diff options
Diffstat (limited to 'src/pkg/sync/waitgroup.go')
| -rw-r--r-- | src/pkg/sync/waitgroup.go | 39 |
1 files changed, 36 insertions, 3 deletions
diff --git a/src/pkg/sync/waitgroup.go b/src/pkg/sync/waitgroup.go index 0165b1ffb..1277f1c6d 100644 --- a/src/pkg/sync/waitgroup.go +++ b/src/pkg/sync/waitgroup.go @@ -4,7 +4,10 @@ package sync -import "sync/atomic" +import ( + "sync/atomic" + "unsafe" +) // A WaitGroup waits for a collection of goroutines to finish. // The main goroutine calls Add to set the number of @@ -31,11 +34,22 @@ type WaitGroup struct { // G3: Wait() // G1 still hasn't run, G3 finds sema == 1, unblocked! Bug. // Add adds delta, which may be negative, to the WaitGroup counter. -// If the counter becomes zero, all goroutines blocked on Wait() are released. +// If the counter becomes zero, all goroutines blocked on Wait are released. +// If the counter goes negative, Add panics. +// +// Note that calls with positive delta must happen before the call to Wait, +// or else Wait may wait for too small a group. Typically this means the calls +// to Add should execute before the statement creating the goroutine or +// other event to be waited for. See the WaitGroup example. func (wg *WaitGroup) Add(delta int) { + if raceenabled { + raceReleaseMerge(unsafe.Pointer(wg)) + raceDisable() + defer raceEnable() + } v := atomic.AddInt32(&wg.counter, int32(delta)) if v < 0 { - panic("sync: negative WaitGroup count") + panic("sync: negative WaitGroup counter") } if v > 0 || atomic.LoadInt32(&wg.waiters) == 0 { return @@ -56,7 +70,14 @@ func (wg *WaitGroup) Done() { // Wait blocks until the WaitGroup counter is zero. func (wg *WaitGroup) Wait() { + if raceenabled { + raceDisable() + } if atomic.LoadInt32(&wg.counter) == 0 { + if raceenabled { + raceEnable() + raceAcquire(unsafe.Pointer(wg)) + } return } wg.m.Lock() @@ -67,7 +88,15 @@ func (wg *WaitGroup) Wait() { // to avoid missing an Add. if atomic.LoadInt32(&wg.counter) == 0 { atomic.AddInt32(&wg.waiters, -1) + if raceenabled { + raceEnable() + raceAcquire(unsafe.Pointer(wg)) + raceDisable() + } wg.m.Unlock() + if raceenabled { + raceEnable() + } return } if wg.sema == nil { @@ -76,4 +105,8 @@ func (wg *WaitGroup) Wait() { s := wg.sema wg.m.Unlock() runtime_Semacquire(s) + if raceenabled { + raceEnable() + raceAcquire(unsafe.Pointer(wg)) + } } |