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/*
* Copyright (C) 2015-2017 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include <wtf/Lock.h>
#include <wtf/LockAlgorithmInlines.h>
#include <wtf/StackShotProfiler.h>
#if OS(WINDOWS)
#include <windows.h>
#else
#include <unistd.h>
#endif
namespace WTF {
static constexpr bool profileLockContention = false;
void Lock::lockSlow()
{
if (profileLockContention)
STACK_SHOT_PROFILE(4, 2, 5);
// Heap allocations are forbidden on certain threads (e.g. audio rendering thread) for performance reasons so we need to
// explicitly allow the following allocation(s). In some rare cases, the lockSlow() algorithm may cause allocations.
DisableMallocRestrictionsForCurrentThreadScope disableMallocRestrictions;
DefaultLockAlgorithm::lockSlow(m_byte);
}
void Lock::unlockSlow()
{
// Heap allocations are forbidden on certain threads (e.g. audio rendering thread) for performance reasons so we need to
// explicitly allow the following allocation(s). In some rare cases, the unlockSlow() algorithm may cause allocations.
DisableMallocRestrictionsForCurrentThreadScope disableMallocRestrictions;
DefaultLockAlgorithm::unlockSlow(m_byte, DefaultLockAlgorithm::Unfair);
}
void Lock::unlockFairlySlow()
{
// Heap allocations are forbidden on certain threads (e.g. audio rendering thread) for performance reasons so we need to
// explicitly allow the following allocation(s). In some rare cases, the unlockSlow() algorithm may cause allocations.
DisableMallocRestrictionsForCurrentThreadScope disableMallocRestrictions;
DefaultLockAlgorithm::unlockSlow(m_byte, DefaultLockAlgorithm::Fair);
}
void Lock::safepointSlow()
{
DefaultLockAlgorithm::safepointSlow(m_byte);
}
bool Lock::tryLockWithTimeout(Seconds timeout)
{
// This function may be called from a signal handler (e.g. via visit()). Hence,
// it should only use APIs that are safe to call from signal handlers. This is
// why we use unistd.h's sleep() instead of its alternatives.
// We'll be doing sleep(1) between tries below. Hence, sleepPerRetry is 1.
unsigned maxRetries = (timeout < Seconds::infinity()) ? timeout.value() : std::numeric_limits<unsigned>::max();
unsigned tryCount = 0;
while (!tryLock() && tryCount++ <= maxRetries) {
#if OS(WINDOWS)
Sleep(1000);
#else
::sleep(1);
#endif
}
return isHeld();
}
} // namespace WTF
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