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Add sync.SeqCount.BeginWriteOk.

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PiperOrigin-RevId: 430268914
This commit is contained in:
Jamie Liu
2022-02-22 12:25:20 -08:00
committed by gVisor bot
parent 6e5b602ee1
commit 377cfd813d
1 changed files with 11 additions and 1 deletions
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pkg/sync/seqcount.go
+11 -1
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@@ -117,7 +117,17 @@ func (s *SeqCount) BeginWrite() {
}
}
// EndWrite ends the effect of a preceding BeginWrite.
// BeginWriteOk combines the semantics of ReadOk and BeginWrite. If the reader
// critical section initiated by a previous call to BeginRead() that returned
// epoch did not race with any writer critical sections, it begins a writer
// critical section and returns true. Otherwise it does nothing and returns
// false.
func (s *SeqCount) BeginWriteOk(epoch SeqCountEpoch) bool {
return atomic.CompareAndSwapUint32(&s.epoch, uint32(epoch), uint32(epoch)+1)
}
// EndWrite ends the effect of a preceding BeginWrite or successful
// BeginWriteOk.
func (s *SeqCount) EndWrite() {
if epoch := atomic.AddUint32(&s.epoch, 1); epoch&1 != 0 {
panic("SeqCount.EndWrite outside writer critical section")