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author | Ian Lance Taylor <iant@golang.org> | 2022-09-07 01:14:31 +0000 |
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committer | Gopher Robot <gobot@golang.org> | 2022-09-07 13:22:04 +0000 |
commit | b53471a655f3928d2d0a851b1fb5f7ebb02adc76 (patch) | |
tree | 207757df456374f8ff08f85f37be1004c4850c81 /src/sync | |
parent | ed530dbd077c8dbf680fabb1fb10da5239099e25 (diff) | |
download | go-git-b53471a655f3928d2d0a851b1fb5f7ebb02adc76.tar.gz |
Revert "sync: convert Once.done to atomic type"
This reverts commit CL 427140.
Reason for revert: Comments say that done should be the first field.
Change-Id: Id131da064146b44e1182289546aeb877867e63cc
Reviewed-on: https://go-review.googlesource.com/c/go/+/428638
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Diffstat (limited to 'src/sync')
-rw-r--r-- | src/sync/once.go | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/src/sync/once.go b/src/sync/once.go index 587eab0af9..b6399cfc3d 100644 --- a/src/sync/once.go +++ b/src/sync/once.go @@ -16,13 +16,13 @@ import ( // the return from f “synchronizes before” // the return from any call of once.Do(f). type Once struct { - m Mutex // done indicates whether the action has been performed. // It is first in the struct because it is used in the hot path. // The hot path is inlined at every call site. // Placing done first allows more compact instructions on some architectures (amd64/386), // and fewer instructions (to calculate offset) on other architectures. - done atomic.Bool + done uint32 + m Mutex } // Do calls the function f if and only if Do is being called for the @@ -48,7 +48,7 @@ type Once struct { func (o *Once) Do(f func()) { // Note: Here is an incorrect implementation of Do: // - // if o.done.CompareAndSwap(false, true) { + // if atomic.CompareAndSwapUint32(&o.done, 0, 1) { // f() // } // @@ -58,9 +58,9 @@ func (o *Once) Do(f func()) { // call f, and the second would return immediately, without // waiting for the first's call to f to complete. // This is why the slow path falls back to a mutex, and why - // the o.done.Store must be delayed until after f returns. + // the atomic.StoreUint32 must be delayed until after f returns. - if !o.done.Load() { + if atomic.LoadUint32(&o.done) == 0 { // Outlined slow-path to allow inlining of the fast-path. o.doSlow(f) } @@ -69,8 +69,8 @@ func (o *Once) Do(f func()) { func (o *Once) doSlow(f func()) { o.m.Lock() defer o.m.Unlock() - if !o.done.Load() { - defer o.done.Store(true) + if o.done == 0 { + defer atomic.StoreUint32(&o.done, 1) f() } } |