diff options
Diffstat (limited to 'pthread_once.c')
| -rw-r--r-- | pthread_once.c | 482 |
1 files changed, 241 insertions, 241 deletions
diff --git a/pthread_once.c b/pthread_once.c index 9bcd975..62b412c 100644 --- a/pthread_once.c +++ b/pthread_once.c @@ -1,241 +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.
- *
- * 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 */
+/* + * 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 */ |