Closed
Description
Go version
go1.23.1
What did you do?
Print the stack traces of a runtime.MutexProfile() using the code below.
package main
import (
"fmt"
"runtime"
"sync"
"time"
)
func main() {
produceMutexContention()
printMutexProfile()
}
func produceMutexContention() {
runtime.SetMutexProfileFraction(1)
var mu sync.Mutex
done := make(chan struct{})
defer close(done)
for range runtime.GOMAXPROCS(-1) * 2 {
go func() {
for finish := false; !finish; {
mu.Lock()
select {
case <-done:
finish = true
default:
time.Sleep(time.Millisecond)
}
mu.Unlock()
}
}()
}
time.Sleep(time.Second)
}
func printMutexProfile() {
var records []runtime.BlockProfileRecord
for {
n, ok := runtime.MutexProfile(records)
if ok {
records = records[:n]
break
}
records = make([]runtime.BlockProfileRecord, n*2)
}
for _, r := range records {
var funcs []string
frames := runtime.CallersFrames(r.Stack())
for {
frame, more := frames.Next()
funcs = append(funcs, frame.Function)
if !more {
break
}
}
fmt.Printf("%#v\n", funcs)
}
}What did you see happen?
go1.23.1 produces the following output:
[]string{"sync.(*Mutex).Unlock", "main.produceMutexContention.func1"}
[]string{""}
What did you expect to see?
The same output as go1.22.7:
[]string{"sync.(*Mutex).Unlock", "main.produceMutexContention.func1", "runtime.goexit"}
[]string{"runtime._LostContendedRuntimeLock"}
Additional Notes
This problem only happens when using the runtime.MutexProfile API. runtime/pprof output is not impacted.
I have submitted https://go-review.googlesource.com/c/go/+/611615 to fix this problem.
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