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sync.once: document that Do cannot be invoked recursively.

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documentation change only.

R=rsc
CC=golang-dev
https://golang.org/cl/1964043
This commit is contained in:
Rob Pike 2010-08-12 12:59:37 +10:00
parent 8fcdc6a1e2
commit 32a81fa8bb
1 changed files with 4 additions and 1 deletions
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5
src/pkg/sync/once.go
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@ -13,7 +13,7 @@ type Once struct {
// Do calls the function f if and only if the method is being called for the // Do calls the function f if and only if the method is being called for the
// first time with this receiver. In other words, given // first time with this receiver. In other words, given
// var once Once // var once Once
// if once.Do(f) is called multiple times, only the first call will invoke f, // if Do(f) is called multiple times, only the first call will invoke f,
// even if f has a different value in each invocation. A new instance of // even if f has a different value in each invocation. A new instance of
// Once is required for each function to execute. // Once is required for each function to execute.
// //
@ -22,6 +22,9 @@ type Once struct {
// arguments to a function to be invoked by Do: // arguments to a function to be invoked by Do:
// config.once.Do(func() { config.init(filename) }) // config.once.Do(func() { config.init(filename) })
// //
// Because no call to Do returns until the one call to f returns, if f causes
// Do to be called, it will deadlock.
//
func (o *Once) Do(f func()) { func (o *Once) Do(f func()) {
o.m.Lock() o.m.Lock()
defer o.m.Unlock() defer o.m.Unlock()