runtime: goroutines that stop after calling runtime.RaceDisable break race detector #60934
Description
What version of Go are you using (go version)?
$ go version go version go1.20.5 darwin/arm64
Does this issue reproduce with the latest release?
Yes, reproduces on tip.
What operating system and processor architecture are you using (go env)?
go env Output
$ go env GO111MODULE="" GOARCH="arm64" GOBIN="" GOCACHE="/Users/jelle/Library/Caches/go-build" GOENV="/Users/jelle/Library/Application Support/go/env" GOEXE="" GOEXPERIMENT="" GOFLAGS="" GOHOSTARCH="arm64" GOHOSTOS="darwin" GOINSECURE="" GOMODCACHE="/Users/jelle/go/pkg/mod" GONOPROXY="" GONOSUMDB="" GOOS="darwin" GOPATH="/Users/jelle/go" GOPRIVATE="" GOPROXY="https://proxy.golang.org,direct" GOROOT="/opt/homebrew/Cellar/go/1.20.5/libexec" GOSUMDB="sum.golang.org" GOTMPDIR="" GOTOOLDIR="/opt/homebrew/Cellar/go/1.20.5/libexec/pkg/tool/darwin_arm64" GOVCS="" GOVERSION="go1.20.5" GCCGO="gccgo" AR="ar" CC="cc" CXX="c++" CGO_ENABLED="1" GOMOD="/dev/null" GOWORK="" CGO_CFLAGS="-O2 -g" CGO_CPPFLAGS="" CGO_CXXFLAGS="-O2 -g" CGO_FFLAGS="-O2 -g" CGO_LDFLAGS="-O2 -g" PKG_CONFIG="pkg-config" GOGCCFLAGS="-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/rr/r3bbgb153sq467ngl1m0q3z00000gn/T/go-build2978985759=/tmp/go-build -gno-record-gcc-switches -fno-common"
What did you do?
I am using the race detector in a rather tricky setting: I call runtime.RaceDisable and runtime.RaceEnable to have the race detector ignore certain happens-before edges. If a goroutine stops after calling runtime.RaceDisable, but before calling runtime.RaceEnable because it panics, the race detector is broken afterwards.
Calling runtime.RaceDisable causes problems because it tracks state in a per-g field g.raceignore that does not get reset when the g is reused by a later new goroutine.
This program reproduces the issue:
package main
import (
"fmt"
"runtime"
"time"
)
func main() {
// create several gs that have mismatched RaceDisable/RaceEnable
for i := 0; i < 100; i++ {
go func() {
// make sure gs run in parallel by sleeping
time.Sleep(10 * time.Millisecond)
runtime.RaceDisable()
}()
}
// wait for all gs above to finish
time.Sleep(20 * time.Millisecond)
// shared variable protected by reading/writing ch
var x int
ch := make(chan struct{}, 0)
go func() {
x = 1
ch <- struct{}{}
}()
go func() {
<-ch
_ = x
}()
time.Sleep(20 * time.Millisecond)
fmt.Println("done")
}What did you expect to see?
$ go run -race .
done
What did you see instead?
$ go run -race .
==================
WARNING: DATA RACE
Read at 0x00c0000ba008 by goroutine 110:
main.main.func3()
/Users/jelle/hack/go-bugs/raceenable/main.go:33 +0x40
Previous write at 0x00c0000ba008 by goroutine 109:
main.main.func2()
/Users/jelle/hack/go-bugs/raceenable/main.go:28 +0x34
Goroutine 110 (running) created at:
main.main()
/Users/jelle/hack/go-bugs/raceenable/main.go:31 +0x1c4
Goroutine 109 (finished) created at:
main.main()
/Users/jelle/hack/go-bugs/raceenable/main.go:27 +0x124
==================
done
Found 1 data race(s)
exit status 66