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-rw-r--r--security/sandbox/chromium/base/synchronization/waitable_event_posix.cc417
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diff --git a/security/sandbox/chromium/base/synchronization/waitable_event_posix.cc b/security/sandbox/chromium/base/synchronization/waitable_event_posix.cc
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index 64d4376fe..000000000
--- a/security/sandbox/chromium/base/synchronization/waitable_event_posix.cc
+++ /dev/null
@@ -1,417 +0,0 @@
-// Copyright (c) 2012 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 <stddef.h>
-
-#include <algorithm>
-#include <vector>
-
-#include "base/logging.h"
-#include "base/synchronization/condition_variable.h"
-#include "base/synchronization/lock.h"
-#include "base/synchronization/waitable_event.h"
-#include "base/threading/thread_restrictions.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) override {
- 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) override { 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_;
-};
-
-void WaitableEvent::Wait() {
- bool result = TimedWait(TimeDelta::FromSeconds(-1));
- DCHECK(result) << "TimedWait() should never fail with infinite timeout";
-}
-
-bool WaitableEvent::TimedWait(const TimeDelta& max_time) {
- base::ThreadRestrictions::AssertWaitAllowed();
- const TimeTicks end_time(TimeTicks::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 TimeTicks current_time(TimeTicks::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();
-
- // This is a bug that has been enshrined in the interface of
- // WaitableEvent now: |Dequeue| is called even when |sw.fired()| is true,
- // even though it'll always return false in that case. However, taking
- // the lock ensures that |Signal| has completed before we return and
- // means that a WaitableEvent can synchronise its own destruction.
- 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();
- }
- }
-}
-
-// -----------------------------------------------------------------------------
-// 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) {
- base::ThreadRestrictions::AssertWaitAllowed();
- 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 {
- // By taking this lock here we ensure that |Signal| has completed by the
- // time we return, because |Signal| holds this lock. This matches the
- // behaviour of |Wait| and |TimedWait|.
- raw_waitables[i]->kernel_->lock_.Acquire();
- raw_waitables[i]->kernel_->lock_.Release();
- 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
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