diff options
| -rw-r--r-- | src/context/benchmark_test.go | 20 | ||||
| -rw-r--r-- | src/context/context.go | 21 |
2 files changed, 31 insertions, 10 deletions
diff --git a/src/context/benchmark_test.go b/src/context/benchmark_test.go index 144f473a44..d10950d258 100644 --- a/src/context/benchmark_test.go +++ b/src/context/benchmark_test.go @@ -188,3 +188,23 @@ func BenchmarkDeepValueSameGoRoutine(b *testing.B) { }) } } + +func BenchmarkErrOK(b *testing.B) { + ctx, cancel := WithCancel(Background()) + defer cancel() + for b.Loop() { + if err := ctx.Err(); err != nil { + b.Fatalf("ctx.Err() = %v", err) + } + } +} + +func BenchmarkErrCanceled(b *testing.B) { + ctx, cancel := WithCancel(Background()) + cancel() + for b.Loop() { + if err := ctx.Err(); err == nil { + b.Fatalf("ctx.Err() = %v", err) + } + } +} diff --git a/src/context/context.go b/src/context/context.go index bef9e8aab0..6020e2d310 100644 --- a/src/context/context.go +++ b/src/context/context.go @@ -428,7 +428,7 @@ type cancelCtx struct { mu sync.Mutex // protects following fields done atomic.Value // of chan struct{}, created lazily, closed by first cancel call children map[canceler]struct{} // set to nil by the first cancel call - err error // set to non-nil by the first cancel call + err atomic.Value // set to non-nil by the first cancel call cause error // set to non-nil by the first cancel call } @@ -455,10 +455,11 @@ func (c *cancelCtx) Done() <-chan struct{} { } func (c *cancelCtx) Err() error { - c.mu.Lock() - err := c.err - c.mu.Unlock() - return err + // An atomic load is ~5x faster than a mutex, which can matter in tight loops. + if err := c.err.Load(); err != nil { + return err.(error) + } + return nil } // propagateCancel arranges for child to be canceled when parent is. @@ -482,9 +483,9 @@ func (c *cancelCtx) propagateCancel(parent Context, child canceler) { if p, ok := parentCancelCtx(parent); ok { // parent is a *cancelCtx, or derives from one. p.mu.Lock() - if p.err != nil { + if err := p.err.Load(); err != nil { // parent has already been canceled - child.cancel(false, p.err, p.cause) + child.cancel(false, err.(error), p.cause) } else { if p.children == nil { p.children = make(map[canceler]struct{}) @@ -545,11 +546,11 @@ func (c *cancelCtx) cancel(removeFromParent bool, err, cause error) { cause = err } c.mu.Lock() - if c.err != nil { + if c.err.Load() != nil { c.mu.Unlock() return // already canceled } - c.err = err + c.err.Store(err) c.cause = cause d, _ := c.done.Load().(chan struct{}) if d == nil { @@ -639,7 +640,7 @@ func WithDeadlineCause(parent Context, d time.Time, cause error) (Context, Cance } c.mu.Lock() defer c.mu.Unlock() - if c.err == nil { + if c.err.Load() == nil { c.timer = time.AfterFunc(dur, func() { c.cancel(true, DeadlineExceeded, cause) }) |