[release-branch.go1.9] runtime: in cpuProfile.addExtra, set p.lostExtra to 0 after...

After the number of lost extra events are written to the the cpuprof log,
the number of lost extra events should be set to zero, or else, the next
time time addExtra is logged, lostExtra will be overcounted. This change
resets lostExtra after its value is written to the log.

Fixes #21836

Change-Id: I8a6ac9c61e579e7a5ca7bdb0f3463f8ae8b9f864
Reviewed-on: https://go-review.googlesource.com/63270
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-on: https://go-review.googlesource.com/70974
Run-TryBot: Russ Cox <rsc@golang.org>

diff --git a/src/runtime/cpuprof.go b/src/runtime/cpuprof.go
index fb841a9f3ddcb12191a009c1cd3b703cc114cf38..e00dcb1bbd2ef45586c146d5b632216351407c16 100644 (file)
--- a/src/runtime/cpuprof.go
+++ b/src/runtime/cpuprof.go
@@ -160,6 +160,7 @@ func (p *cpuProfile) addExtra() {
                        funcPC(_ExternalCode) + sys.PCQuantum,
                }
                cpuprof.log.write(nil, 0, hdr[:], lostStk[:])
+               p.lostExtra = 0
        }
 }