From e1fba251064eecf4cdfd63723aadb5df9174ddfe Mon Sep 17 00:00:00 2001 From: rpj Date: Tue, 12 Apr 2005 06:35:52 +0000 Subject: '' --- pthread_once.c | 423 ++++++++++++++++++++++++++++++++------------------------- 1 file changed, 241 insertions(+), 182 deletions(-) (limited to 'pthread_once.c') diff --git a/pthread_once.c b/pthread_once.c index 73fea33..9bcd975 100644 --- a/pthread_once.c +++ b/pthread_once.c @@ -1,182 +1,241 @@ -/* - * pthread_once.c - * - * Description: - * This translation unit implements miscellaneous thread functions. - * - * -------------------------------------------------------------------------- - * - * Pthreads-win32 - POSIX Threads Library for Win32 - * Copyright(C) 1998 John E. Bossom - * Copyright(C) 1999,2005 Pthreads-win32 contributors - * - * Contact Email: rpj@callisto.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 - */ - -#include "pthread.h" -#include "implement.h" - - -static void -ptw32_once_init_routine_cleanup(void * arg) -{ - pthread_once_t * once_control = (pthread_once_t *) arg; - - (void) pthread_mutex_lock(&ptw32_once_control.mtx); - once_control->done = PTW32_ONCE_CANCELLED; - (void) PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->started, -1L); - /* - * Wake everyone up. - * - * Holding the mutex during the broadcast prevents threads being left - * behind waiting. - */ - (void) pthread_cond_broadcast(&ptw32_once_control.cond); - (void) pthread_mutex_unlock(&ptw32_once_control.mtx); -} - - -int -pthread_once (pthread_once_t * once_control, void (*init_routine) (void)) - /* - * ------------------------------------------------------ - * DOCPUBLIC - * If any thread in a process with a once_control parameter - * makes a call to pthread_once(), the first call will summon - * the init_routine(), but subsequent calls will not. The - * once_control parameter determines whether the associated - * initialization routine has been called. The init_routine() - * is complete upon return of pthread_once(). - * This function guarantees that one and only one thread - * executes the initialization routine, init_routine when - * access is controlled by the pthread_once_t control - * key. - * - * PARAMETERS - * once_control - * pointer to an instance of pthread_once_t - * - * init_routine - * pointer to an initialization routine - * - * - * DESCRIPTION - * See above. - * - * RESULTS - * 0 success, - * EINVAL once_control or init_routine is NULL - * - * ------------------------------------------------------ - */ -{ - int result; - - if (once_control == NULL || init_routine == NULL) - { - - result = EINVAL; - goto FAIL0; - - } - else - { - result = 0; - } - - /* - * Use a single global cond+mutex to manage access to all once_control objects. - * Unlike a global mutex on it's own, the global cond+mutex allows faster - * once_controls to overtake slower ones. Spurious wakeups may occur, but - * can be tolerated. - * - * To maintain a separate mutex for each once_control object requires either - * cleaning up the mutex (difficult to synchronise reliably), or leaving it - * around forever. Since we can't make assumptions about how an application might - * employ pthread_once objects, the later is considered to be unacceptable. - * - * Since this is being introduced as a bug fix, the global cond+mtx also avoids - * a change in the ABI, maintaining backwards compatibility. - */ - - while (!(InterlockedExchangeAdd((LPLONG)&once_control->done, 0L) /* Full mem barrier read */ - & PTW32_ONCE_DONE)) - { - if (PTW32_INTERLOCKED_EXCHANGE((LPLONG) &once_control->started, 0L) == -1) - { - /* In case the previous initter was cancelled, reset cancelled state */ - (void) pthread_mutex_lock(&ptw32_once_control.mtx); - once_control->done = PTW32_ONCE_CLEAR; - (void) pthread_mutex_unlock(&ptw32_once_control.mtx); - -#ifdef _MSC_VER -#pragma inline_depth(0) -#endif - - pthread_cleanup_push(ptw32_once_init_routine_cleanup, (void*) once_control); - (*init_routine) (); - pthread_cleanup_pop(0); - -#ifdef _MSC_VER -#pragma inline_depth() -#endif - - /* - * Holding the mutex during the broadcast prevents threads being left - * behind waiting. - */ - (void) pthread_mutex_lock(&ptw32_once_control.mtx); - once_control->done = PTW32_ONCE_DONE; - (void) pthread_cond_broadcast(&ptw32_once_control.cond); - (void) pthread_mutex_unlock(&ptw32_once_control.mtx); - } - else - { - int oldCancelState; - - pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldCancelState); - (void) pthread_mutex_lock(&ptw32_once_control.mtx); - while (!once_control->done) - { - /* Neither DONE nor CANCELLED */ - (void) pthread_cond_wait(&ptw32_once_control.cond, &ptw32_once_control.mtx); - } - (void) pthread_mutex_unlock(&ptw32_once_control.mtx); - pthread_setcancelstate(oldCancelState, NULL); - } - } - - /* - * Fall through Intentionally - */ - - /* - * ------------ - * Failure Code - * ------------ - */ -FAIL0: - return (result); - -} /* pthread_once */ +/* + * pthread_once.c + * + * Description: + * This translation unit implements miscellaneous thread functions. + * + * -------------------------------------------------------------------------- + * + * Pthreads-win32 - POSIX Threads Library for Win32 + * Copyright(C) 1998 John E. Bossom + * Copyright(C) 1999,2005 Pthreads-win32 contributors + * + * Contact Email: rpj@callisto.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 + */ + +#include "pthread.h" +#include "implement.h" + + +static void +ptw32_once_init_routine_cleanup(void * arg) +{ + pthread_once_t * once_control = (pthread_once_t *) arg; + + (void) pthread_mutex_lock(&ptw32_once_control.mtx); + once_control->done = PTW32_ONCE_CANCELLED; + (void) PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->started, -1L); + /* + * Wake everyone up. + * + * Holding the mutex during the broadcast prevents threads being left + * behind waiting. + */ + (void) pthread_cond_broadcast(&ptw32_once_control.cond); + (void) pthread_mutex_unlock(&ptw32_once_control.mtx); +} + + +int +pthread_once (pthread_once_t * once_control, void (*init_routine) (void)) + /* + * ------------------------------------------------------ + * DOCPUBLIC + * If any thread in a process with a once_control parameter + * makes a call to pthread_once(), the first call will summon + * the init_routine(), but subsequent calls will not. The + * once_control parameter determines whether the associated + * initialization routine has been called. The init_routine() + * is complete upon return of pthread_once(). + * This function guarantees that one and only one thread + * executes the initialization routine, init_routine when + * access is controlled by the pthread_once_t control + * key. + * + * pthread_once() is not a cancelation point, but the init_routine + * can be. If it's cancelled then the effect on the once_control is + * as if pthread_once had never been entered. + * + * PARAMETERS + * once_control + * pointer to an instance of pthread_once_t + * + * init_routine + * pointer to an initialization routine + * + * + * DESCRIPTION + * See above. + * + * RESULTS + * 0 success, + * EINVAL once_control or init_routine is NULL + * + * ------------------------------------------------------ + */ +{ + int result; + LONG state; + pthread_t self; + HANDLE w32Thread = 0; + + if (once_control == NULL || init_routine == NULL) + { + + result = EINVAL; + goto FAIL0; + + } + else + { + result = 0; + } + + /* + * Use a single global cond+mutex to manage access to all once_control objects. + * Unlike a global mutex on it's own, the global cond+mutex allows faster + * once_controls to overtake slower ones. Spurious wakeups may occur, but + * can be tolerated. + * + * Since this is being introduced as a bug fix, the global cond+mtx also avoids + * a change in the ABI, maintaining backwards compatibility. + * + * To maintain a separate mutex for each once_control object requires either + * cleaning up the mutex (difficult to synchronise reliably), or leaving it + * around forever. Since we can't make assumptions about how an application might + * employ pthread_once objects, the later is considered to be unacceptable. + * + * once_control->done is now a multipurpose flag. It indicates either that + * the init_routine has been completed, or the thread running it has been cancelled. + * + * Priority boosting is used to ensure that the init_routine thread is not + * starved, by higher priority threads inside the while loop, before it can + * clear the cancelled flag. The init_routine will be run at the thread's + * normal base priority. Note that priority boosting is momentary, independent + * for each once_control, and occurs only AFTER an init_routine cancellation. + */ + + while (!((state = InterlockedExchangeAdd((LPLONG)&once_control->done, 0L)) /* Full mem barrier read */ + & PTW32_ONCE_DONE)) + { + /* + * Keep a per thread record of the cancelled state for speed. If the + * once_control state changes before we've finished with our local copy + * then no harm is done - in fact, we need it to complete the full priority + * boost transaction. + */ + LONG cancelled = (state & PTW32_ONCE_CANCELLED); + + if (cancelled) + { + /* Boost priority momentarily */ + if (!w32Thread) + { + self = pthread_self(); + w32Thread = ((ptw32_thread_t *)self.p)->threadH; + } + /* Prevent pthread_setschedparam() changing our priority while we're boosted. */ + (void) pthread_mutex_lock(&((ptw32_thread_t *)self.p)->threadLock); + SetThreadPriority(w32Thread, THREAD_PRIORITY_HIGHEST); + } + + if (PTW32_INTERLOCKED_EXCHANGE((LPLONG) &once_control->started, 0L) == -1) + { + if (cancelled) + { + /* Reset cancelled state */ + (void) pthread_mutex_lock(&ptw32_once_control.mtx); + once_control->done = PTW32_ONCE_CLEAR; + (void) pthread_mutex_unlock(&ptw32_once_control.mtx); + + /* + * Restore priority - any priority changes since the thread was created + * will be applied only if they were made via POSIX (i.e. pthread_setschedparam). + */ + SetThreadPriority(w32Thread, ((ptw32_thread_t *)self.p)->sched_priority); + (void) pthread_mutex_unlock(&((ptw32_thread_t *)self.p)->threadLock); + } + +#ifdef _MSC_VER +#pragma inline_depth(0) +#endif + + pthread_cleanup_push(ptw32_once_init_routine_cleanup, (void*) once_control); + (*init_routine) (); + pthread_cleanup_pop(0); + +#ifdef _MSC_VER +#pragma inline_depth() +#endif + + /* + * Holding the mutex during the broadcast prevents threads being left + * behind waiting. + */ + (void) pthread_mutex_lock(&ptw32_once_control.mtx); + once_control->done = PTW32_ONCE_DONE; + (void) pthread_cond_broadcast(&ptw32_once_control.cond); + (void) pthread_mutex_unlock(&ptw32_once_control.mtx); + } + else + { + int oldCancelState; + + if (cancelled) + { + /* + * Restore priority - any priority changes since the thread was created + * will be applied only if they were made via POSIX (i.e. pthread_setschedparam). + */ + SetThreadPriority(w32Thread, ((ptw32_thread_t *)self.p)->sched_priority); + (void) pthread_mutex_unlock(&((ptw32_thread_t *)self.p)->threadLock); + } + + pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldCancelState); + (void) pthread_mutex_lock(&ptw32_once_control.mtx); + while (!once_control->done /* Neither DONE nor CANCELLED */ + || (!(once_control->done & PTW32_ONCE_DONE) + && cancelled) /* Stop after one init_routine re-contest */) + { + cancelled = 0; + (void) pthread_cond_wait(&ptw32_once_control.cond, &ptw32_once_control.mtx); + } + (void) pthread_mutex_unlock(&ptw32_once_control.mtx); + pthread_setcancelstate(oldCancelState, NULL); + } + } + + /* + * Fall through Intentionally + */ + + /* + * ------------ + * Failure Code + * ------------ + */ +FAIL0: + return (result); + +} /* pthread_once */ -- cgit v1.2.3