/* * Copyright (C) 2009 Andrzej K. Haczewski <ahaczewski@gmail.com> * * DISCLAIMER: The implementation is Git-specific, it is subset of original * Pthreads API, without lots of other features that Git doesn't use. * Git also makes sure that the passed arguments are valid, so there's * no need for double-checking. */ #include "../../git-compat-util.h" #include "pthread.h" #include <errno.h> #include <limits.h> static unsigned __stdcall win32_start_routine(void *arg) { pthread_t *thread = arg; thread->tid = GetCurrentThreadId(); thread->arg = thread->start_routine(thread->arg); return 0; } int pthread_create(pthread_t *thread, const void *unused, void *(*start_routine)(void*), void *arg) { thread->arg = arg; thread->start_routine = start_routine; thread->handle = (HANDLE) _beginthreadex(NULL, 0, win32_start_routine, thread, 0, NULL); if (!thread->handle) return errno; else return 0; } int win32_pthread_join(pthread_t *thread, void **value_ptr) { DWORD result = WaitForSingleObject(thread->handle, INFINITE); switch (result) { case WAIT_OBJECT_0: if (value_ptr) *value_ptr = thread->arg; return 0; case WAIT_ABANDONED: return EINVAL; default: return err_win_to_posix(GetLastError()); } } pthread_t pthread_self(void) { pthread_t t = { NULL }; t.tid = GetCurrentThreadId(); return t; } int pthread_cond_init(pthread_cond_t *cond, const void *unused) { cond->waiters = 0; cond->was_broadcast = 0; InitializeCriticalSection(&cond->waiters_lock); cond->sema = CreateSemaphore(NULL, 0, LONG_MAX, NULL); if (!cond->sema) die("CreateSemaphore() failed"); cond->continue_broadcast = CreateEvent(NULL, /* security */ FALSE, /* auto-reset */ FALSE, /* not signaled */ NULL); /* name */ if (!cond->continue_broadcast) die("CreateEvent() failed"); return 0; } int pthread_cond_destroy(pthread_cond_t *cond) { CloseHandle(cond->sema); CloseHandle(cond->continue_broadcast); DeleteCriticalSection(&cond->waiters_lock); return 0; } int pthread_cond_wait(pthread_cond_t *cond, CRITICAL_SECTION *mutex) { int last_waiter; EnterCriticalSection(&cond->waiters_lock); cond->waiters++; LeaveCriticalSection(&cond->waiters_lock); /* * Unlock external mutex and wait for signal. * NOTE: we've held mutex locked long enough to increment * waiters count above, so there's no problem with * leaving mutex unlocked before we wait on semaphore. */ LeaveCriticalSection(mutex); /* let's wait - ignore return value */ WaitForSingleObject(cond->sema, INFINITE); /* * Decrease waiters count. If we are the last waiter, then we must * notify the broadcasting thread that it can continue. * But if we continued due to cond_signal, we do not have to do that * because the signaling thread knows that only one waiter continued. */ EnterCriticalSection(&cond->waiters_lock); cond->waiters--; last_waiter = cond->was_broadcast && cond->waiters == 0; LeaveCriticalSection(&cond->waiters_lock); if (last_waiter) { /* * cond_broadcast was issued while mutex was held. This means * that all other waiters have continued, but are contending * for the mutex at the end of this function because the * broadcasting thread did not leave cond_broadcast, yet. * (This is so that it can be sure that each waiter has * consumed exactly one slice of the semaphor.) * The last waiter must tell the broadcasting thread that it * can go on. */ SetEvent(cond->continue_broadcast); /* * Now we go on to contend with all other waiters for * the mutex. Auf in den Kampf! */ } /* lock external mutex again */ EnterCriticalSection(mutex); return 0; } /* * IMPORTANT: This implementation requires that pthread_cond_signal * is called while the mutex is held that is used in the corresponding * pthread_cond_wait calls! */ int pthread_cond_signal(pthread_cond_t *cond) { int have_waiters; EnterCriticalSection(&cond->waiters_lock); have_waiters = cond->waiters > 0; LeaveCriticalSection(&cond->waiters_lock); /* * Signal only when there are waiters */ if (have_waiters) return ReleaseSemaphore(cond->sema, 1, NULL) ? 0 : err_win_to_posix(GetLastError()); else return 0; } /* * DOUBLY IMPORTANT: This implementation requires that pthread_cond_broadcast * is called while the mutex is held that is used in the corresponding * pthread_cond_wait calls! */ int pthread_cond_broadcast(pthread_cond_t *cond) { EnterCriticalSection(&cond->waiters_lock); if ((cond->was_broadcast = cond->waiters > 0)) { /* wake up all waiters */ ReleaseSemaphore(cond->sema, cond->waiters, NULL); LeaveCriticalSection(&cond->waiters_lock); /* * At this point all waiters continue. Each one takes its * slice of the semaphor. Now it's our turn to wait: Since * the external mutex is held, no thread can leave cond_wait, * yet. For this reason, we can be sure that no thread gets * a chance to eat *more* than one slice. OTOH, it means * that the last waiter must send us a wake-up. */ WaitForSingleObject(cond->continue_broadcast, INFINITE); /* * Since the external mutex is held, no thread can enter * cond_wait, and, hence, it is safe to reset this flag * without cond->waiters_lock held. */ cond->was_broadcast = 0; } else { LeaveCriticalSection(&cond->waiters_lock); } return 0; }