diff options
Diffstat (limited to 'pkg/sync/seqcount.go')
| -rw-r--r-- | pkg/sync/seqcount.go | 30 |
1 files changed, 20 insertions, 10 deletions
diff --git a/pkg/sync/seqcount.go b/pkg/sync/seqcount.go index a1e895352..2c5d3df99 100644 --- a/pkg/sync/seqcount.go +++ b/pkg/sync/seqcount.go @@ -8,7 +8,6 @@ package sync import ( "fmt" "reflect" - "runtime" "sync/atomic" ) @@ -43,9 +42,7 @@ type SeqCount struct { } // SeqCountEpoch tracks writer critical sections in a SeqCount. -type SeqCountEpoch struct { - val uint32 -} +type SeqCountEpoch uint32 // We assume that: // @@ -83,12 +80,25 @@ type SeqCountEpoch struct { // using this pattern. Most users of SeqCount will need to use the // SeqAtomicLoad function template in seqatomic.go. func (s *SeqCount) BeginRead() SeqCountEpoch { - epoch := atomic.LoadUint32(&s.epoch) - for epoch&1 != 0 { - runtime.Gosched() - epoch = atomic.LoadUint32(&s.epoch) + if epoch := atomic.LoadUint32(&s.epoch); epoch&1 == 0 { + return SeqCountEpoch(epoch) + } + return s.beginReadSlow() +} + +func (s *SeqCount) beginReadSlow() SeqCountEpoch { + i := 0 + for { + if canSpin(i) { + i++ + doSpin() + } else { + goyield() + } + if epoch := atomic.LoadUint32(&s.epoch); epoch&1 == 0 { + return SeqCountEpoch(epoch) + } } - return SeqCountEpoch{epoch} } // ReadOk returns true if the reader critical section initiated by a previous @@ -99,7 +109,7 @@ func (s *SeqCount) BeginRead() SeqCountEpoch { // Reader critical sections do not need to be explicitly terminated; the last // call to ReadOk is implicitly the end of the reader critical section. func (s *SeqCount) ReadOk(epoch SeqCountEpoch) bool { - return atomic.LoadUint32(&s.epoch) == epoch.val + return atomic.LoadUint32(&s.epoch) == uint32(epoch) } // BeginWrite indicates the beginning of a writer critical section. |