ecency-mobile/ios/Pods/Folly/folly/SpinLock.h

68 lines
1.9 KiB
C++

/*
* Copyright 2016 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* N.B. You most likely do _not_ want to use SpinLock or any other
* kind of spinlock. Use std::mutex instead.
*
* In short, spinlocks in preemptive multi-tasking operating systems
* have serious problems and fast mutexes like std::mutex are almost
* certainly the better choice, because letting the OS scheduler put a
* thread to sleep is better for system responsiveness and throughput
* than wasting a timeslice repeatedly querying a lock held by a
* thread that's blocked, and you can't prevent userspace
* programs blocking.
*
* Spinlocks in an operating system kernel make much more sense than
* they do in userspace.
*/
#pragma once
#include <type_traits>
#include <folly/detail/SpinLockImpl.h>
namespace folly {
#if __x86_64__
typedef SpinLockMslImpl SpinLock;
#elif __APPLE__
typedef SpinLockAppleImpl SpinLock;
#elif FOLLY_HAVE_PTHREAD_SPINLOCK_T
typedef SpinLockPthreadImpl SpinLock;
#else
typedef SpinLockPthreadMutexImpl SpinLock;
#endif
template <typename LOCK>
class SpinLockGuardImpl : private boost::noncopyable {
public:
FOLLY_ALWAYS_INLINE explicit SpinLockGuardImpl(LOCK& lock) :
lock_(lock) {
lock_.lock();
}
FOLLY_ALWAYS_INLINE ~SpinLockGuardImpl() {
lock_.unlock();
}
private:
LOCK& lock_;
};
typedef SpinLockGuardImpl<SpinLock> SpinLockGuard;
}