Move CancellationFlag and WaitableEvent to the synchronization subdirectory....

base/waitable_event_posix.cc

Index: base/waitable_event_posix.cc
===================================================================
--- base/waitable_event_posix.cc	(revision 70364)
+++ base/waitable_event_posix.cc	(working copy)
@@ -1,404 +0,0 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "base/waitable_event.h"
-
-#include "base/synchronization/condition_variable.h"
-#include "base/synchronization/lock.h"
-#include "base/message_loop.h"
-
-// -----------------------------------------------------------------------------
-// A WaitableEvent on POSIX is implemented as a wait-list. Currently we don't
-// support cross-process events (where one process can signal an event which
-// others are waiting on). Because of this, we can avoid having one thread per
-// listener in several cases.
-//
-// The WaitableEvent maintains a list of waiters, protected by a lock. Each
-// waiter is either an async wait, in which case we have a Task and the
-// MessageLoop to run it on, or a blocking wait, in which case we have the
-// condition variable to signal.
-//
-// Waiting involves grabbing the lock and adding oneself to the wait list. Async
-// waits can be canceled, which means grabbing the lock and removing oneself
-// from the list.
-//
-// Waiting on multiple events is handled by adding a single, synchronous wait to
-// the wait-list of many events. An event passes a pointer to itself when
-// firing a waiter and so we can store that pointer to find out which event
-// triggered.
-// -----------------------------------------------------------------------------
-
-namespace base {
-
-// -----------------------------------------------------------------------------
-// This is just an abstract base class for waking the two types of waiters
-// -----------------------------------------------------------------------------
-WaitableEvent::WaitableEvent(bool manual_reset, bool initially_signaled)
-    : kernel_(new WaitableEventKernel(manual_reset, initially_signaled)) {
-}
-
-WaitableEvent::~WaitableEvent() {
-}
-
-void WaitableEvent::Reset() {
-  base::AutoLock locked(kernel_->lock_);
-  kernel_->signaled_ = false;
-}
-
-void WaitableEvent::Signal() {
-  base::AutoLock locked(kernel_->lock_);
-
-  if (kernel_->signaled_)
-    return;
-
-  if (kernel_->manual_reset_) {
-    SignalAll();
-    kernel_->signaled_ = true;
-  } else {
-    // In the case of auto reset, if no waiters were woken, we remain
-    // signaled.
-    if (!SignalOne())
-      kernel_->signaled_ = true;
-  }
-}
-
-bool WaitableEvent::IsSignaled() {
-  base::AutoLock locked(kernel_->lock_);
-
-  const bool result = kernel_->signaled_;
-  if (result && !kernel_->manual_reset_)
-    kernel_->signaled_ = false;
-  return result;
-}
-
-// -----------------------------------------------------------------------------
-// Synchronous waits
-
-// -----------------------------------------------------------------------------
-// This is a synchronous waiter. The thread is waiting on the given condition
-// variable and the fired flag in this object.
-// -----------------------------------------------------------------------------
-class SyncWaiter : public WaitableEvent::Waiter {
- public:
-  SyncWaiter()
-      : fired_(false),
-        signaling_event_(NULL),
-        lock_(),
-        cv_(&lock_) {
-  }
-
-  bool Fire(WaitableEvent* signaling_event) {
-    base::AutoLock locked(lock_);
-
-    if (fired_)
-      return false;
-
-    fired_ = true;
-    signaling_event_ = signaling_event;
-
-    cv_.Broadcast();
-
-    // Unlike AsyncWaiter objects, SyncWaiter objects are stack-allocated on
-    // the blocking thread's stack.  There is no |delete this;| in Fire.  The
-    // SyncWaiter object is destroyed when it goes out of scope.
-
-    return true;
-  }
-
-  WaitableEvent* signaling_event() const {
-    return signaling_event_;
-  }
-
-  // ---------------------------------------------------------------------------
-  // These waiters are always stack allocated and don't delete themselves. Thus
-  // there's no problem and the ABA tag is the same as the object pointer.
-  // ---------------------------------------------------------------------------
-  bool Compare(void* tag) {
-    return this == tag;
-  }
-
-  // ---------------------------------------------------------------------------
-  // Called with lock held.
-  // ---------------------------------------------------------------------------
-  bool fired() const {
-    return fired_;
-  }
-
-  // ---------------------------------------------------------------------------
-  // During a TimedWait, we need a way to make sure that an auto-reset
-  // WaitableEvent doesn't think that this event has been signaled between
-  // unlocking it and removing it from the wait-list. Called with lock held.
-  // ---------------------------------------------------------------------------
-  void Disable() {
-    fired_ = true;
-  }
-
-  base::Lock* lock() {
-    return &lock_;
-  }
-
-  base::ConditionVariable* cv() {
-    return &cv_;
-  }
-
- private:
-  bool fired_;
-  WaitableEvent* signaling_event_;  // The WaitableEvent which woke us
-  base::Lock lock_;
-  base::ConditionVariable cv_;
-};
-
-bool WaitableEvent::TimedWait(const TimeDelta& max_time) {
-  const Time end_time(Time::Now() + max_time);
-  const bool finite_time = max_time.ToInternalValue() >= 0;
-
-  kernel_->lock_.Acquire();
-    if (kernel_->signaled_) {
-      if (!kernel_->manual_reset_) {
-        // In this case we were signaled when we had no waiters. Now that
-        // someone has waited upon us, we can automatically reset.
-        kernel_->signaled_ = false;
-      }
-
-      kernel_->lock_.Release();
-      return true;
-    }
-
-    SyncWaiter sw;
-    sw.lock()->Acquire();
-
-    Enqueue(&sw);
-  kernel_->lock_.Release();
-  // We are violating locking order here by holding the SyncWaiter lock but not
-  // the WaitableEvent lock. However, this is safe because we don't lock @lock_
-  // again before unlocking it.
-
-  for (;;) {
-    const Time current_time(Time::Now());
-
-    if (sw.fired() || (finite_time && current_time >= end_time)) {
-      const bool return_value = sw.fired();
-
-      // We can't acquire @lock_ before releasing the SyncWaiter lock (because
-      // of locking order), however, in between the two a signal could be fired
-      // and @sw would accept it, however we will still return false, so the
-      // signal would be lost on an auto-reset WaitableEvent. Thus we call
-      // Disable which makes sw::Fire return false.
-      sw.Disable();
-      sw.lock()->Release();
-
-      kernel_->lock_.Acquire();
-        kernel_->Dequeue(&sw, &sw);
-      kernel_->lock_.Release();
-
-      return return_value;
-    }
-
-    if (finite_time) {
-      const TimeDelta max_wait(end_time - current_time);
-      sw.cv()->TimedWait(max_wait);
-    } else {
-      sw.cv()->Wait();
-    }
-  }
-}
-
-bool WaitableEvent::Wait() {
-  return TimedWait(TimeDelta::FromSeconds(-1));
-}
-
-// -----------------------------------------------------------------------------
-
-
-// -----------------------------------------------------------------------------
-// Synchronous waiting on multiple objects.
-
-static bool  // StrictWeakOrdering
-cmp_fst_addr(const std::pair<WaitableEvent*, unsigned> &a,
-             const std::pair<WaitableEvent*, unsigned> &b) {
-  return a.first < b.first;
-}
-
-// static
-size_t WaitableEvent::WaitMany(WaitableEvent** raw_waitables,
-                               size_t count) {
-  DCHECK(count) << "Cannot wait on no events";
-
-  // We need to acquire the locks in a globally consistent order. Thus we sort
-  // the array of waitables by address. We actually sort a pairs so that we can
-  // map back to the original index values later.
-  std::vector<std::pair<WaitableEvent*, size_t> > waitables;
-  waitables.reserve(count);
-  for (size_t i = 0; i < count; ++i)
-    waitables.push_back(std::make_pair(raw_waitables[i], i));
-
-  DCHECK_EQ(count, waitables.size());
-
-  sort(waitables.begin(), waitables.end(), cmp_fst_addr);
-
-  // The set of waitables must be distinct. Since we have just sorted by
-  // address, we can check this cheaply by comparing pairs of consecutive
-  // elements.
-  for (size_t i = 0; i < waitables.size() - 1; ++i) {
-    DCHECK(waitables[i].first != waitables[i+1].first);
-  }
-
-  SyncWaiter sw;
-
-  const size_t r = EnqueueMany(&waitables[0], count, &sw);
-  if (r) {
-    // One of the events is already signaled. The SyncWaiter has not been
-    // enqueued anywhere. EnqueueMany returns the count of remaining waitables
-    // when the signaled one was seen, so the index of the signaled event is
-    // @count - @r.
-    return waitables[count - r].second;
-  }
-
-  // At this point, we hold the locks on all the WaitableEvents and we have
-  // enqueued our waiter in them all.
-  sw.lock()->Acquire();
-    // Release the WaitableEvent locks in the reverse order
-    for (size_t i = 0; i < count; ++i) {
-      waitables[count - (1 + i)].first->kernel_->lock_.Release();
-    }
-
-    for (;;) {
-      if (sw.fired())
-        break;
-
-      sw.cv()->Wait();
-    }
-  sw.lock()->Release();
-
-  // The address of the WaitableEvent which fired is stored in the SyncWaiter.
-  WaitableEvent *const signaled_event = sw.signaling_event();
-  // This will store the index of the raw_waitables which fired.
-  size_t signaled_index = 0;
-
-  // Take the locks of each WaitableEvent in turn (except the signaled one) and
-  // remove our SyncWaiter from the wait-list
-  for (size_t i = 0; i < count; ++i) {
-    if (raw_waitables[i] != signaled_event) {
-      raw_waitables[i]->kernel_->lock_.Acquire();
-        // There's no possible ABA issue with the address of the SyncWaiter here
-        // because it lives on the stack. Thus the tag value is just the pointer
-        // value again.
-        raw_waitables[i]->kernel_->Dequeue(&sw, &sw);
-      raw_waitables[i]->kernel_->lock_.Release();
-    } else {
-      signaled_index = i;
-    }
-  }
-
-  return signaled_index;
-}
-
-// -----------------------------------------------------------------------------
-// If return value == 0:
-//   The locks of the WaitableEvents have been taken in order and the Waiter has
-//   been enqueued in the wait-list of each. None of the WaitableEvents are
-//   currently signaled
-// else:
-//   None of the WaitableEvent locks are held. The Waiter has not been enqueued
-//   in any of them and the return value is the index of the first WaitableEvent
-//   which was signaled, from the end of the array.
-// -----------------------------------------------------------------------------
-// static
-size_t WaitableEvent::EnqueueMany
-    (std::pair<WaitableEvent*, size_t>* waitables,
-     size_t count, Waiter* waiter) {
-  if (!count)
-    return 0;
-
-  waitables[0].first->kernel_->lock_.Acquire();
-    if (waitables[0].first->kernel_->signaled_) {
-      if (!waitables[0].first->kernel_->manual_reset_)
-        waitables[0].first->kernel_->signaled_ = false;
-      waitables[0].first->kernel_->lock_.Release();
-      return count;
-    }
-
-    const size_t r = EnqueueMany(waitables + 1, count - 1, waiter);
-    if (r) {
-      waitables[0].first->kernel_->lock_.Release();
-    } else {
-      waitables[0].first->Enqueue(waiter);
-    }
-
-    return r;
-}
-
-// -----------------------------------------------------------------------------
-
-
-// -----------------------------------------------------------------------------
-// Private functions...
-
-WaitableEvent::WaitableEventKernel::WaitableEventKernel(bool manual_reset,
-                                                        bool initially_signaled)
-    : manual_reset_(manual_reset),
-      signaled_(initially_signaled) {
-}
-
-WaitableEvent::WaitableEventKernel::~WaitableEventKernel() {
-}
-
-// -----------------------------------------------------------------------------
-// Wake all waiting waiters. Called with lock held.
-// -----------------------------------------------------------------------------
-bool WaitableEvent::SignalAll() {
-  bool signaled_at_least_one = false;
-
-  for (std::list<Waiter*>::iterator
-       i = kernel_->waiters_.begin(); i != kernel_->waiters_.end(); ++i) {
-    if ((*i)->Fire(this))
-      signaled_at_least_one = true;
-  }
-
-  kernel_->waiters_.clear();
-  return signaled_at_least_one;
-}
-
-// ---------------------------------------------------------------------------
-// Try to wake a single waiter. Return true if one was woken. Called with lock
-// held.
-// ---------------------------------------------------------------------------
-bool WaitableEvent::SignalOne() {
-  for (;;) {
-    if (kernel_->waiters_.empty())
-      return false;
-
-    const bool r = (*kernel_->waiters_.begin())->Fire(this);
-    kernel_->waiters_.pop_front();
-    if (r)
-      return true;
-  }
-}
-
-// -----------------------------------------------------------------------------
-// Add a waiter to the list of those waiting. Called with lock held.
-// -----------------------------------------------------------------------------
-void WaitableEvent::Enqueue(Waiter* waiter) {
-  kernel_->waiters_.push_back(waiter);
-}
-
-// -----------------------------------------------------------------------------
-// Remove a waiter from the list of those waiting. Return true if the waiter was
-// actually removed. Called with lock held.
-// -----------------------------------------------------------------------------
-bool WaitableEvent::WaitableEventKernel::Dequeue(Waiter* waiter, void* tag) {
-  for (std::list<Waiter*>::iterator
-       i = waiters_.begin(); i != waiters_.end(); ++i) {
-    if (*i == waiter && (*i)->Compare(tag)) {
-      waiters_.erase(i);
-      return true;
-    }
-  }
-
-  return false;
-}
-
-// -----------------------------------------------------------------------------
-
-}  // namespace base