -12,9 +12,12 @@ import (
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)
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var (
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// metrics is a map of runtime/metrics keys to
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// data used by the runtime to sample each metric's
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// value.
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// metrics is a map of runtime/metrics keys to data used by the runtime
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// to sample each metric's value. metricsInit indicates it has been
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// initialized.
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//
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// These fields are protected by metricsSema which should be
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// locked/unlocked with metricsLock() / metricsUnlock().
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metricsSema uint32 = 1
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metricsInit bool
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metrics map[string]metricData
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@ -34,6 +37,23 @@ type metricData struct {
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compute func(in *statAggregate, out *metricValue)
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}
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func metricsLock() {
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// Acquire the metricsSema but with handoff. Operations are typically
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// expensive enough that queueing up goroutines and handing off between
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// them will be noticeably better-behaved.
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semacquire1(&metricsSema, true, 0, 0)
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if raceenabled {
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raceacquire(unsafe.Pointer(&metricsSema))
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}
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}
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func metricsUnlock() {
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if raceenabled {
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racerelease(unsafe.Pointer(&metricsSema))
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}
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semrelease(&metricsSema)
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}
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// initMetrics initializes the metrics map if it hasn't been yet.
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//
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// metricsSema must be held.
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@ -570,10 +590,7 @@ func readMetrics(samplesp unsafe.Pointer, len int, cap int) {
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sl := slice{samplesp, len, cap}
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samples := *(*[]metricSample)(unsafe.Pointer(&sl))
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// Acquire the metricsSema but with handoff. This operation
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// is expensive enough that queueing up goroutines and handing
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// off between them will be noticeably better-behaved.
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semacquire1(&metricsSema, true, 0, 0)
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metricsLock()
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// Ensure the map is initialized.
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initMetrics()
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@ -597,5 +614,5 @@ func readMetrics(samplesp unsafe.Pointer, len int, cap int) {
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data.compute(&agg, &sample.value)
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}
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semrelease(&metricsSema)
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metricsUnlock()
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}
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