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+// Copyright (c) 2005, 2006, Google Inc.
+// Copyright (c) 2010, Patrick Gansterer <paroga@paroga.com>
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+// * 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.
+// * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "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 THE COPYRIGHT
+// OWNER 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.
+
+// ---
+// Author: Sanjay Ghemawat <opensource@google.com>
+
+#ifndef TCMALLOC_INTERNAL_SPINLOCK_H__
+#define TCMALLOC_INTERNAL_SPINLOCK_H__
+
+#if (CPU(X86) || CPU(X86_64) || CPU(PPC)) && (COMPILER(GCC) || COMPILER(MSVC))
+
+#include <time.h> /* For nanosleep() */
+
+#if HAVE(STDINT_H)
+#include <stdint.h>
+#elif HAVE(INTTYPES_H)
+#include <inttypes.h>
+#else
+#include <sys/types.h>
+#endif
+
+#if OS(WINDOWS)
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+#include <windows.h>
+#else
+#include <sched.h> /* For sched_yield() */
+#endif
+
+static void TCMalloc_SlowLock(volatile unsigned int* lockword);
+
+// The following is a struct so that it can be initialized at compile time
+struct TCMalloc_SpinLock {
+
+ inline void Lock() {
+ int r;
+#if COMPILER(GCC)
+#if CPU(X86) || CPU(X86_64)
+ __asm__ __volatile__
+ ("xchgl %0, %1"
+ : "=r"(r), "=m"(lockword_)
+ : "0"(1), "m"(lockword_)
+ : "memory");
+#else
+ volatile unsigned int *lockword_ptr = &lockword_;
+ __asm__ __volatile__
+ ("1: lwarx %0, 0, %1\n\t"
+ "stwcx. %2, 0, %1\n\t"
+ "bne- 1b\n\t"
+ "isync"
+ : "=&r" (r), "=r" (lockword_ptr)
+ : "r" (1), "1" (lockword_ptr)
+ : "memory");
+#endif
+#elif COMPILER(MSVC)
+ __asm {
+ mov eax, this ; store &lockword_ (which is this+0) in eax
+ mov ebx, 1 ; store 1 in ebx
+ xchg [eax], ebx ; exchange lockword_ and 1
+ mov r, ebx ; store old value of lockword_ in r
+ }
+#endif
+ if (r) TCMalloc_SlowLock(&lockword_);
+ }
+
+ inline void Unlock() {
+#if COMPILER(GCC)
+#if CPU(X86) || CPU(X86_64)
+ __asm__ __volatile__
+ ("movl $0, %0"
+ : "=m"(lockword_)
+ : "m" (lockword_)
+ : "memory");
+#else
+ __asm__ __volatile__
+ ("isync\n\t"
+ "eieio\n\t"
+ "stw %1, %0"
+#if OS(DARWIN) || CPU(PPC)
+ : "=o" (lockword_)
+#else
+ : "=m" (lockword_)
+#endif
+ : "r" (0)
+ : "memory");
+#endif
+#elif COMPILER(MSVC)
+ __asm {
+ mov eax, this ; store &lockword_ (which is this+0) in eax
+ mov [eax], 0 ; set lockword_ to 0
+ }
+#endif
+ }
+ // Report if we think the lock can be held by this thread.
+ // When the lock is truly held by the invoking thread
+ // we will always return true.
+ // Indended to be used as CHECK(lock.IsHeld());
+ inline bool IsHeld() const {
+ return lockword_ != 0;
+ }
+
+ inline void Init() { lockword_ = 0; }
+
+ volatile unsigned int lockword_;
+};
+
+#define SPINLOCK_INITIALIZER { 0 }
+
+static void TCMalloc_SlowLock(volatile unsigned int* lockword) {
+// Yield immediately since fast path failed
+#if OS(WINDOWS)
+ Sleep(0);
+#else
+ sched_yield();
+#endif
+ while (true) {
+ int r;
+#if COMPILER(GCC)
+#if CPU(X86) || CPU(X86_64)
+ __asm__ __volatile__
+ ("xchgl %0, %1"
+ : "=r"(r), "=m"(*lockword)
+ : "0"(1), "m"(*lockword)
+ : "memory");
+
+#else
+ int tmp = 1;
+ __asm__ __volatile__
+ ("1: lwarx %0, 0, %1\n\t"
+ "stwcx. %2, 0, %1\n\t"
+ "bne- 1b\n\t"
+ "isync"
+ : "=&r" (r), "=r" (lockword)
+ : "r" (tmp), "1" (lockword)
+ : "memory");
+#endif
+#elif COMPILER(MSVC)
+ __asm {
+ mov eax, lockword ; assign lockword into eax
+ mov ebx, 1 ; assign 1 into ebx
+ xchg [eax], ebx ; exchange *lockword and 1
+ mov r, ebx ; store old value of *lockword in r
+ }
+#endif
+ if (!r) {
+ return;
+ }
+
+ // This code was adapted from the ptmalloc2 implementation of
+ // spinlocks which would sched_yield() upto 50 times before
+ // sleeping once for a few milliseconds. Mike Burrows suggested
+ // just doing one sched_yield() outside the loop and always
+ // sleeping after that. This change helped a great deal on the
+ // performance of spinlocks under high contention. A test program
+ // with 10 threads on a dual Xeon (four virtual processors) went
+ // from taking 30 seconds to 16 seconds.
+
+ // Sleep for a few milliseconds
+#if OS(WINDOWS)
+ Sleep(2);
+#else
+ struct timespec tm;
+ tm.tv_sec = 0;
+ tm.tv_nsec = 2000001;
+ nanosleep(&tm, NULL);
+#endif
+ }
+}
+
+#elif OS(WINDOWS)
+
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+#include <windows.h>
+
+static void TCMalloc_SlowLock(LPLONG lockword);
+
+// The following is a struct so that it can be initialized at compile time
+struct TCMalloc_SpinLock {
+
+ inline void Lock() {
+ if (InterlockedExchange(&m_lockword, 1))
+ TCMalloc_SlowLock(&m_lockword);
+ }
+
+ inline void Unlock() {
+ InterlockedExchange(&m_lockword, 0);
+ }
+
+ inline bool IsHeld() const {
+ return m_lockword != 0;
+ }
+
+ inline void Init() { m_lockword = 0; }
+
+ LONG m_lockword;
+};
+
+#define SPINLOCK_INITIALIZER { 0 }
+
+static void TCMalloc_SlowLock(LPLONG lockword) {
+ Sleep(0); // Yield immediately since fast path failed
+ while (InterlockedExchange(lockword, 1))
+ Sleep(2);
+}
+
+#else
+
+#include <pthread.h>
+
+// Portable version
+struct TCMalloc_SpinLock {
+ pthread_mutex_t private_lock_;
+
+ inline void Init() {
+ if (pthread_mutex_init(&private_lock_, NULL) != 0) CRASH();
+ }
+ inline void Finalize() {
+ if (pthread_mutex_destroy(&private_lock_) != 0) CRASH();
+ }
+ inline void Lock() {
+ if (pthread_mutex_lock(&private_lock_) != 0) CRASH();
+ }
+ inline void Unlock() {
+ if (pthread_mutex_unlock(&private_lock_) != 0) CRASH();
+ }
+ bool IsHeld() {
+ if (pthread_mutex_trylock(&private_lock_))
+ return true;
+
+ Unlock();
+ return false;
+ }
+};
+
+#define SPINLOCK_INITIALIZER { PTHREAD_MUTEX_INITIALIZER }
+
+#endif
+
+// Corresponding locker object that arranges to acquire a spinlock for
+// the duration of a C++ scope.
+class TCMalloc_SpinLockHolder {
+ private:
+ TCMalloc_SpinLock* lock_;
+ public:
+ inline explicit TCMalloc_SpinLockHolder(TCMalloc_SpinLock* l)
+ : lock_(l) { l->Lock(); }
+ inline ~TCMalloc_SpinLockHolder() { lock_->Unlock(); }
+};
+
+// Short-hands for convenient use by tcmalloc.cc
+typedef TCMalloc_SpinLock SpinLock;
+typedef TCMalloc_SpinLockHolder SpinLockHolder;
+
+#endif // TCMALLOC_INTERNAL_SPINLOCK_H__
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