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sync: be more explicit in WaitGroup docs

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Fixes #8543.

LGTM=dvyukov, r
R=rsc, r
CC=dvyukov, golang-codereviews
https://golang.org/cl/123580043
This commit is contained in:
Andrew Gerrand 2014-08-22 09:53:44 +10:00
parent f129370b3e
commit bc64c07825
1 changed files with 7 additions and 4 deletions
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11
src/pkg/sync/waitgroup.go
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@ -37,10 +37,13 @@ type WaitGroup struct {
// 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.
// Note that calls with a positive delta that occur when the counter is zero
// must happen before a Wait. Calls with a negative delta, or calls with a
// positive delta that start when the counter is greater than zero, may happen
// at any time.
// 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 {
_ = wg.m.state // trigger nil deref early