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Diffstat (limited to 'libutils/include/utils/Mutex.h')
| -rw-r--r-- | libutils/include/utils/Mutex.h | 167 |
1 files changed, 167 insertions, 0 deletions
diff --git a/libutils/include/utils/Mutex.h b/libutils/include/utils/Mutex.h new file mode 100644 index 000000000..d106185f0 --- /dev/null +++ b/libutils/include/utils/Mutex.h @@ -0,0 +1,167 @@ +/* + * Copyright (C) 2007 The Android Open Source Project + * + * 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. + */ + +#ifndef _LIBS_UTILS_MUTEX_H +#define _LIBS_UTILS_MUTEX_H + +#include <stdint.h> +#include <sys/types.h> +#include <time.h> + +#if !defined(_WIN32) +# include <pthread.h> +#endif + +#include <utils/Errors.h> +#include <utils/Timers.h> + +// --------------------------------------------------------------------------- +namespace android { +// --------------------------------------------------------------------------- + +class Condition; + +/* + * NOTE: This class is for code that builds on Win32. Its usage is + * deprecated for code which doesn't build for Win32. New code which + * doesn't build for Win32 should use std::mutex and std::lock_guard instead. + * + * Simple mutex class. The implementation is system-dependent. + * + * The mutex must be unlocked by the thread that locked it. They are not + * recursive, i.e. the same thread can't lock it multiple times. + */ +class Mutex { +public: + enum { + PRIVATE = 0, + SHARED = 1 + }; + + Mutex(); + explicit Mutex(const char* name); + explicit Mutex(int type, const char* name = NULL); + ~Mutex(); + + // lock or unlock the mutex + status_t lock(); + void unlock(); + + // lock if possible; returns 0 on success, error otherwise + status_t tryLock(); + +#if defined(__ANDROID__) + // Lock the mutex, but don't wait longer than timeoutNs (relative time). + // Returns 0 on success, TIMED_OUT for failure due to timeout expiration. + // + // OSX doesn't have pthread_mutex_timedlock() or equivalent. To keep + // capabilities consistent across host OSes, this method is only available + // when building Android binaries. + // + // FIXME?: pthread_mutex_timedlock is based on CLOCK_REALTIME, + // which is subject to NTP adjustments, and includes time during suspend, + // so a timeout may occur even though no processes could run. + // Not holding a partial wakelock may lead to a system suspend. + status_t timedLock(nsecs_t timeoutNs); +#endif + + // Manages the mutex automatically. It'll be locked when Autolock is + // constructed and released when Autolock goes out of scope. + class Autolock { + public: + inline explicit Autolock(Mutex& mutex) : mLock(mutex) { mLock.lock(); } + inline explicit Autolock(Mutex* mutex) : mLock(*mutex) { mLock.lock(); } + inline ~Autolock() { mLock.unlock(); } + private: + Mutex& mLock; + }; + +private: + friend class Condition; + + // A mutex cannot be copied + Mutex(const Mutex&); + Mutex& operator = (const Mutex&); + +#if !defined(_WIN32) + pthread_mutex_t mMutex; +#else + void _init(); + void* mState; +#endif +}; + +// --------------------------------------------------------------------------- + +#if !defined(_WIN32) + +inline Mutex::Mutex() { + pthread_mutex_init(&mMutex, NULL); +} +inline Mutex::Mutex(__attribute__((unused)) const char* name) { + pthread_mutex_init(&mMutex, NULL); +} +inline Mutex::Mutex(int type, __attribute__((unused)) const char* name) { + if (type == SHARED) { + pthread_mutexattr_t attr; + pthread_mutexattr_init(&attr); + pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED); + pthread_mutex_init(&mMutex, &attr); + pthread_mutexattr_destroy(&attr); + } else { + pthread_mutex_init(&mMutex, NULL); + } +} +inline Mutex::~Mutex() { + pthread_mutex_destroy(&mMutex); +} +inline status_t Mutex::lock() { + return -pthread_mutex_lock(&mMutex); +} +inline void Mutex::unlock() { + pthread_mutex_unlock(&mMutex); +} +inline status_t Mutex::tryLock() { + return -pthread_mutex_trylock(&mMutex); +} +#if defined(__ANDROID__) +inline status_t Mutex::timedLock(nsecs_t timeoutNs) { + timeoutNs += systemTime(SYSTEM_TIME_REALTIME); + const struct timespec ts = { + /* .tv_sec = */ static_cast<time_t>(timeoutNs / 1000000000), + /* .tv_nsec = */ static_cast<long>(timeoutNs % 1000000000), + }; + return -pthread_mutex_timedlock(&mMutex, &ts); +} +#endif + +#endif // !defined(_WIN32) + +// --------------------------------------------------------------------------- + +/* + * Automatic mutex. Declare one of these at the top of a function. + * When the function returns, it will go out of scope, and release the + * mutex. + */ + +typedef Mutex::Autolock AutoMutex; + +// --------------------------------------------------------------------------- +}; // namespace android +// --------------------------------------------------------------------------- + +#endif // _LIBS_UTILS_MUTEX_H |