diff options
| -rw-r--r-- | ChangeLog | 27 | ||||
| -rw-r--r-- | implement.h | 25 | ||||
| -rw-r--r-- | mutex.c | 456 |
3 files changed, 327 insertions, 181 deletions
@@ -1,3 +1,30 @@ +2001-02-12 Ross Johnson <rpj@setup1.ise.canberra.edu.au>
+
+ * mutex.c (pthread_mutex_init): Revamped yet again.
+ (pthread_mutex_destroy): Likewise.
+ (pthread_mutex_lock): Likewise.
+ (pthread_mutex_unlock): Likewise.
+ (pthread_mutex_trylock): Likewise.
+ We now guarantee exclusive access to the pthread_mutex_t
+ (ie. the pointer to the pthread_mutex_t_ struct) and
+ therefore also to the mutex object whether initialised
+ or not. We also ensure that mutex objects are not
+ corrupted by a thread when it is asynchronously
+ canceled (by temporarily setting the thread to DEFERRED
+ cancelation mode). This is to say that the mutex routines
+ now manipulate pthread_mutex_t objects atomically and
+ are cancelation-safe.
+ (ptw32_mutex_check_need_init): Removed - no longer needed.
+ * implement.h (PTW32_OBJECT_GET): New macro to
+ wait and exclusively acquire a pthread_mutex_t object.
+ (PTW32_OBJECT_SET): New macro to set and release a
+ pthread_mutex_t object.
+ (PTW32_OBJECT_TRYGET): New macro to check if another
+ thread is accessing a pthread_mutex_t object and either
+ gives exclusive access or returns immediately.
+ (PTW32_OBJECT_IN_USE): New constant for exclusive access to
+ pthread_mutex_t objects.
+
2001-02-09 Ross Johnson <rpj@setup1.ise.canberra.edu.au>
* nonportable.c (pthread_mutex_setdefaulttype_np): New
diff --git a/implement.h b/implement.h index 8297a46..bd74d55 100644 --- a/implement.h +++ b/implement.h @@ -118,6 +118,31 @@ struct pthread_attr_t_ { * ==================== */ +/* + * The following macros provide exclusive access to an object's pointer. + * See mutex.c:pthread_mutex_lock() for an example. + */ + +#define PTW32_OBJECT_GET(type, ppObject, pDest) \ + while (((pDest) = (type) InterlockedCompareExchangePointer((PVOID *)(ppObject), \ + (PVOID)PTW32_OBJECT_IN_USE, \ + (PVOID)PTW32_OBJECT_IN_USE)) \ + == (type)PTW32_OBJECT_IN_USE) \ + { \ + Sleep(0); \ + } + +#define PTW32_OBJECT_SET(ppObject, value) \ + (void) InterlockedExchangePointer((PVOID *)(ppObject), (PVOID)(value)) + +#define PTW32_OBJECT_TRYGET(type, ppObject, pDest) \ + ((((pDest) = (type) InterlockedExchangePointer((PVOID *)(ppObject), \ + (PVOID)PTW32_OBJECT_IN_USE)) \ + == (type)PTW32_OBJECT_IN_USE) ? ((void) InterlockedExchangePointer((PVOID *)(ppObject), \ + (PVOID)(pDest)) , 0) \ + : 1) + +#define PTW32_OBJECT_IN_USE ((void *) -2) #define PTW32_OBJECT_AUTO_INIT ((void *) -1) #define PTW32_OBJECT_INVALID NULL @@ -29,62 +29,6 @@ #include "pthread.h" #include "implement.h" -static 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_t) PTW32_OBJECT_AUTO_INIT) - { - 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) /* @@ -116,17 +60,47 @@ pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *attr) { int result = 0; pthread_mutex_t mx; + int oldCancelType; if (mutex == NULL) { return EINVAL; } + /* + * We need to prevent us from being canceled + * unexpectedly leaving the mutex in a corrupted state. + * We can do this by temporarily + * setting the thread to DEFERRED cancel type + * and resetting to the original value whenever + * we sleep and when we return. We also check if we've + * been canceled at the same time. + */ + (void) pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, &oldCancelType); + + /* + * This waits until no other thread is looking at the + * (possibly uninitialised) mutex object, then gives + * us exclusive access. + */ + PTW32_OBJECT_GET(pthread_mutex_t, mutex, mx); + + if (mx == NULL) + { + result = EINVAL; + goto FAIL0; + } + + /* + * We now have exclusive access to the mutex pointer + * and structure, whether initialised or not. + */ + mx = (pthread_mutex_t) calloc(1, sizeof(*mx)); if (mx == NULL) { result = ENOMEM; - goto FAIL0; + goto FAIL1; } mx->lock_idx = -1; @@ -180,8 +154,15 @@ pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *attr) mx = NULL; } -FAIL0: - *mutex = mx; + FAIL1: + PTW32_OBJECT_SET(mutex, mx); + + FAIL0: + (void) pthread_mutex_setcanceltype(oldCancelType, NULL); + if (oldCancelType == PTHREAD_CANCEL_ASYNCHRONOUS) + { + pthread_testcancel(); + } return(result); } @@ -212,93 +193,79 @@ pthread_mutex_destroy(pthread_mutex_t *mutex) { int result = 0; pthread_mutex_t mx; + int oldCancelType; - if (mutex == NULL || *mutex == NULL) + if (mutex == NULL) { return EINVAL; } /* - * Check to see if we have something to delete. + * We need to prevent us from being canceled + * unexpectedly leaving the mutex in a corrupted state. + * We can do this by temporarily + * setting the thread to DEFERRED cancel type + * and resetting to the original value whenever + * we sleep and when we return. We also check if we've + * been canceled at the same time. + */ + (void) pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, &oldCancelType); + + /* + * This waits until no other thread is looking at the + * (possibly uninitialised) mutex object, then gives + * us exclusive access. */ - if (*mutex != (pthread_mutex_t) PTW32_OBJECT_AUTO_INIT) + PTW32_OBJECT_GET(pthread_mutex_t, mutex, mx); + + if (mx == NULL) { - mx = *mutex; + result = EINVAL; + goto FAIL0; + } + /* + * We now have exclusive access to the mutex pointer + * and structure, whether initialised or not. + */ + + /* + * Check to see if we have something to delete. + */ + if (mx != (pthread_mutex_t) PTW32_OBJECT_AUTO_INIT) + { /* * Check to see if the mutex is held by any thread. We * can't destroy it if it is. Pthread_mutex_trylock is * not recursive and will return EBUSY even if the current * thread holds the lock. */ - result = pthread_mutex_trylock(&mx); - - if (result == 0) + if (mx->owner != NULL) { - /* - * FIXME!!! - * The mutex isn't held by another thread but we could still - * be too late invalidating the mutex below. Yet we can't do it - * earlier in case another thread needs to unlock the mutex - * that it's holding. - */ - *mutex = NULL; - - result = pthread_mutex_unlock(&mx); - - if (result == 0) - { - free(mx); - } - else - { - /* - * Restore the mutex before we return the error. - */ - *mutex = mx; - } + result = EBUSY; + } + else + { + free(mx); + mx = NULL; } } else { /* - * See notes in ptw32_mutex_check_need_init() above also. + * This is all we need to do to destroy an + * uninitialised statically declared mutex. */ - EnterCriticalSection(&ptw32_mutex_test_init_lock); + mx = NULL; + } - /* - * Check again. - */ - if (*mutex == (pthread_mutex_t) PTW32_OBJECT_AUTO_INIT) - { - /* - * 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 - { - if (*mutex == NULL) - { - /* - * The mutex has been destroyed while we were waiting - * so we just ignore it. - */ - } - else - { - /* - * The mutex has been initialised while we were waiting - * so assume it's in use. - */ - result = EBUSY; - } - } + PTW32_OBJECT_SET(mutex, mx); - LeaveCriticalSection(&ptw32_mutex_test_init_lock); + FAIL0: + (void) pthread_mutex_setcanceltype(oldCancelType, NULL); + if (oldCancelType == PTHREAD_CANCEL_ASYNCHRONOUS) + { + pthread_testcancel(); } return result; @@ -705,43 +672,66 @@ pthread_mutex_lock(pthread_mutex_t *mutex) { int result = 0; pthread_mutex_t mx; + int oldCancelType; - if (mutex == NULL || *mutex == NULL) + if (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. + * We need to prevent us from being canceled + * unexpectedly leaving the mutex in a corrupted state. + * We can do this by temporarily + * setting the thread to DEFERRED cancel type + * and resetting to the original value whenever + * we sleep and when we return. If we are set to + * asynch cancelation then we also check if we've + * been canceled at the same time. + */ + (void) pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, &oldCancelType); + + /* + * This waits until no other thread is looking at the + * (possibly uninitialised) mutex object, then gives + * us exclusive access. */ - if (*mutex == (pthread_mutex_t) PTW32_OBJECT_AUTO_INIT) + PTW32_OBJECT_GET(pthread_mutex_t, mutex, mx); + + if (mx == NULL) { - result = ptw32_mutex_check_need_init(mutex); + result = EINVAL; + goto FAIL0; + } + + /* + * We now have exclusive access to the mutex pointer + * and structure, whether initialised or not. + */ + + if (mx == (pthread_mutex_t) PTW32_OBJECT_AUTO_INIT) + { + result = pthread_mutex_init(&mx); } if (result == 0) { pthread_t self = pthread_self(); - mx = *mutex; - switch (mx->type) { case PTHREAD_MUTEX_DEFAULT: case PTHREAD_MUTEX_RECURSIVE: while (TRUE) { - if (0 == InterlockedIncrement(&mx->lock_idx)) + if (0 == ++mx->lock_idx) { /* - * Ensure that we give other waiting threads a + * The lock is temporarily ours, but + * ensure that we give other waiting threads a * chance to take the mutex if we held it last time. */ - if (InterlockedIncrement(&mx->waiters) > 0 - && mx->lastOwner == self) + if (mx->waiters > 0 && mx->lastOwner == self) { /* * Check to see if other waiting threads @@ -752,7 +742,7 @@ pthread_mutex_lock(pthread_mutex_t *mutex) */ if (mx->lastWaiter == self) { - (void) InterlockedExchange(&mx->waiters, 0L); + mx->waiters = 0; } else { @@ -780,19 +770,27 @@ LOCK_RECURSIVE: goto LOCK_RECURSIVE; } WAIT_RECURSIVE: - InterlockedIncrement(&mx->waiters); + mx->waiters++; mx->lastWaiter = self; - InterlockedDecrement(&mx->lock_idx); + mx->lock_idx--; + PTW32_OBJECT_SET(mutex, mx); + (void) pthread_setcanceltype(oldCancelType, NULL); + if (oldCancelType == PTHREAD_CANCEL_ASYNCHRONOUS) + { + pthread_testcancel(); + } Sleep(0); + (void) pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, NULL); + PTW32_OBJECT_GET(pthread_mutex_t, mutex, mx); /* * Thread priorities may have tricked another * thread into thinking we weren't waiting anymore. - * If so, waiters will equal 0 so set it to 1 - * before we decrement it. + * If so, waiters will equal 0 so just don't + * decrement it. */ - if (InterlockedDecrement(&mx->waiters) < 0) + if (mx->waiters > 0) { - InterlockedExchange(&mx->waiters, 0); + mx->waiters--; } } } @@ -804,24 +802,25 @@ WAIT_RECURSIVE: */ while (TRUE) { - if (0 == InterlockedIncrement(&mx->lock_idx)) + if (0 == ++mx->lock_idx) { /* - * Ensure that we give other waiting threads a + * The lock is temporarily ours, but + * ensure that we give other waiting threads a * chance to take the mutex if we held it last time. */ - if (InterlockedIncrement(&mx->waiters) > 0 - && mx->lastOwner == self) + if (mx->waiters > 0 && mx->lastOwner == self) { /* * Check to see if other waiting threads * have stopped waiting but haven't decremented * the 'waiters' counter - ie. they may have been - * canceled. + * canceled. If we're wrong then waiting threads will + * increment the value again. */ if (mx->lastWaiter == self) { - InterlockedExchange(&mx->waiters, 0L); + mx->waiters = 0L; } else { @@ -843,19 +842,27 @@ WAIT_RECURSIVE: Sleep(0); } WAIT_NORMAL: - InterlockedIncrement(&mx->waiters); + mx->waiters++; mx->lastWaiter = self; - InterlockedDecrement(&mx->lock_idx); + mx->lock_idx--; + PTW32_OBJECT_SET(mutex, mx); + (void) pthread_setcanceltype(oldCancelType, NULL); + if (oldCancelType == PTHREAD_CANCEL_ASYNCHRONOUS) + { + pthread_testcancel(); + } Sleep(0); + (void) pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, NULL); + PTW32_OBJECT_GET(pthread_mutex_t, mutex, mx); /* * Thread priorities may have tricked another * thread into thinking we weren't waiting anymore. - * If so, waiters will equal 0 so set it to 1 - * before we decrement it. + * If so, waiters will equal 0 so just don't + * decrement it. */ - if (InterlockedDecrement(&mx->waiters) < 0) + if (mx->waiters > 0) { - InterlockedExchange(&mx->waiters, 0); + mx->waiters--; } } } @@ -863,24 +870,25 @@ WAIT_NORMAL: case PTHREAD_MUTEX_ERRORCHECK: while (TRUE) { - if (0 == InterlockedIncrement(&mx->lock_idx)) + if (0 == ++mx->lock_idx) { /* - * Ensure that we give other waiting threads a + * The lock is temporarily ours, but + * ensure that we give other waiting threads a * chance to take the mutex if we held it last time. */ - if (InterlockedIncrement(&mx->waiters) > 0 - && mx->lastOwner == self) + if (mx->waiters > 0 && mx->lastOwner == self) { /* * Check to see if other waiting threads * have stopped waiting but haven't decremented * the 'waiters' counter - ie. they may have been - * canceled. + * canceled. If we're wrong then waiting threads will + * increment the value again. */ if (mx->lastWaiter == self) { - InterlockedExchange(&mx->waiters, 0L); + mx->waiters = 0L; } else { @@ -908,19 +916,27 @@ WAIT_NORMAL: break; } WAIT_ERRORCHECK: - InterlockedIncrement(&mx->waiters); + mx->waiters++; mx->lastWaiter = self; - InterlockedDecrement(&mx->lock_idx); + mx->lock_idx--; + PTW32_OBJECT_SET(mutex, mx); + (void) pthread_setcanceltype(oldCancelType, NULL); + if (oldCancelType == PTHREAD_CANCEL_ASYNCHRONOUS) + { + pthread_testcancel(); + } Sleep(0); + (void) pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, NULL); + PTW32_OBJECT_GET(pthread_mutex_t, mutex, mx); /* * Thread priorities may have tricked another * thread into thinking we weren't waiting anymore. - * If so, waiters will equal 0 so set it to 1 - * before we decrement it. + * If so, waiters will equal 0 so just don't + * decrement it. */ - if (InterlockedDecrement(&mx->waiters) < 0) + if (mx->waiters > 0) { - InterlockedExchange(&mx->waiters, 0); + mx->waiters--; } } } @@ -931,6 +947,15 @@ WAIT_ERRORCHECK: } } + PTW32_OBJECT_SET(mutex, mx); + + FAIL0: + (void) pthread_mutex_setcanceltype(oldCancelType, NULL); + if (oldCancelType == PTHREAD_CANCEL_ASYNCHRONOUS) + { + pthread_testcancel(); + } + return result; } @@ -965,19 +990,43 @@ pthread_mutex_unlock(pthread_mutex_t *mutex) { int result = 0; pthread_mutex_t mx; + int oldCancelType; - if (mutex == NULL || *mutex == NULL) + if (mutex == NULL) { return EINVAL; } - mx = *mutex; + /* + * We need to prevent us from being canceled + * unexpectedly leaving the mutex in a corrupted state. + * We can do this by temporarily + * setting the thread to DEFERRED cancel type + * and resetting to the original value whenever + * we sleep and when we return. If we are set to + * asynch cancelation then we also check if we've + * been canceled at the same time. + */ + (void) pthread_mutex_setcanceltype(PTHREAD_CANCEL_DEFERRED, &oldCancelType); + + /* + * This waits until no other thread is looking at the + * (possibly uninitialised) mutex object, then gives + * us exclusive access. + */ + PTW32_OBJECT_GET(pthread_mutex_t, mutex, mx); + + if (mx == NULL) + { + result = EINVAL; + goto FAIL0; + } - /* - * 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. + /* + * We now have exclusive access to the mutex pointer + * and structure, whether initialised or not. */ + if (mx != (pthread_mutex_t) PTW32_OBJECT_AUTO_INIT && mx->owner == pthread_self()) { @@ -996,13 +1045,22 @@ pthread_mutex_unlock(pthread_mutex_t *mutex) break; } - InterlockedDecrement(&mx->lock_idx); + mx->lock_idx--; } else { result = EPERM; } + PTW32_OBJECT_SET(mutex, mx); + + FAIL0: + (void) pthread_setcanceltype(oldCancelType, NULL); + if (oldCancelType == PTHREAD_CANCEL_ASYNCHRONOUS) + { + pthread_testcancel(); + } + return result; } @@ -1041,24 +1099,51 @@ pthread_mutex_trylock(pthread_mutex_t *mutex) int result = 0; pthread_mutex_t mx; pthread_t self; + int oldCancelType; - if (mutex == NULL || *mutex == NULL) + if (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. + * We need to prevent us from being canceled + * unexpectedly leaving the mutex in a corrupted state. + * We can do this by temporarily + * setting the thread to DEFERRED cancel type + * and resetting to the original value whenever + * we sleep and when we return. If we are set to + * asynch cancelation then we also check if we've + * been canceled at the same time. */ - if (*mutex == (pthread_mutex_t) PTW32_OBJECT_AUTO_INIT) + (void) pthread_mutex_setcanceltype(PTHREAD_CANCEL_DEFERRED, &oldCancelType); + + /* + * If no other thread is looking at the + * (possibly uninitialised) mutex object, then gives + * us exclusive access, otherwise returns immediately. + */ + if (!PTW32_OBJECT_TRYGET(pthread_mutex_t, mutex, mx)) { - result = ptw32_mutex_check_need_init(mutex); + result = EBUSY; + goto FAIL0; } - mx = *mutex; + if (mx == NULL) + { + result = EINVAL; + goto FAIL0; + } + + /* + * We now have exclusive access to the mutex pointer + * and structure, whether initialised or not. + */ + + if (mx == (pthread_mutex_t) PTW32_OBJECT_AUTO_INIT) + { + result = pthread_mutex_init(&mx); + } if (result == 0) { @@ -1093,6 +1178,15 @@ pthread_mutex_trylock(pthread_mutex_t *mutex) } } + PTW32_OBJECT_SET(mutex, mx); + + FAIL0: + (void) pthread_setcanceltype(oldCancelType, NULL); + if (oldCancelType == PTHREAD_CANCEL_ASYNCHRONOUS) + { + pthread_testcancel(); + } + return result; } |