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-rw-r--r--gcc-4.8.1/libgo/go/sync/cond.go130
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diff --git a/gcc-4.8.1/libgo/go/sync/cond.go b/gcc-4.8.1/libgo/go/sync/cond.go
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--- a/gcc-4.8.1/libgo/go/sync/cond.go
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-// Copyright 2011 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package sync
-
-// Cond implements a condition variable, a rendezvous point
-// for goroutines waiting for or announcing the occurrence
-// of an event.
-//
-// Each Cond has an associated Locker L (often a *Mutex or *RWMutex),
-// which must be held when changing the condition and
-// when calling the Wait method.
-type Cond struct {
- L Locker // held while observing or changing the condition
- m Mutex // held to avoid internal races
-
- // We must be careful to make sure that when Signal
- // releases a semaphore, the corresponding acquire is
- // executed by a goroutine that was already waiting at
- // the time of the call to Signal, not one that arrived later.
- // To ensure this, we segment waiting goroutines into
- // generations punctuated by calls to Signal. Each call to
- // Signal begins another generation if there are no goroutines
- // left in older generations for it to wake. Because of this
- // optimization (only begin another generation if there
- // are no older goroutines left), we only need to keep track
- // of the two most recent generations, which we call old
- // and new.
- oldWaiters int // number of waiters in old generation...
- oldSema *uint32 // ... waiting on this semaphore
-
- newWaiters int // number of waiters in new generation...
- newSema *uint32 // ... waiting on this semaphore
-}
-
-// NewCond returns a new Cond with Locker l.
-func NewCond(l Locker) *Cond {
- return &Cond{L: l}
-}
-
-// Wait atomically unlocks c.L and suspends execution
-// of the calling goroutine. After later resuming execution,
-// Wait locks c.L before returning. Unlike in other systems,
-// Wait cannot return unless awoken by Broadcast or Signal.
-//
-// Because c.L is not locked when Wait first resumes, the caller
-// typically cannot assume that the condition is true when
-// Wait returns. Instead, the caller should Wait in a loop:
-//
-// c.L.Lock()
-// for !condition() {
-// c.Wait()
-// }
-// ... make use of condition ...
-// c.L.Unlock()
-//
-func (c *Cond) Wait() {
- if raceenabled {
- raceDisable()
- }
- c.m.Lock()
- if c.newSema == nil {
- c.newSema = new(uint32)
- }
- s := c.newSema
- c.newWaiters++
- c.m.Unlock()
- if raceenabled {
- raceEnable()
- }
- c.L.Unlock()
- runtime_Semacquire(s)
- c.L.Lock()
-}
-
-// Signal wakes one goroutine waiting on c, if there is any.
-//
-// It is allowed but not required for the caller to hold c.L
-// during the call.
-func (c *Cond) Signal() {
- if raceenabled {
- raceDisable()
- }
- c.m.Lock()
- if c.oldWaiters == 0 && c.newWaiters > 0 {
- // Retire old generation; rename new to old.
- c.oldWaiters = c.newWaiters
- c.oldSema = c.newSema
- c.newWaiters = 0
- c.newSema = nil
- }
- if c.oldWaiters > 0 {
- c.oldWaiters--
- runtime_Semrelease(c.oldSema)
- }
- c.m.Unlock()
- if raceenabled {
- raceEnable()
- }
-}
-
-// Broadcast wakes all goroutines waiting on c.
-//
-// It is allowed but not required for the caller to hold c.L
-// during the call.
-func (c *Cond) Broadcast() {
- if raceenabled {
- raceDisable()
- }
- c.m.Lock()
- // Wake both generations.
- if c.oldWaiters > 0 {
- for i := 0; i < c.oldWaiters; i++ {
- runtime_Semrelease(c.oldSema)
- }
- c.oldWaiters = 0
- }
- if c.newWaiters > 0 {
- for i := 0; i < c.newWaiters; i++ {
- runtime_Semrelease(c.newSema)
- }
- c.newWaiters = 0
- c.newSema = nil
- }
- c.m.Unlock()
- if raceenabled {
- raceEnable()
- }
-}