diff options
Diffstat (limited to 'generic/tclThreadJoin.c')
| -rw-r--r-- | generic/tclThreadJoin.c | 311 |
1 files changed, 152 insertions, 159 deletions
diff --git a/generic/tclThreadJoin.c b/generic/tclThreadJoin.c index 3a905b5..f097924 100644 --- a/generic/tclThreadJoin.c +++ b/generic/tclThreadJoin.c @@ -1,66 +1,69 @@ -/* +/* * tclThreadJoin.c -- * - * This file implements a platform independent emulation layer for the - * handling of joinable threads. The Windows platform uses this code to - * provide the functionality of joining threads. This code is currently - * not necessary on Unix. + * This file implements a platform independent emulation layer for + * the handling of joinable threads. The Mac and Windows platforms + * use this code to provide the functionality of joining threads. + * This code is currently not necessary on Unix. * * Copyright (c) 2000 by Scriptics Corporation * - * See the file "license.terms" for information on usage and redistribution of - * this file, and for a DISCLAIMER OF ALL WARRANTIES. + * See the file "license.terms" for information on usage and redistribution + * of this file, and for a DISCLAIMER OF ALL WARRANTIES. */ #include "tclInt.h" -#ifdef WIN32 +#if defined(WIN32) -/* - * The information about each joinable thread is remembered in a structure as - * defined below. +/* The information about each joinable thread is remembered in a + * structure as defined below. */ typedef struct JoinableThread { - Tcl_ThreadId id; /* The id of the joinable thread. */ - int result; /* A place for the result after the demise of - * the thread. */ - int done; /* Boolean flag. Initialized to 0 and set to 1 - * after the exit of the thread. This allows a - * thread requesting a join to detect when - * waiting is not necessary. */ - int waitedUpon; /* Boolean flag. Initialized to 0 and set to 1 - * by the thread waiting for this one via - * Tcl_JoinThread. Used to lock any other - * thread trying to wait on this one. */ - Tcl_Mutex threadMutex; /* The mutex used to serialize access to this - * structure. */ - Tcl_Condition cond; /* This is the condition a thread has to wait - * upon to get notified of the end of the - * described thread. It is signaled indirectly - * by Tcl_ExitThread. */ - struct JoinableThread *nextThreadPtr; - /* Reference to the next thread in the list of - * joinable threads. */ + Tcl_ThreadId id; /* The id of the joinable thread */ + int result; /* A place for the result after the + * demise of the thread */ + int done; /* Boolean flag. Initialized to 0 + * and set to 1 after the exit of + * the thread. This allows a thread + * requesting a join to detect when + * waiting is not necessary. */ + int waitedUpon; /* Boolean flag. Initialized to 0 + * and set to 1 by the thread waiting + * for this one via Tcl_JoinThread. + * Used to lock any other thread + * trying to wait on this one. + */ + Tcl_Mutex threadMutex; /* The mutex used to serialize access + * to this structure. */ + Tcl_Condition cond; /* This is the condition a thread has + * to wait upon to get notified of the + * end of the described thread. It is + * signaled indirectly by + * Tcl_ExitThread. */ + struct JoinableThread* nextThreadPtr; /* Reference to the next thread in the + * list of joinable threads */ } JoinableThread; -/* - * The following variable is used to maintain the global list of all joinable - * threads. Usage by a thread is allowed only if the thread acquired the - * 'joinMutex'. +/* The following variable is used to maintain the global list of all + * joinable threads. Usage by a thread is allowed only if the + * thread acquired the 'joinMutex'. */ TCL_DECLARE_MUTEX(joinMutex) static JoinableThread* firstThreadPtr; + + /* *---------------------------------------------------------------------- * * TclJoinThread -- * - * This procedure waits for the exit of the thread with the specified id - * and returns its result. + * This procedure waits for the exit of the thread with the specified + * id and returns its result. * * Results: * A standard tcl result signaling the overall success/failure of the @@ -69,139 +72,135 @@ static JoinableThread* firstThreadPtr; * * Side effects: * Deallocates the memory allocated by TclRememberJoinableThread. - * Removes the data associated to the thread waited upon from the list of - * joinable threads. + * Removes the data associated to the thread waited upon from the + * list of joinable threads. * *---------------------------------------------------------------------- */ int -TclJoinThread( - Tcl_ThreadId id, /* The id of the thread to wait upon. */ - int *result) /* Reference to a location for the result of - * the thread we are waiting upon. */ +TclJoinThread(id, result) + Tcl_ThreadId id; /* The id of the thread to wait upon. */ + int* result; /* Reference to a location for the result + * of the thread we are waiting upon. */ { - JoinableThread *threadPtr; - - /* - * Steps done here: + /* Steps done here: * i. Acquire the joinMutex and search for the thread. * ii. Error out if it could not be found. * iii. If found, switch from exclusive access to the list to exclusive - * access to the thread structure. + * access to the thread structure. * iv. Error out if some other is already waiting. * v. Skip the waiting part of the thread is already done. * vi. Wait for the thread to exit, mark it as waited upon too. - * vii. Get the result form the structure, + * vii. Get the result form the structure, * viii. switch to exclusive access of the list, * ix. remove the structure from the list, * x. then switch back to exclusive access to the structure * xi. and delete it. */ - Tcl_MutexLock(&joinMutex); + JoinableThread* threadPtr; - threadPtr = firstThreadPtr; - while (threadPtr!=NULL && threadPtr->id!=id) { - threadPtr = threadPtr->nextThreadPtr; - } + Tcl_MutexLock (&joinMutex); + + for (threadPtr = firstThreadPtr; + (threadPtr != (JoinableThread*) NULL) && (threadPtr->id != id); + threadPtr = threadPtr->nextThreadPtr) + /* empty body */ + ; - if (threadPtr == NULL) { - /* - * Thread not found. Either not joinable, or already waited upon and - * exited. Whatever, an error is in order. + if (threadPtr == (JoinableThread*) NULL) { + /* Thread not found. Either not joinable, or already waited + * upon and exited. Whatever, an error is in order. */ - Tcl_MutexUnlock(&joinMutex); - return TCL_ERROR; + Tcl_MutexUnlock (&joinMutex); + return TCL_ERROR; } - /* - * [1] If we don't lock the structure before giving up exclusive access to - * the list some other thread just completing its wait on the same thread - * can delete the structure from under us, leaving us with a dangling - * pointer. + /* [1] If we don't lock the structure before giving up exclusive access + * to the list some other thread just completing its wait on the same + * thread can delete the structure from under us, leaving us with a + * dangling pointer. */ - Tcl_MutexLock(&threadPtr->threadMutex); - Tcl_MutexUnlock(&joinMutex); + Tcl_MutexLock (&threadPtr->threadMutex); + Tcl_MutexUnlock (&joinMutex); - /* - * [2] Now that we have the structure mutex any other thread that just - * tries to delete structure will wait at location [3] until we are done - * with the structure. And in that case we are done with it rather quickly - * as 'waitedUpon' will be set and we will have to error out. + /* [2] Now that we have the structure mutex any other thread that just + * tries to delete structure will wait at location [3] until we are + * done with the structure. And in that case we are done with it + * rather quickly as 'waitedUpon' will be set and we will have to + * error out. */ if (threadPtr->waitedUpon) { - Tcl_MutexUnlock(&threadPtr->threadMutex); + Tcl_MutexUnlock (&threadPtr->threadMutex); return TCL_ERROR; } - /* - * We are waiting now, let other threads recognize this. + /* We are waiting now, let other threads recognize this */ threadPtr->waitedUpon = 1; while (!threadPtr->done) { - Tcl_ConditionWait(&threadPtr->cond, &threadPtr->threadMutex, NULL); + Tcl_ConditionWait (&threadPtr->cond, &threadPtr->threadMutex, NULL); } - /* - * We have to release the structure before trying to access the list again - * or we can run into deadlock with a thread at [1] (see above) because of - * us holding the structure and the other holding the list. There is no - * problem with dangling pointers here as 'waitedUpon == 1' is still valid - * and any other thread will error out and not come to this place. IOW, - * the fact that we are here also means that no other thread came here - * before us and is able to delete the structure. + /* We have to release the structure before trying to access the list + * again or we can run into deadlock with a thread at [1] (see above) + * because of us holding the structure and the other holding the list. + * There is no problem with dangling pointers here as 'waitedUpon == 1' + * is still valid and any other thread will error out and not come to + * this place. IOW, the fact that we are here also means that no other + * thread came here before us and is able to delete the structure. */ - Tcl_MutexUnlock(&threadPtr->threadMutex); - Tcl_MutexLock(&joinMutex); + Tcl_MutexUnlock (&threadPtr->threadMutex); + Tcl_MutexLock (&joinMutex); - /* - * We have to search the list again as its structure may (may, almost + /* We have to search the list again as its structure may (may, almost * certainly) have changed while we were waiting. Especially now is the - * time to compute the predecessor in the list. Any earlier result can be - * dangling by now. + * time to compute the predecessor in the list. Any earlier result can + * be dangling by now. */ if (firstThreadPtr == threadPtr) { - firstThreadPtr = threadPtr->nextThreadPtr; + firstThreadPtr = threadPtr->nextThreadPtr; } else { - JoinableThread *prevThreadPtr = firstThreadPtr; + JoinableThread* prevThreadPtr; + + for (prevThreadPtr = firstThreadPtr; + prevThreadPtr->nextThreadPtr != threadPtr; + prevThreadPtr = prevThreadPtr->nextThreadPtr) + /* empty body */ + ; - while (prevThreadPtr->nextThreadPtr != threadPtr) { - prevThreadPtr = prevThreadPtr->nextThreadPtr; - } prevThreadPtr->nextThreadPtr = threadPtr->nextThreadPtr; } - Tcl_MutexUnlock(&joinMutex); + Tcl_MutexUnlock (&joinMutex); - /* - * [3] Now that the structure is not part of the list anymore no other + /* [3] Now that the structure is not part of the list anymore no other * thread can acquire its mutex from now on. But it is possible that - * another thread is still holding the mutex though, see location [2]. So - * we have to acquire the mutex one more time to wait for that thread to - * finish. We can (and have to) release the mutex immediately. + * another thread is still holding the mutex though, see location [2]. + * So we have to acquire the mutex one more time to wait for that thread + * to finish. We can (and have to) release the mutex immediately. */ - Tcl_MutexLock(&threadPtr->threadMutex); - Tcl_MutexUnlock(&threadPtr->threadMutex); + Tcl_MutexLock (&threadPtr->threadMutex); + Tcl_MutexUnlock (&threadPtr->threadMutex); - /* - * Copy the result to us, finalize the synchronisation objects, then free - * the structure and return. + /* Copy the result to us, finalize the synchronisation objects, then + * free the structure and return. */ *result = threadPtr->result; - Tcl_ConditionFinalize(&threadPtr->cond); - Tcl_MutexFinalize(&threadPtr->threadMutex); - ckfree((char *) threadPtr); + Tcl_ConditionFinalize (&threadPtr->cond); + Tcl_MutexFinalize (&threadPtr->threadMutex); + ckfree ((VOID*) threadPtr); return TCL_OK; } @@ -212,37 +211,39 @@ TclJoinThread( * TclRememberJoinableThread -- * * This procedure remebers a thread as joinable. Only a call to - * TclJoinThread will remove the structre created (and initialized) here. - * IOW, not waiting upon a joinable thread will cause memory leaks. + * TclJoinThread will remove the structre created (and initialized) + * here. IOW, not waiting upon a joinable thread will cause memory + * leaks. * * Results: * None. * * Side effects: - * Allocates memory, adds it to the global list of all joinable threads. + * Allocates memory, adds it to the global list of all joinable + * threads. * *---------------------------------------------------------------------- */ -void -TclRememberJoinableThread( - Tcl_ThreadId id) /* The thread to remember as joinable */ +VOID +TclRememberJoinableThread(id) + Tcl_ThreadId id; /* The thread to remember as joinable */ { - JoinableThread *threadPtr; + JoinableThread* threadPtr; - threadPtr = (JoinableThread *) ckalloc(sizeof(JoinableThread)); - threadPtr->id = id; - threadPtr->done = 0; - threadPtr->waitedUpon = 0; + threadPtr = (JoinableThread*) ckalloc (sizeof (JoinableThread)); + threadPtr->id = id; + threadPtr->done = 0; + threadPtr->waitedUpon = 0; threadPtr->threadMutex = (Tcl_Mutex) NULL; - threadPtr->cond = (Tcl_Condition) NULL; + threadPtr->cond = (Tcl_Condition) NULL; - Tcl_MutexLock(&joinMutex); + Tcl_MutexLock (&joinMutex); threadPtr->nextThreadPtr = firstThreadPtr; - firstThreadPtr = threadPtr; + firstThreadPtr = threadPtr; - Tcl_MutexUnlock(&joinMutex); + Tcl_MutexUnlock (&joinMutex); } /* @@ -250,9 +251,9 @@ TclRememberJoinableThread( * * TclSignalExitThread -- * - * This procedure signals that the specified thread is done with its - * work. If the thread is joinable this signal is propagated to the - * thread waiting upon it. + * This procedure signals that the specified thread is done with + * its work. If the thread is joinable this signal is propagated + * to the thread waiting upon it. * * Results: * None. @@ -263,54 +264,46 @@ TclRememberJoinableThread( *---------------------------------------------------------------------- */ -void -TclSignalExitThread( - Tcl_ThreadId id, /* Id of the thread signaling its exit. */ - int result) /* The result from the thread. */ +VOID +TclSignalExitThread(id,result) + Tcl_ThreadId id; /* Id of the thread signaling its exit */ + int result; /* The result from the thread */ { - JoinableThread *threadPtr; + JoinableThread* threadPtr; - Tcl_MutexLock(&joinMutex); + Tcl_MutexLock (&joinMutex); - threadPtr = firstThreadPtr; - while ((threadPtr != NULL) && (threadPtr->id != id)) { - threadPtr = threadPtr->nextThreadPtr; - } + for (threadPtr = firstThreadPtr; + (threadPtr != (JoinableThread*) NULL) && (threadPtr->id != id); + threadPtr = threadPtr->nextThreadPtr) + /* empty body */ + ; - if (threadPtr == NULL) { - /* - * Thread not found. Not joinable. No problem, nothing to do. + if (threadPtr == (JoinableThread*) NULL) { + /* Thread not found. Not joinable. No problem, nothing to do. */ - Tcl_MutexUnlock(&joinMutex); + Tcl_MutexUnlock (&joinMutex); return; } - /* - * Switch over the exclusive access from the list to the structure, then - * store the result, set the flag and notify the waiting thread, provided - * that it exists. The order of lock/unlock ensures that a thread entering - * 'TclJoinThread' will not interfere with us. + /* Switch over the exclusive access from the list to the structure, + * then store the result, set the flag and notify the waiting thread, + * provided that it exists. The order of lock/unlock ensures that a + * thread entering 'TclJoinThread' will not interfere with us. */ - Tcl_MutexLock(&threadPtr->threadMutex); - Tcl_MutexUnlock(&joinMutex); + Tcl_MutexLock (&threadPtr->threadMutex); + Tcl_MutexUnlock (&joinMutex); - threadPtr->done = 1; + threadPtr->done = 1; threadPtr->result = result; if (threadPtr->waitedUpon) { - Tcl_ConditionNotify(&threadPtr->cond); + Tcl_ConditionNotify (&threadPtr->cond); } - Tcl_MutexUnlock(&threadPtr->threadMutex); + Tcl_MutexUnlock (&threadPtr->threadMutex); } + #endif /* WIN32 */ - -/* - * Local Variables: - * mode: c - * c-basic-offset: 4 - * fill-column: 78 - * End: - */ |