runtime/pprof: fix data race between Profile.Add and Profile.WriteTo
p.m is accessed in WriteTo without holding p.mu.
Move the access inside the critical section.
The race detector catches this bug using this program:
package main
import (
"os"
"runtime/pprof"
"time"
)
func main() {
p := pprof.NewProfile("ABC")
go func() {
p.WriteTo(os.Stdout, 1)
time.Sleep(time.Second)
}()
p.Add("abc", 0)
time.Sleep(time.Second)
}
$ go run -race x.go
==================
WARNING: DATA RACE
Write at 0x00c42007c240 by main goroutine:
runtime.mapassign()
/Users/josh/go/tip/src/runtime/hashmap.go:485 +0x0
runtime/pprof.(*Profile).Add()
/Users/josh/go/tip/src/runtime/pprof/pprof.go:281 +0x255
main.main()
/Users/josh/go/tip/src/p.go:15 +0x9d
Previous read at 0x00c42007c240 by goroutine 6:
runtime/pprof.(*Profile).WriteTo()
/Users/josh/go/tip/src/runtime/pprof/pprof.go:314 +0xc5
main.main.func1()
/Users/josh/go/tip/src/x.go:12 +0x69
Goroutine 6 (running) created at:
main.main()
/Users/josh/go/tip/src/x.go:11 +0x6e
==================
ABC profile: total 1
1 @ 0x110ccb4 0x111aeee 0x1055053 0x107f031