diff options
Diffstat (limited to 'js/src/threading')
| -rw-r--r-- | js/src/threading/windows/ConditionVariable.cpp | 329 |
1 files changed, 7 insertions, 322 deletions
diff --git a/js/src/threading/windows/ConditionVariable.cpp b/js/src/threading/windows/ConditionVariable.cpp index 868c35141..3c75a0f27 100644 --- a/js/src/threading/windows/ConditionVariable.cpp +++ b/js/src/threading/windows/ConditionVariable.cpp @@ -28,342 +28,34 @@ _InterlockedIncrement((volatile long*)(addend)) #endif -// Windows XP and Server 2003 don't support condition variables natively. The -// NativeImports class is responsible for detecting native support and -// retrieving the appropriate function pointers. It gets instantiated once, -// using a static initializer. -class ConditionVariableNativeImports -{ -public: - ConditionVariableNativeImports() { - HMODULE kernel32_dll = GetModuleHandle("kernel32.dll"); - MOZ_RELEASE_ASSERT(kernel32_dll != NULL); - -#define LOAD_SYMBOL(symbol) loadSymbol(kernel32_dll, #symbol, symbol) - supported_ = LOAD_SYMBOL(InitializeConditionVariable) && - LOAD_SYMBOL(WakeConditionVariable) && - LOAD_SYMBOL(WakeAllConditionVariable) && - LOAD_SYMBOL(SleepConditionVariableCS); -#undef LOAD_SYMBOL - } - - inline bool supported() const { - return supported_; - } - - void(WINAPI* InitializeConditionVariable)(CONDITION_VARIABLE* ConditionVariable); - void(WINAPI* WakeAllConditionVariable)(PCONDITION_VARIABLE ConditionVariable); - void(WINAPI* WakeConditionVariable)(CONDITION_VARIABLE* ConditionVariable); - BOOL(WINAPI* SleepConditionVariableCS)(CONDITION_VARIABLE* ConditionVariable, - CRITICAL_SECTION* CriticalSection, - DWORD dwMilliseconds); - -private: - template <typename T> - inline bool loadSymbol(HMODULE module, const char* name, T& fn) { - FARPROC ptr = GetProcAddress(module, name); - if (!ptr) - return false; - - fn = reinterpret_cast<T>(ptr); - return true; - } - - bool supported_; -}; - -static ConditionVariableNativeImports sNativeImports; - // Wrapper for native condition variable APIs. -struct ConditionVariableNative -{ - inline void initialize() { - sNativeImports.InitializeConditionVariable(&cv_); - } - - inline void destroy() { - // Native condition variables don't require cleanup. - } - - inline void notify_one() { sNativeImports.WakeConditionVariable(&cv_); } - - inline void notify_all() { sNativeImports.WakeAllConditionVariable(&cv_); } - - inline bool wait(CRITICAL_SECTION* cs, DWORD msec) { - return sNativeImports.SleepConditionVariableCS(&cv_, cs, msec); - } - -private: - CONDITION_VARIABLE cv_; -}; - -// Fallback condition variable support for Windows XP and Server 2003. Given the -// difficulty of testing on these antiquated platforms and their rapidly -// diminishing market share, this implementation trades performance for -// predictable behavior. -struct ConditionVariableFallback -{ - static const uint32_t WAKEUP_MODE_NONE = 0; - static const uint32_t WAKEUP_MODE_ONE = 0x40000000; - static const uint32_t WAKEUP_MODE_ALL = 0x80000000; - - static const uint32_t WAKEUP_MODE_MASK = WAKEUP_MODE_ONE | WAKEUP_MODE_ALL; - static const uint32_t SLEEPERS_COUNT_MASK = ~WAKEUP_MODE_MASK; - - void initialize() - { - // Initialize the state variable to 0 sleepers, no wakeup. - sleepersCountAndWakeupMode_ = 0 | WAKEUP_MODE_NONE; - - // Create a semaphore that prevents threads from entering sleep, - // or waking other threads while a wakeup is ongoing. - sleepWakeupSemaphore_ = CreateSemaphoreW(NULL, 1, 1, NULL); - MOZ_RELEASE_ASSERT(sleepWakeupSemaphore_); - - // Use an auto-reset event for waking up a single sleeper. - wakeOneEvent_ = CreateEventW(NULL, FALSE, FALSE, NULL); - MOZ_RELEASE_ASSERT(wakeOneEvent_); - - // Use a manual-reset event for waking up all sleepers. - wakeAllEvent_ = CreateEventW(NULL, TRUE, FALSE, NULL); - MOZ_RELEASE_ASSERT(wakeAllEvent_); - } - - void destroy() - { - BOOL r; - - MOZ_RELEASE_ASSERT(sleepersCountAndWakeupMode_ == (0 | WAKEUP_MODE_NONE)); - - r = CloseHandle(sleepWakeupSemaphore_); - MOZ_RELEASE_ASSERT(r); - - r = CloseHandle(wakeOneEvent_); - MOZ_RELEASE_ASSERT(r); - - r = CloseHandle(wakeAllEvent_); - MOZ_RELEASE_ASSERT(r); - } - -private: - void wakeup(uint32_t wakeupMode, HANDLE wakeEvent) - { - // Ensure that only one thread at a time can wake up others. - BOOL result = WaitForSingleObject(sleepWakeupSemaphore_, INFINITE); - MOZ_RELEASE_ASSERT(result == WAIT_OBJECT_0); - - // Atomically set the wakeup mode and retrieve the number of sleepers. - uint32_t wcwm = InterlockedExchangeAdd(&sleepersCountAndWakeupMode_, - wakeupMode); - uint32_t sleepersCount = wcwm & SLEEPERS_COUNT_MASK; - MOZ_RELEASE_ASSERT((wcwm & WAKEUP_MODE_MASK) == WAKEUP_MODE_NONE); - - if (sleepersCount > 0) { - // If there are any sleepers, set the wake event. The (last) woken - // up thread is responsible for releasing the semaphore. - BOOL success = SetEvent(wakeEvent); - MOZ_RELEASE_ASSERT(success); - - } else { - // If there are no sleepers, set the wakeup mode back to 'none' - // and release the semaphore ourselves. - sleepersCountAndWakeupMode_ = 0 | WAKEUP_MODE_NONE; - - BOOL success = ReleaseSemaphore(sleepWakeupSemaphore_, 1, NULL); - MOZ_RELEASE_ASSERT(success); - } - } - -public: - void notify_one() { wakeup(WAKEUP_MODE_ONE, wakeOneEvent_); } - - void notify_all() { wakeup(WAKEUP_MODE_ALL, wakeAllEvent_); } - - bool wait(CRITICAL_SECTION* userLock, DWORD msec) - { - // Make sure that we can't enter sleep when there are other threads - // that still need to wake up on either of the wake events being set. - DWORD result = WaitForSingleObject(sleepWakeupSemaphore_, INFINITE); - MOZ_RELEASE_ASSERT(result == WAIT_OBJECT_0); - - // Register ourselves as a sleeper. Use an atomic operation, because - // if another thread times out at the same time, it will decrement the - // sleepers count without acquiring the semaphore. - uint32_t wcwm = InterlockedIncrement(&sleepersCountAndWakeupMode_); - MOZ_RELEASE_ASSERT((wcwm & WAKEUP_MODE_MASK) == WAKEUP_MODE_NONE); - - // Now that that this thread has been enlisted as a sleeper, it is safe - // again for other threads to do a wakeup. - BOOL success = ReleaseSemaphore(sleepWakeupSemaphore_, 1, NULL); - MOZ_RELEASE_ASSERT(success); - - // Release the caller's mutex. - LeaveCriticalSection(userLock); - - // Wait for either event to become signaled, which happens when - // notify_one() or notify_all() is called, or for a timeout. - HANDLE handles[2] = { wakeOneEvent_, wakeAllEvent_ }; - DWORD waitResult = WaitForMultipleObjects(2, handles, FALSE, msec); - MOZ_RELEASE_ASSERT(waitResult == WAIT_OBJECT_0 || - waitResult == WAIT_OBJECT_0 + 1 || - (waitResult == WAIT_TIMEOUT && msec != INFINITE)); - - // Atomically decrease the sleepers count and retrieve the wakeup mode - // and new sleepers count. - // If the wait returned because wakeOneEvent_ was set, we are certain - // that the wakeup mode will be WAKEUP_MODE_ONE. In that case, - // atomically reset the wakeup mode to 'none', because if another - // thread's sleep times out at same time and it finds that it was the - // last sleeper, it decides whether or not to reset the wakeOneEvent_ - // based on the current wakeup mode. - uint32_t sub; - if (waitResult == WAIT_OBJECT_0) - sub = 1 | WAKEUP_MODE_ONE; - else - sub = 1; - // Note that InterlockedExchangeAdd returns the old value, but it's - // easier to work with the new value. - wcwm = InterlockedExchangeAdd(&sleepersCountAndWakeupMode_, -sub) - sub; - - uint32_t wakeupMode = wcwm & WAKEUP_MODE_MASK; - uint32_t sleepersCount = wcwm & SLEEPERS_COUNT_MASK; - - bool releaseSleepWakeupSemaphore = false; - - if (waitResult == WAIT_OBJECT_0) { - // The wake-one event is an auto-reset event so if we're woken by - // it, it should already have been reset. We also already removed - // the WAKEUP_MODE_ONE bit so the wakeup mode should now be 'none' - // again. - MOZ_RELEASE_ASSERT(wakeupMode == WAKEUP_MODE_NONE); - - // The signaling thread has acquired the enter-wakeup semaphore and - // expects the woken (this) thread to release it again. - releaseSleepWakeupSemaphore = true; - - } else if (waitResult == WAIT_TIMEOUT && wakeupMode == WAKEUP_MODE_ONE && - sleepersCount == 0) { - // In theory a race condition is possible where the last sleeper - // times out right at the moment that another thread signals it. - // If that just happened we now have a dangling signal event and - // mode, but no threads to be woken up by it, and we need to clean - // that up. - BOOL success = ResetEvent(wakeOneEvent_); - MOZ_RELEASE_ASSERT(success); - - // This is safe - we are certain there are no other sleepers that - // could wake up right now, and the semaphore ensures that no - // non-sleeping threads are messing with - // sleepersCountAndWakeupMode_. - sleepersCountAndWakeupMode_ = 0 | WAKEUP_MODE_NONE; - - // The signaling thread has acquired the sleep-wakeup semaphore and - // expects the woken thread to release it. But since there are no - // sleeping threads left this thread will do it instead. - releaseSleepWakeupSemaphore = true; - - } else if (wakeupMode == WAKEUP_MODE_ALL && sleepersCount == 0) { - // If this was the last thread waking up in response to a - // notify_all, clear the wakeup mode and reset the wake-all event. - // A race condition similar to the case described above could - // occur, so waitResult could be WAIT_TIMEOUT, but that doesn't - // matter for the actions that need to be taken. - MOZ_RELEASE_ASSERT(waitResult = WAIT_OBJECT_0 + 1 || - waitResult == WAIT_TIMEOUT); - - BOOL success = ResetEvent(wakeAllEvent_); - MOZ_RELEASE_ASSERT(success); - - sleepersCountAndWakeupMode_ = 0 | WAKEUP_MODE_NONE; - - // The broadcasting thread has acquired the enter-wakeup semaphore - // and expects the last thread that wakes up to release it. - releaseSleepWakeupSemaphore = true; - - } else if ((waitResult == WAIT_TIMEOUT && msec != INFINITE) || - (waitResult == WAIT_OBJECT_0 + 1 && - wakeupMode == WAKEUP_MODE_ALL)) { - // Either: - // * The wait timed out but found no active notify_one or notify_all - // the moment it decreased the wait count. - // * A notify_all woke up this thread but there are more threads - // that need to be woken up by the wake-all event. - // These are ordinary conditions in which we don't have to do - // anything. - - } else { - MOZ_CRASH("invalid wakeup condition"); - } - - // Release the enter-wakeup semaphore if the wakeup condition requires - // us to do it. - if (releaseSleepWakeupSemaphore) { - BOOL success = ReleaseSemaphore(sleepWakeupSemaphore_, 1, NULL); - MOZ_RELEASE_ASSERT(success); - } - - // Reacquire the user mutex. - EnterCriticalSection(userLock); - - // Return true if woken up, false when timed out. - if (waitResult == WAIT_TIMEOUT) { - SetLastError(ERROR_TIMEOUT); - return false; - } - return true; - } - -private: - uint32_t sleepersCountAndWakeupMode_; - HANDLE sleepWakeupSemaphore_; - HANDLE wakeOneEvent_; - HANDLE wakeAllEvent_; -}; - struct js::ConditionVariable::PlatformData { - union - { - ConditionVariableNative native; - ConditionVariableFallback fallback; - }; + CONDITION_VARIABLE cv_; }; js::ConditionVariable::ConditionVariable() { - if (sNativeImports.supported()) - platformData()->native.initialize(); - else - platformData()->fallback.initialize(); + InitializeConditionVariable(&platformData()->cv_); } void js::ConditionVariable::notify_one() { - if (sNativeImports.supported()) - platformData()->native.notify_one(); - else - platformData()->fallback.notify_one(); + WakeConditionVariable(&platformData()->cv_); } void js::ConditionVariable::notify_all() { - if (sNativeImports.supported()) - platformData()->native.notify_all(); - else - platformData()->fallback.notify_all(); + WakeAllConditionVariable(&platformData()->cv_); } void js::ConditionVariable::wait(UniqueLock<Mutex>& lock) { CRITICAL_SECTION* cs = &lock.lock.platformData()->criticalSection; - bool r; - if (sNativeImports.supported()) - r = platformData()->native.wait(cs, INFINITE); - else - r = platformData()->fallback.wait(cs, INFINITE); + bool r = SleepConditionVariableCS(&platformData()->cv_, cs, INFINITE); MOZ_RELEASE_ASSERT(r); } @@ -390,11 +82,7 @@ js::ConditionVariable::wait_for(UniqueLock<Mutex>& lock, ? INFINITE : static_cast<DWORD>(msecd); - BOOL r; - if (sNativeImports.supported()) - r = platformData()->native.wait(cs, msec); - else - r = platformData()->fallback.wait(cs, msec); + BOOL r = SleepConditionVariableCS(&platformData()->cv_, cs, msec); if (r) return CVStatus::NoTimeout; MOZ_RELEASE_ASSERT(GetLastError() == ERROR_TIMEOUT); @@ -403,10 +91,7 @@ js::ConditionVariable::wait_for(UniqueLock<Mutex>& lock, js::ConditionVariable::~ConditionVariable() { - if (sNativeImports.supported()) - platformData()->native.destroy(); - else - platformData()->fallback.destroy(); + // Native condition variables don't require cleanup. } inline js::ConditionVariable::PlatformData* |