/* * mutex.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 #endif #ifndef NEED_FTIME #include #endif #include "pthread.h" #include "implement.h" static INLINE int ptw32_mutex_check_need_init(pthread_mutex_t *mutex) { int result = 0; /* * The following guarded test is specifically for statically * initialised mutexes (via PTHREAD_MUTEX_INITIALIZER). * * Note that by not providing this synchronisation we risk * introducing race conditions into applications which are * correctly written. * * Approach * -------- * We know that static mutexes will not be PROCESS_SHARED * so we can serialise access to internal state using * Win32 Critical Sections rather than Win32 Mutexes. * * If using a single global lock slows applications down too much, * multiple global locks could be created and hashed on some random * value associated with each mutex, the pointer perhaps. At a guess, * a good value for the optimal number of global locks might be * the number of processors + 1. * */ EnterCriticalSection(&ptw32_mutex_test_init_lock); /* * We got here possibly under race * conditions. Check again inside the critical section * and only initialise if the mutex is valid (not been destroyed). * If a static mutex has been destroyed, the application can * re-initialise it only by calling pthread_mutex_init() * explicitly. */ if (*mutex == PTHREAD_MUTEX_INITIALIZER) { result = pthread_mutex_init(mutex, NULL); } else if (*mutex == NULL) { /* * The mutex has been destroyed while we were waiting to * initialise it, so the operation that caused the * auto-initialisation should fail. */ result = EINVAL; } LeaveCriticalSection(&ptw32_mutex_test_init_lock); return(result); } int pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *attr) { int result = 0; pthread_mutex_t mx; if (mutex == NULL) { return EINVAL; } if (attr != NULL && *attr != NULL && (*attr)->pshared == PTHREAD_PROCESS_SHARED ) { /* * Creating mutex that can be shared between * processes. */ #if _POSIX_THREAD_PROCESS_SHARED /* * Not implemented yet. */ #error ERROR [__FILE__, line __LINE__]: Process shared mutexes are not supported yet. #else return ENOSYS; #endif /* _POSIX_THREAD_PROCESS_SHARED */ } mx = (pthread_mutex_t) calloc(1, sizeof(*mx)); if (mx == NULL) { result = ENOMEM; } else { mx->lock_idx = PTW32_MUTEX_LOCK_IDX_INIT; mx->recursive_count = 0; mx->kind = (attr == NULL || *attr == NULL ? PTHREAD_MUTEX_DEFAULT : (*attr)->kind); mx->ownerThread = NULL; if ( 0 != sem_init( &mx->wait_sema, 0, 0 )) { result = EAGAIN; free(mx); mx = NULL; } else { InitializeCriticalSection( &mx->wait_cs ); } } *mutex = mx; return(result); } int pthread_mutex_destroy(pthread_mutex_t *mutex) { int result = 0; pthread_mutex_t mx; if (mutex == NULL || *mutex == NULL) { return EINVAL; } /* * Check to see if we have something to delete. */ if (*mutex != PTHREAD_MUTEX_INITIALIZER) { mx = *mutex; result = pthread_mutex_trylock(&mx); /* * The mutex type may not be RECURSIVE therefore trylock may return EBUSY if * we already own the mutex. Here we are assuming that it's OK to destroy * a mutex that we own and have locked recursively. Is this correct? * * For FAST mutexes we record the owner as ANONYMOUS for speed. In this * case we assume that the thread calling pthread_mutex_destroy() is the * owner, if the mutex is owned at all. */ if (result == 0 || mx->ownerThread == (pthread_t) PTW32_MUTEX_OWNER_ANONYMOUS || pthread_equal( mx->ownerThread, pthread_self() ) ) { /* * FIXME!!! * The mutex isn't held by another thread but we could still * be too late invalidating the mutex below since another thread * may already have entered mutex_lock and the check for a valid * *mutex != NULL. */ *mutex = NULL; result = pthread_mutex_unlock(&mx); if (result == 0) { (void) sem_destroy( &mx->wait_sema ); DeleteCriticalSection( &mx->wait_cs ); free(mx); } else { /* * Restore the mutex before we return the error. */ *mutex = mx; } } } else { /* * See notes in ptw32_mutex_check_need_init() above also. */ EnterCriticalSection(&ptw32_mutex_test_init_lock); /* * Check again. */ if (*mutex == PTHREAD_MUTEX_INITIALIZER) { /* * This is all we need to do to destroy a statically * initialised mutex that has not yet been used (initialised). * If we get to here, another thread * waiting to initialise this mutex will get an EINVAL. */ *mutex = NULL; } else { /* * The mutex has been initialised while we were waiting * so assume it's in use. */ result = EBUSY; } LeaveCriticalSection(&ptw32_mutex_test_init_lock); } return(result); } int pthread_mutexattr_init (pthread_mutexattr_t * attr) /* * ------------------------------------------------------ * DOCPUBLIC * Initializes a mutex attributes object with default * attributes. * * PARAMETERS * attr * pointer to an instance of pthread_mutexattr_t * * * DESCRIPTION * Initializes a mutex attributes object with default * attributes. * * NOTES: * 1) Used to define mutex types * * RESULTS * 0 successfully initialized attr, * ENOMEM insufficient memory for attr. * * ------------------------------------------------------ */ { int result = 0; pthread_mutexattr_t ma; ma = (pthread_mutexattr_t) calloc (1, sizeof (*ma)); if (ma == NULL) { result = ENOMEM; } else { ma->pshared = PTHREAD_PROCESS_PRIVATE; ma->kind = PTHREAD_MUTEX_DEFAULT; } *attr = ma; return(result); } /* pthread_mutexattr_init */ int pthread_mutexattr_destroy (pthread_mutexattr_t * attr) /* * ------------------------------------------------------ * DOCPUBLIC * Destroys a mutex attributes object. The object can * no longer be used. * * PARAMETERS * attr * pointer to an instance of pthread_mutexattr_t * * * DESCRIPTION * Destroys a mutex attributes object. The object can * no longer be used. * * NOTES: * 1) Does not affect mutexes created using 'attr' * * RESULTS * 0 successfully released attr, * EINVAL 'attr' is invalid. * * ------------------------------------------------------ */ { int result = 0; if (attr == NULL || *attr == NULL) { result = EINVAL; } else { pthread_mutexattr_t ma = *attr; *attr = NULL; free (ma); } return(result); } /* pthread_mutexattr_destroy */ int pthread_mutexattr_getpshared (const pthread_mutexattr_t * attr, int *pshared) /* * ------------------------------------------------------ * DOCPUBLIC * Determine whether mutexes created with 'attr' can be * shared between processes. * * PARAMETERS * attr * pointer to an instance of pthread_mutexattr_t * * pshared * will be set to one of: * * PTHREAD_PROCESS_SHARED * May be shared if in shared memory * * PTHREAD_PROCESS_PRIVATE * Cannot be shared. * * * DESCRIPTION * Mutexes creatd with 'attr' can be shared between * processes if pthread_mutex_t variable is allocated * in memory shared by these processes. * NOTES: * 1) pshared mutexes MUST be allocated in shared * memory. * 2) The following macro is defined if shared mutexes * are supported: * _POSIX_THREAD_PROCESS_SHARED * * RESULTS * 0 successfully retrieved attribute, * EINVAL 'attr' is invalid, * * ------------------------------------------------------ */ { int result; if ((attr != NULL && *attr != NULL) && (pshared != NULL)) { *pshared = (*attr)->pshared; result = 0; } else { result = EINVAL; } return (result); } /* pthread_mutexattr_getpshared */ int pthread_mutexattr_setpshared (pthread_mutexattr_t * attr, int pshared) /* * ------------------------------------------------------ * DOCPUBLIC * Mutexes created with 'attr' can be shared between * processes if pthread_mutex_t variable is allocated * in memory shared by these processes. * * PARAMETERS * attr * pointer to an instance of pthread_mutexattr_t * * pshared * must be one of: * * PTHREAD_PROCESS_SHARED * May be shared if in shared memory * * PTHREAD_PROCESS_PRIVATE * Cannot be shared. * * DESCRIPTION * Mutexes creatd with 'attr' can be shared between * processes if pthread_mutex_t variable is allocated * in memory shared by these processes. * * NOTES: * 1) pshared mutexes MUST be allocated in shared * memory. * * 2) The following macro is defined if shared mutexes * are supported: * _POSIX_THREAD_PROCESS_SHARED * * RESULTS * 0 successfully set attribute, * EINVAL 'attr' or pshared is invalid, * ENOSYS PTHREAD_PROCESS_SHARED not supported, * * ------------------------------------------------------ */ { int result; if ((attr != NULL && *attr != NULL) && ((pshared == PTHREAD_PROCESS_SHARED) || (pshared == PTHREAD_PROCESS_PRIVATE))) { if (pshared == PTHREAD_PROCESS_SHARED) { #if !defined( _POSIX_THREAD_PROCESS_SHARED ) result = ENOSYS; pshared = PTHREAD_PROCESS_PRIVATE; #else result = 0; #endif /* _POSIX_THREAD_PROCESS_SHARED */ } else { result = 0; } (*attr)->pshared = pshared; } else { result = EINVAL; } return (result); } /* pthread_mutexattr_setpshared */ int pthread_mutexattr_settype (pthread_mutexattr_t * attr, int kind) /* * ------------------------------------------------------ * * DOCPUBLIC * The pthread_mutexattr_settype() and * pthread_mutexattr_gettype() functions respectively set and * get the mutex type attribute. This attribute is set in the * type parameter to these functions. * * PARAMETERS * attr * pointer to an instance of pthread_mutexattr_t * * type * must be one of: * * PTHREAD_MUTEX_DEFAULT * * PTHREAD_MUTEX_NORMAL * * PTHREAD_MUTEX_ERRORCHECK * * PTHREAD_MUTEX_RECURSIVE * * DESCRIPTION * The pthread_mutexattr_settype() and * pthread_mutexattr_gettype() functions respectively set and * get the mutex type attribute. This attribute is set in the * type parameter to these functions. The default value of the * type attribute is PTHREAD_MUTEX_DEFAULT. * * The type of mutex is contained in the type attribute of the * mutex attributes. Valid mutex types include: * * PTHREAD_MUTEX_NORMAL * This type of mutex does not detect deadlock. A * thread attempting to relock this mutex without * first unlocking it will deadlock. Attempting to * unlock a mutex locked by a different thread * results in undefined behavior. Attempting to * unlock an unlocked mutex results in undefined * behavior. * * PTHREAD_MUTEX_ERRORCHECK * This type of mutex provides error checking. A * thread attempting to relock this mutex without * first unlocking it will return with an error. A * thread attempting to unlock a mutex which another * thread has locked will return with an error. A * thread attempting to unlock an unlocked mutex will * return with an error. * * PTHREAD_MUTEX_DEFAULT * Same as PTHREAD_MUTEX_NORMAL. * * PTHREAD_MUTEX_RECURSIVE * A thread attempting to relock this mutex without * first unlocking it will succeed in locking the * mutex. The relocking deadlock which can occur with * mutexes of type PTHREAD_MUTEX_NORMAL cannot occur * with this type of mutex. Multiple locks of this * mutex require the same number of unlocks to * release the mutex before another thread can * acquire the mutex. A thread attempting to unlock a * mutex which another thread has locked will return * with an error. A thread attempting to unlock an * unlocked mutex will return with an error. This * type of mutex is only supported for mutexes whose * process shared attribute is * PTHREAD_PROCESS_PRIVATE. * * RESULTS * 0 successfully set attribute, * EINVAL 'attr' or 'type' is invalid, * * ------------------------------------------------------ */ { int result = 0; if ((attr != NULL && *attr != NULL)) { switch (kind) { case PTHREAD_MUTEX_FAST_NP: case PTHREAD_MUTEX_RECURSIVE_NP: case PTHREAD_MUTEX_ERRORCHECK_NP: (*attr)->kind = kind; break; default: result = EINVAL; break; } } else { result = EINVAL; } return (result); } /* pthread_mutexattr_settype */ int pthread_mutexattr_gettype (pthread_mutexattr_t * attr, int *kind) { int result = 0; if (attr != NULL && *attr != NULL && kind != NULL) { *kind = (*attr)->kind; } else { result = EINVAL; } return (result); } 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. * * 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 */ 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_lock(pthread_mutex_t *mutex) { int result = 0; pthread_mutex_t mx; 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 ((result = sem_wait( &mx->wait_sema )) == 0) { mx->recursive_count = 1; mx->ownerThread = (mx->kind != PTHREAD_MUTEX_FAST_NP ? pthread_self() : (pthread_t) PTW32_MUTEX_OWNER_ANONYMOUS); } } } return(result); } 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. */ { 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 == sem_trywait( &mx->wait_sema ) ) { (void) InterlockedDecrement( &mx->lock_idx ); result = ETIMEDOUT; } LeaveCriticalSection(&mx->wait_cs); 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); } int pthread_mutex_unlock(pthread_mutex_t *mutex) { int result = 0; pthread_mutex_t mx; if (mutex == NULL || *mutex == NULL) { return EINVAL; } mx = *mutex; /* * If the thread calling us holds the mutex then there is no * race condition. If another thread holds the * lock then we shouldn't be in here. */ if (mx != PTHREAD_MUTEX_INITIALIZER) { if (mx->ownerThread == (pthread_t) PTW32_MUTEX_OWNER_ANONYMOUS || pthread_equal(mx->ownerThread, pthread_self())) { if( mx->kind != PTHREAD_MUTEX_RECURSIVE_NP || 0 == --mx->recursive_count ) { mx->ownerThread = NULL; EnterCriticalSection( &mx->wait_cs ); if( InterlockedDecrement( &mx->lock_idx ) >= 0 ) { /* Someone is waiting on that mutex */ if (sem_post( &mx->wait_sema ) != 0) { result = errno; } } LeaveCriticalSection( &mx->wait_cs ); } } else { result = EPERM; } } else { result = EINVAL; } return(result); } int pthread_mutex_trylock(pthread_mutex_t *mutex) { int result = 0; pthread_mutex_t mx; 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) { result = ptw32_mutex_check_need_init(mutex); } mx = *mutex; if (result == 0) { if ( (PTW32_INTERLOCKED_LONG) PTW32_MUTEX_LOCK_IDX_INIT == ptw32_interlocked_compare_exchange((PTW32_INTERLOCKED_LPLONG) &mx->lock_idx, (PTW32_INTERLOCKED_LONG) 0, (PTW32_INTERLOCKED_LONG) PTW32_MUTEX_LOCK_IDX_INIT)) { 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() ) ) { if( mx->kind == PTHREAD_MUTEX_RECURSIVE_NP ) { mx->recursive_count++; } else { result = EDEADLK; } } else { result = EBUSY; } } } return(result); }