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runtime: record mutex event before readying
Currently, semrelease1 readies the next waiter before recording a mutex event. However, if the next waiter is expecting to look at the mutex profile, as is the case in TestMutexProfile, this may delay recording the event too much. Swap the order of these operations so semrelease1 records the mutex event before readying the next waiter. This also means readying the next waiter is the very last thing semrelease1 does, which seems appropriate. Fixes #19139. Change-Id: I1a62063599fdb5d49bd86061a180c0a2d659474b Reviewed-on: https://go-review.googlesource.com/45751 Run-TryBot: Austin Clements <austin@google.com> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org> Reviewed-by: Peter Weinberger <pjw@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org>
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@ -542,6 +542,10 @@ func blockMutex() {
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time.Sleep(blockDelay)
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time.Sleep(blockDelay)
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mu.Unlock()
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mu.Unlock()
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}()
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}()
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// Note: Unlock releases mu before recording the mutex event,
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// so it's theoretically possible for this to proceed and
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// capture the profile before the event is recorded. As long
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// as this is blocked before the unlock happens, it's okay.
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mu.Lock()
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mu.Lock()
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}
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}
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@ -560,7 +564,6 @@ func blockCond() {
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}
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}
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func TestMutexProfile(t *testing.T) {
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func TestMutexProfile(t *testing.T) {
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testenv.SkipFlaky(t, 19139)
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old := runtime.SetMutexProfileFraction(1)
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old := runtime.SetMutexProfileFraction(1)
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defer runtime.SetMutexProfileFraction(old)
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defer runtime.SetMutexProfileFraction(old)
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if old != 0 {
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if old != 0 {
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@ -182,6 +182,9 @@ func semrelease1(addr *uint32, handoff bool) {
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unlock(&root.lock)
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unlock(&root.lock)
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if s != nil { // May be slow, so unlock first
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if s != nil { // May be slow, so unlock first
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acquiretime := s.acquiretime
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acquiretime := s.acquiretime
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if acquiretime != 0 {
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mutexevent(t0-acquiretime, 3)
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}
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if s.ticket != 0 {
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if s.ticket != 0 {
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throw("corrupted semaphore ticket")
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throw("corrupted semaphore ticket")
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}
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}
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@ -189,9 +192,6 @@ func semrelease1(addr *uint32, handoff bool) {
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s.ticket = 1
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s.ticket = 1
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}
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}
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readyWithTime(s, 5)
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readyWithTime(s, 5)
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if acquiretime != 0 {
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mutexevent(t0-acquiretime, 3)
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}
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}
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}
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}
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}
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