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Diffstat (limited to 'src/pkg/sync/cond.go')
-rw-r--r-- | src/pkg/sync/cond.go | 118 |
1 files changed, 0 insertions, 118 deletions
diff --git a/src/pkg/sync/cond.go b/src/pkg/sync/cond.go deleted file mode 100644 index 9e6bc170f..000000000 --- a/src/pkg/sync/cond.go +++ /dev/null @@ -1,118 +0,0 @@ -// 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 - -import ( - "sync/atomic" - "unsafe" -) - -// 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. -// -// A Cond can be created as part of other structures. -// A Cond must not be copied after first use. -type Cond struct { - // L is held while observing or changing the condition - L Locker - - sema syncSema - waiters uint32 // number of waiters - checker copyChecker -} - -// 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() { - c.checker.check() - if raceenabled { - raceDisable() - } - atomic.AddUint32(&c.waiters, 1) - if raceenabled { - raceEnable() - } - c.L.Unlock() - runtime_Syncsemacquire(&c.sema) - 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() { - c.signalImpl(false) -} - -// 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() { - c.signalImpl(true) -} - -func (c *Cond) signalImpl(all bool) { - c.checker.check() - if raceenabled { - raceDisable() - } - for { - old := atomic.LoadUint32(&c.waiters) - if old == 0 { - if raceenabled { - raceEnable() - } - return - } - new := old - 1 - if all { - new = 0 - } - if atomic.CompareAndSwapUint32(&c.waiters, old, new) { - if raceenabled { - raceEnable() - } - runtime_Syncsemrelease(&c.sema, old-new) - return - } - } -} - -// copyChecker holds back pointer to itself to detect object copying. -type copyChecker uintptr - -func (c *copyChecker) check() { - if uintptr(*c) != uintptr(unsafe.Pointer(c)) && - !atomic.CompareAndSwapUintptr((*uintptr)(c), 0, uintptr(unsafe.Pointer(c))) && - uintptr(*c) != uintptr(unsafe.Pointer(c)) { - panic("sync.Cond is copied") - } -} |