/* * pthread_mutex_timedlock.c * * Description: * This translation unit implements mutual exclusion (mutex) primitives. * * -------------------------------------------------------------------------- * * Pthreads-win32 - POSIX Threads Library for Win32 * Copyright(C) 1998 John E. Bossom * Copyright(C) 1999,2002 Pthreads-win32 contributors * * Contact Email: rpj@ise.canberra.edu.au * * The current list of contributors is contained * in the file CONTRIBUTORS included with the source * code distribution. The list can also be seen at the * following World Wide Web location: * http://sources.redhat.com/pthreads-win32/contributors.html * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2 of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library in the file COPYING.LIB; * if not, write to the Free Software Foundation, Inc., * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA */ #ifndef _UWIN # include <process.h> #endif #ifndef NEED_FTIME #include <sys/timeb.h> #endif #include "pthread.h" #include "implement.h" static INLINE int ptw32_timed_semwait (sem_t * sem, const struct timespec * abstime) /* * ------------------------------------------------------ * DESCRIPTION * This function waits on a POSIX semaphore. If the * semaphore value is greater than zero, it decreases * its value by one. If the semaphore value is zero, then * the calling thread (or process) is blocked until it can * successfully decrease the value or until abstime. * If abstime has passed when this routine is called then * it returns a result to indicate this. * * If 'abstime' is a NULL pointer then this function will * block until it can successfully decrease the value or * until interrupted by a signal. * * Unlike sem_timedwait(), this routine is not a cancelation point. * * Unlike sem_timedwait(), this routine is non-cancelable. * * RESULTS * 2 abstime has passed already * 1 abstime timed out while waiting * 0 successfully decreased semaphore, * -1 failed, error in errno. * ERRNO * EINVAL 'sem' is not a valid semaphore, * ENOSYS semaphores are not supported, * EINTR the function was interrupted by a signal, * EDEADLK a deadlock condition was detected. * * ------------------------------------------------------ */ { int result = 0; #ifdef NEED_FTIME struct timespec currSysTime; #else /* NEED_FTIME */ struct _timeb currSysTime; #endif /* NEED_FTIME */ const DWORD NANOSEC_PER_MILLISEC = 1000000; const DWORD MILLISEC_PER_SEC = 1000; DWORD milliseconds; DWORD status; if (sem == NULL) { result = EINVAL; } else { if (abstime == NULL) { milliseconds = INFINITE; } else { /* * Calculate timeout as milliseconds from current system time. */ /* get current system time */ #ifdef NEED_FTIME { FILETIME ft; SYSTEMTIME st; GetSystemTime(&st); SystemTimeToFileTime(&st, &ft); /* * GetSystemTimeAsFileTime(&ft); would be faster, * but it does not exist on WinCE */ ptw32_filetime_to_timespec(&ft, &currSysTime); } /* * subtract current system time from abstime */ milliseconds = (abstime->tv_sec - currSysTime.tv_sec) * MILLISEC_PER_SEC; milliseconds += ((abstime->tv_nsec - currSysTime.tv_nsec) + (NANOSEC_PER_MILLISEC/2)) / NANOSEC_PER_MILLISEC; #else /* NEED_FTIME */ _ftime(&currSysTime); /* * subtract current system time from abstime */ milliseconds = (abstime->tv_sec - currSysTime.time) * MILLISEC_PER_SEC; milliseconds += ((abstime->tv_nsec + (NANOSEC_PER_MILLISEC/2)) / NANOSEC_PER_MILLISEC) - currSysTime.millitm; #endif /* NEED_FTIME */ if (((int) milliseconds) < 0) { return 2; } } #ifdef NEED_SEM status = WaitForSingleObject( (*sem)->event, milliseconds ); #else /* NEED_SEM */ status = WaitForSingleObject( (*sem)->sem, milliseconds ); #endif if (status == WAIT_OBJECT_0) { #ifdef NEED_SEM ptw32_decrease_semaphore(sem); #endif /* NEED_SEM */ return 0; } else if (status == WAIT_TIMEOUT) { return 1; } else { result = EINVAL; } } if (result != 0) { errno = result; return -1; } return 0; } /* ptw32_timed_semwait */ int pthread_mutex_timedlock(pthread_mutex_t *mutex, const struct timespec *abstime) { int result = 0; pthread_mutex_t mx; #ifdef NEED_SEM errno = ENOTSUP; return -1; #endif if (mutex == NULL || *mutex == NULL) { return EINVAL; } /* * We do a quick check to see if we need to do more work * to initialise a static mutex. We check * again inside the guarded section of ptw32_mutex_check_need_init() * to avoid race conditions. */ if (*mutex == PTHREAD_MUTEX_INITIALIZER) { if ((result = ptw32_mutex_check_need_init(mutex)) != 0) { return(result); } } mx = *mutex; if( 0 == InterlockedIncrement( &mx->lock_idx ) ) { mx->recursive_count = 1; mx->ownerThread = (mx->kind != PTHREAD_MUTEX_FAST_NP ? pthread_self() : (pthread_t) PTW32_MUTEX_OWNER_ANONYMOUS); } else { if( mx->kind != PTHREAD_MUTEX_FAST_NP && pthread_equal( mx->ownerThread, pthread_self() ) ) { (void) InterlockedDecrement( &mx->lock_idx ); if( mx->kind == PTHREAD_MUTEX_RECURSIVE_NP ) { mx->recursive_count++; } else { result = EDEADLK; } } else { if (abstime == NULL) { result = EINVAL; } else { switch (ptw32_timed_semwait( &mx->wait_sema, abstime )) { case 0: /* We got the mutex. */ { mx->recursive_count = 1; mx->ownerThread = (mx->kind != PTHREAD_MUTEX_FAST_NP ? pthread_self() : (pthread_t) PTW32_MUTEX_OWNER_ANONYMOUS); break; } case 1: /* Timedout, try a second grab. */ { int busy; EnterCriticalSection(&mx->wait_cs); /* * If we timeout, it is up to us to adjust lock_idx to say * we're no longer waiting. If the mutex was also unlocked * while we were timing out, and we simply return ETIMEDOUT, * then wait_sema would be left in a state that is not consistent * with the state of lock_idx. * * We must check to see if wait_sema has just been posted * but we can't just call sem_getvalue - we must compete for * the semaphore using sem_trywait(), otherwise we would need * additional critical sections elsewhere, which would make the * logic too inefficient. * * If sem_trywait returns EAGAIN then either wait_sema * was given directly to another waiting thread or * another thread has called sem_*wait() before us and * taken the lock. Then we MUST decrement lock_idx and return * ETIMEDOUT. * * Otherwise we MUST return success (because we have effectively * acquired the lock that would have been ours had we not * timed out), and NOT decrement lock_idx. * * We can almost guarrantee that EAGAIN is the only * possible error, so no need to test errno. */ if ( -1 == (busy = sem_trywait( &mx->wait_sema )) ) { (void) InterlockedDecrement( &mx->lock_idx ); result = ETIMEDOUT; } LeaveCriticalSection(&mx->wait_cs); if ( ! busy ) { /* * We have acquired the lock on second grab - keep it. */ mx->recursive_count = 1; mx->ownerThread = (mx->kind != PTHREAD_MUTEX_FAST_NP ? pthread_self() : (pthread_t) PTW32_MUTEX_OWNER_ANONYMOUS); } break; } case 2: /* abstime passed before we started to wait. */ { /* * If we timeout, it is up to us to adjust lock_idx to say * we're no longer waiting. * * The owner thread may still have posted wait_sema thinking * we were waiting. I believe we must check but then NOT do any * programmed work if we have acquired the mutex because * we don't how long ago abstime was. We MUST just release it * immediately. */ EnterCriticalSection(&mx->wait_cs); result = ETIMEDOUT; if ( -1 == sem_trywait( &mx->wait_sema ) ) { (void) InterlockedDecrement( &mx->lock_idx ); } else { if ( InterlockedDecrement( &mx->lock_idx ) >= 0 ) { /* Someone else is waiting on that mutex */ if ( sem_post( &mx->wait_sema ) != 0 ) { result = errno; } } } LeaveCriticalSection(&mx->wait_cs); break; } default: { result = errno; break; } } } } } return(result); }