blob: 1e2e1c3c0c084e33c2ea31aaa8551eb0326dd455 [file] [log] [blame]
/*
* Copyright (C) 2014 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 "ScopeExit.h"
#include "StaticMutex.h"
#include <thread>
namespace bmalloc {
void StaticMutex::lockSlowCase()
{
// The longest critical section in bmalloc is much shorter than the
// time it takes to make a system call to yield to the OS scheduler.
// So, we try again a lot before we yield.
static const size_t aLot = 256;
if (!m_isSpinning.test_and_set()) {
auto clear = makeScopeExit([&] { m_isSpinning.clear(); });
for (size_t i = 0; i < aLot; ++i) {
if (try_lock())
return;
}
}
// Avoid spinning pathologically.
while (!try_lock())
sched_yield();
}
} // namespace bmalloc