80 lines
2.1 KiB
C
80 lines
2.1 KiB
C
|
/*
|
||
|
|
* Copyright 2014-present 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 <boost/noncopyable.hpp>
|
||
|
|
|
||
|
|
#include <folly/Portability.h>
|
||
|
|
#include <folly/synchronization/SmallLocks.h>
|
||
|
|
|
||
|
|
namespace folly {
|
||
|
|
|
||
|
|
class SpinLock {
|
||
|
|
public:
|
||
|
|
FOLLY_ALWAYS_INLINE SpinLock() {
|
||
|
|
lock_.init();
|
||
|
|
}
|
||
|
|
FOLLY_ALWAYS_INLINE void lock() const {
|
||
|
|
lock_.lock();
|
||
|
|
}
|
||
|
|
FOLLY_ALWAYS_INLINE void unlock() const {
|
||
|
|
lock_.unlock();
|
||
|
|
}
|
||
|
|
FOLLY_ALWAYS_INLINE bool try_lock() const {
|
||
|
|
return lock_.try_lock();
|
||
|
|
}
|
||
|
|
|
||
|
|
private:
|
||
|
|
mutable folly::MicroSpinLock lock_;
|
||
|
|
};
|
||
|
|
|
||
|
|
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;
|
||
|
|
|
||
|
|
} // namespace folly
|