/*
- * Copyright 2015 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* 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 <folly/detail/SpinLockImpl.h>
+#include <type_traits>
+
+#include <folly/Portability.h>
+#include <folly/SmallLocks.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
+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 {