| /* |
| * 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 |
