From 3ef98898333255b8000e9ab4801652c42fd5aacc Mon Sep 17 00:00:00 2001 From: rpj Date: Mon, 25 Apr 2005 14:42:37 +0000 Subject: '' --- pthread_once.c | 806 ++++++++++++++++++++++++++++----------------------------- 1 file changed, 403 insertions(+), 403 deletions(-) (limited to 'pthread_once.c') diff --git a/pthread_once.c b/pthread_once.c index fad9dcc..eb355dd 100644 --- a/pthread_once.c +++ b/pthread_once.c @@ -1,403 +1,403 @@ -/* - * 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 - */ - -/* - * NOTES: - * pthread_once() performs a very simple task. So why is this implementation - * so complicated? - * - * The original implementation WAS very simple, but it relied on Windows random - * priority boosting to resolve starvation problems. Windows priority boosting - * does not occur for realtime priority classes (levels 16 to 31). - * - * You can check back to previous versions of code in the CVS repository or - * search the mailing list archives for discussion. - * - * Version A - * --------- - * Waiting threads would resume and suspend again using Sleep(0) until the - * init_routine had completed, but a higher priority waiter could hog the CPU and - * starve the initter thread until Windows randomly boosted it's priority, or forever - * for realtime applications. - * - * Version B - * --------- - * This was fixed by introducing a per once_control manual-reset event that is - * created and destroyed dynamically only if there are waiters. The design did not - * need global critical sections. Each once_control remained independent. A waiter - * could be confident that if the event was not null then it did not need to create - * the event. - * - * Version C - * --------- - * Since a change in ABI would result from version B, it was decided to take - * the opportunity and make pthread_once() fully compliant with the Single Unix - * Specification (version 3 at the time). This required allowing the init_routine - * to be a cancelation point. A cancelation meant that at least some waiting threads - * if any had to be woken so that one might become the new initter thread. - * Waiters could no longer simply assume that, if the event was not null, it did - * not need to create an event. Some real critical sections were needed, and in the - * current library, a global CRITICAL_SECTION is probably more efficient than a per - * once_control PTHREAD_MUTEX_INITIALIZER that should be somehow destroyed on exit from - * pthread_once(). Also, the cancelled init thread needed to set the event, and the - * new init thread (the winner of the race between any newly arriving threads and - * waking waiters) would need to reset it again. In the meantime, threads could be - * happily looping around until they either suspended on the reset event, or exited - * because the init thread had completed. It was also once again possible for a higher - * priority waiter to starve the init thread. - * - * Version D - * --------- - * There were now two options considered: - * - use an auto-reset event; OR - * - add our own priority boosting. - * - * An auto-reset event would stop threads from looping ok, but it makes threads - * dependent on earlier threads to successfully set the event in turn when it's time - * to wake up, and this serialises threads unecessarily on MP systems. It also adds - * an extra kernel call for each waking thread. If one waiter wakes and dies (async - * cancelled or killed) before it can set the event, then all remaining waiters are - * stranded. - * - * Priority boosting is a standard method for solving priority inversion and - * starvation problems. Furthermore, all of the priority boost logic can - * be restricted to the post cancellation tracks. That is, it need not slow - * the normal cancel-free behaviour. Threads remain independent of other threads. - * - * The implementation below adds only a few local (to the thread) integer comparisons - * to the normal track through the routine and additional bus locking/cache line - * syncing operations have been avoided altogether in the uncontended track. - */ - -#include "pthread.h" -#include "implement.h" - - -static void PTW32_CDECL -ptw32_once_init_routine_cleanup(void * arg) -{ - pthread_once_t * once_control = (pthread_once_t *) arg; - - (void) PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->state, (LONG)PTW32_ONCE_CANCELLED); - (void) PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->started, (LONG)PTW32_FALSE); - -// EnterCriticalSection(&ptw32_once_event_lock); - if (InterlockedExchangeAdd((LPLONG)&once_control->event, 0L)) /* MBR fence */ - { - int lasterror = GetLastError (); - int lastWSAerror = WSAGetLastError (); - - /* - * There are waiters, wake some up. - */ - if (!SetEvent(once_control->event)) - { - SetLastError (lasterror); - WSASetLastError (lastWSAerror); - } - } -// LeaveCriticalSection(&ptw32_once_event_lock); -} - - -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; - int lasterror; - int lastWSAerror; - int restoreLastError; - LONG state; - pthread_t self; - HANDLE w32Thread = 0; - - if (once_control == NULL || init_routine == NULL) - { - result = EINVAL; - goto FAIL0; - } - else - { - result = 0; - } - - /* - * We want to be invisible to GetLastError() outside of this routine. - */ - lasterror = GetLastError (); - lastWSAerror = WSAGetLastError (); - restoreLastError = PTW32_FALSE; - - while (!((state = InterlockedExchangeAdd((LPLONG)&once_control->state, 0L)) /* Atomic Read */ - & (LONG)PTW32_ONCE_DONE)) - { - 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() from changing our priority while we're boosted. - */ - pthread_mutex_lock(&((ptw32_thread_t *)self.p)->threadLock); - SetThreadPriority(w32Thread, THREAD_PRIORITY_HIGHEST); - } - - if (!PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->started, (LONG)PTW32_TRUE)) - { - if (cancelled) - { - /* - * The previous initter was cancelled. - * We now have a new initter (us) and we need to make the rest wait again. - * Furthermore, we're running at max priority until after we've reset the event - * so we will not be starved by any other threads that may now be looping - * around. - */ -// EnterCriticalSection(&ptw32_once_event_lock); - if (InterlockedExchangeAdd((LPLONG)&once_control->event, 0L)) /* MBR fence */ - { - if (!ResetEvent(once_control->event)) - { - restoreLastError = PTW32_TRUE; - } - } -// LeaveCriticalSection(&ptw32_once_event_lock); - - /* - * Any threads entering the wait section and getting out again before - * the event is reset and the CANCELLED state is cleared will, at worst, - * just go around again or, if they suspend and we (the initter) completes before - * they resume, they will see state == DONE and leave immediately. - */ - PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->state, (LONG)PTW32_ONCE_CLEAR); - - /* - * Restore priority. We catch any changes to this thread's priority - * only if they were done through the POSIX API (i.e. pthread_setschedparam) - */ - SetThreadPriority(w32Thread, ((ptw32_thread_t *)self.p)->sched_priority); - 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 - - (void) PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->state, (LONG)PTW32_ONCE_DONE); - - /* - * we didn't create the event. - * it is only there if there is someone waiting. - * Avoid using the global event_lock but still prevent SetEvent - * from overwriting any 'lasterror' if the event is closed before we - * are done with it. - */ - if (InterlockedExchangeAdd((LPLONG)&once_control->event, 0L)) /* MBR fence */ - { - if (!SetEvent(once_control->event)) - { - restoreLastError = PTW32_TRUE; - } - } - } - else - { - HANDLE tmpEvent; - - if (cancelled) - { - /* - * Restore priority. We catch any changes to this thread's priority - * only if they were done through the POSIX API (i.e. pthread_setschedparam. - */ - SetThreadPriority(w32Thread, ((ptw32_thread_t *)self.p)->sched_priority); - pthread_mutex_unlock(&((ptw32_thread_t *)self.p)->threadLock); - } - - /* - * wait for init. - * while waiting, create an event to wait on - */ - -// EnterCriticalSection(&ptw32_once_event_lock); - if (1 == InterlockedIncrement((LPLONG)&once_control->eventUsers)) - { - /* - * RE CANCELLATION: - * If we are the first thread after the initter thread, and the init_routine is cancelled - * while we're suspended at this point in the code:- - * - state will not get set to PTW32_ONCE_DONE; - * - cleanup will not see an event and cannot set it; - * - therefore, we will eventually resume, create an event and wait on it; - * cleanup will set state == CANCELLED before checking for an event, so that - * we will see it and avoid waiting (as for state == DONE). We will go around again and - * we may then become the initter. - * If we are still the only other thread when we get to the end of this block, we will - * have closed the event (good). If another thread beats us to be initter, then we will - * re-enter here (good). In case the old event is reused, the event is always reset by - * the new initter before clearing the CANCELLED state, causing any threads that are - * cycling around the loop to wait again. - * The initter thread is guaranteed to be at equal or higher priority than any waiters - * so no waiters will starve the initter, which might otherwise cause us to loop - * forever. - */ - tmpEvent = CreateEvent(NULL, PTW32_TRUE, PTW32_FALSE, NULL); - if (PTW32_INTERLOCKED_COMPARE_EXCHANGE((PTW32_INTERLOCKED_LPLONG)&once_control->event, - (PTW32_INTERLOCKED_LONG)tmpEvent, - (PTW32_INTERLOCKED_LONG)0)) - { - CloseHandle(tmpEvent); - } - } -// LeaveCriticalSection(&ptw32_once_event_lock); - - /* - * Check 'state' again in case the initting thread has finished or cancelled - * and left before seeing that there was an event to trigger. - */ - - switch (InterlockedExchangeAdd((LPLONG)&once_control->state, 0L)) - { - case PTW32_ONCE_CLEAR: - { - /* Neither DONE nor CANCELLED */ - if (WAIT_FAILED == WaitForSingleObject(once_control->event, INFINITE)) - { - restoreLastError = PTW32_TRUE; - /* - * If the wait failed it's probably because the event is invalid. - * That's possible after a cancellation (but rare) if we got through the - * event create block above while a woken thread was suspended between - * the decrement and exchange below and then resumed before we could wait. - * So we'll yield. - */ - Sleep(0); - } - break; - } - case PTW32_ONCE_CANCELLED: - { - if (once_control->started) - { - /* The new initter hasn't cleared the cancellation yet, so give the - * processor to a more productive thread. */ - Sleep(0); - } - break; - } - } - - /* last one out shut off the lights */ -// EnterCriticalSection(&ptw32_once_event_lock); - if (0 == InterlockedDecrement((LPLONG)&once_control->eventUsers)) - { - /* we were last */ - if ((tmpEvent = (HANDLE) - PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->event, - (LONG)0))) - { - CloseHandle(tmpEvent); - } - } -// LeaveCriticalSection(&ptw32_once_event_lock); - } - } - - if (restoreLastError) - { - SetLastError (lasterror); - WSASetLastError (lastWSAerror); - } - - /* - * ------------ - * 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 + */ + +/* + * NOTES: + * pthread_once() performs a very simple task. So why is this implementation + * so complicated? + * + * The original implementation WAS very simple, but it relied on Windows random + * priority boosting to resolve starvation problems. Windows priority boosting + * does not occur for realtime priority classes (levels 16 to 31). + * + * You can check back to previous versions of code in the CVS repository or + * search the mailing list archives for discussion. + * + * Version A + * --------- + * Waiting threads would resume and suspend again using Sleep(0) until the + * init_routine had completed, but a higher priority waiter could hog the CPU and + * starve the initter thread until Windows randomly boosted it's priority, or forever + * for realtime applications. + * + * Version B + * --------- + * This was fixed by introducing a per once_control manual-reset event that is + * created and destroyed dynamically only if there are waiters. The design did not + * need global critical sections. Each once_control remained independent. A waiter + * could be confident that if the event was not null then it did not need to create + * the event. + * + * Version C + * --------- + * Since a change in ABI would result from version B, it was decided to take + * the opportunity and make pthread_once() fully compliant with the Single Unix + * Specification (version 3 at the time). This required allowing the init_routine + * to be a cancelation point. A cancelation meant that at least some waiting threads + * if any had to be woken so that one might become the new initter thread. + * Waiters could no longer simply assume that, if the event was not null, it did + * not need to create an event. Some real critical sections were needed, and in the + * current library, a global CRITICAL_SECTION is probably more efficient than a per + * once_control PTHREAD_MUTEX_INITIALIZER that should be somehow destroyed on exit from + * pthread_once(). Also, the cancelled init thread needed to set the event, and the + * new init thread (the winner of the race between any newly arriving threads and + * waking waiters) would need to reset it again. In the meantime, threads could be + * happily looping around until they either suspended on the reset event, or exited + * because the init thread had completed. It was also once again possible for a higher + * priority waiter to starve the init thread. + * + * Version D + * --------- + * There were now two options considered: + * - use an auto-reset event; OR + * - add our own priority boosting. + * + * An auto-reset event would stop threads from looping ok, but it makes threads + * dependent on earlier threads to successfully set the event in turn when it's time + * to wake up, and this serialises threads unecessarily on MP systems. It also adds + * an extra kernel call for each waking thread. If one waiter wakes and dies (async + * cancelled or killed) before it can set the event, then all remaining waiters are + * stranded. + * + * Priority boosting is a standard method for solving priority inversion and + * starvation problems. Furthermore, all of the priority boost logic can + * be restricted to the post cancellation tracks. That is, it need not slow + * the normal cancel-free behaviour. Threads remain independent of other threads. + * + * The implementation below adds only a few local (to the thread) integer comparisons + * to the normal track through the routine and additional bus locking/cache line + * syncing operations have been avoided altogether in the uncontended track. + */ + +#include "pthread.h" +#include "implement.h" + + +static void PTW32_CDECL +ptw32_once_init_routine_cleanup(void * arg) +{ + pthread_once_t * once_control = (pthread_once_t *) arg; + + (void) PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->state, (LONG)PTW32_ONCE_CANCELLED); + (void) PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->started, (LONG)PTW32_FALSE); + +// EnterCriticalSection(&ptw32_once_event_lock); + if (InterlockedExchangeAdd((LPLONG)&once_control->event, 0L)) /* MBR fence */ + { + int lasterror = GetLastError (); + int lastWSAerror = WSAGetLastError (); + + /* + * There are waiters, wake some up. + */ + if (!SetEvent(once_control->event)) + { + SetLastError (lasterror); + WSASetLastError (lastWSAerror); + } + } +// LeaveCriticalSection(&ptw32_once_event_lock); +} + + +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; + int lasterror; + int lastWSAerror; + int restoreLastError; + LONG state; + pthread_t self; + HANDLE w32Thread = 0; + + if (once_control == NULL || init_routine == NULL) + { + result = EINVAL; + goto FAIL0; + } + else + { + result = 0; + } + + /* + * We want to be invisible to GetLastError() outside of this routine. + */ + lasterror = GetLastError (); + lastWSAerror = WSAGetLastError (); + restoreLastError = PTW32_FALSE; + + while (!((state = InterlockedExchangeAdd((LPLONG)&once_control->state, 0L)) /* Atomic Read */ + & (LONG)PTW32_ONCE_DONE)) + { + 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() from changing our priority while we're boosted. + */ + pthread_mutex_lock(&((ptw32_thread_t *)self.p)->threadLock); + SetThreadPriority(w32Thread, THREAD_PRIORITY_HIGHEST); + } + + if (!PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->started, (LONG)PTW32_TRUE)) + { + if (cancelled) + { + /* + * The previous initter was cancelled. + * We now have a new initter (us) and we need to make the rest wait again. + * Furthermore, we're running at max priority until after we've reset the event + * so we will not be starved by any other threads that may now be looping + * around. + */ +// EnterCriticalSection(&ptw32_once_event_lock); + if (InterlockedExchangeAdd((LPLONG)&once_control->event, 0L)) /* MBR fence */ + { + if (!ResetEvent(once_control->event)) + { + restoreLastError = PTW32_TRUE; + } + } +// LeaveCriticalSection(&ptw32_once_event_lock); + + /* + * Any threads entering the wait section and getting out again before + * the event is reset and the CANCELLED state is cleared will, at worst, + * just go around again or, if they suspend and we (the initter) completes before + * they resume, they will see state == DONE and leave immediately. + */ + PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->state, (LONG)PTW32_ONCE_CLEAR); + + /* + * Restore priority. We catch any changes to this thread's priority + * only if they were done through the POSIX API (i.e. pthread_setschedparam) + */ + SetThreadPriority(w32Thread, ((ptw32_thread_t *)self.p)->sched_priority); + 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 + + (void) PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->state, (LONG)PTW32_ONCE_DONE); + + /* + * we didn't create the event. + * it is only there if there is someone waiting. + * Avoid using the global event_lock but still prevent SetEvent + * from overwriting any 'lasterror' if the event is closed before we + * are done with it. + */ + if (InterlockedExchangeAdd((LPLONG)&once_control->event, 0L)) /* MBR fence */ + { + if (!SetEvent(once_control->event)) + { + restoreLastError = PTW32_TRUE; + } + } + } + else + { + HANDLE tmpEvent; + + if (cancelled) + { + /* + * Restore priority. We catch any changes to this thread's priority + * only if they were done through the POSIX API (i.e. pthread_setschedparam. + */ + SetThreadPriority(w32Thread, ((ptw32_thread_t *)self.p)->sched_priority); + pthread_mutex_unlock(&((ptw32_thread_t *)self.p)->threadLock); + } + + /* + * wait for init. + * while waiting, create an event to wait on + */ + +// EnterCriticalSection(&ptw32_once_event_lock); + if (1 == InterlockedIncrement((LPLONG)&once_control->eventUsers)) + { + /* + * RE CANCELLATION: + * If we are the first thread after the initter thread, and the init_routine is cancelled + * while we're suspended at this point in the code:- + * - state will not get set to PTW32_ONCE_DONE; + * - cleanup will not see an event and cannot set it; + * - therefore, we will eventually resume, create an event and wait on it; + * cleanup will set state == CANCELLED before checking for an event, so that + * we will see it and avoid waiting (as for state == DONE). We will go around again and + * we may then become the initter. + * If we are still the only other thread when we get to the end of this block, we will + * have closed the event (good). If another thread beats us to be initter, then we will + * re-enter here (good). In case the old event is reused, the event is always reset by + * the new initter before clearing the CANCELLED state, causing any threads that are + * cycling around the loop to wait again. + * The initter thread is guaranteed to be at equal or higher priority than any waiters + * so no waiters will starve the initter, which might otherwise cause us to loop + * forever. + */ + tmpEvent = CreateEvent(NULL, PTW32_TRUE, PTW32_FALSE, NULL); + if (PTW32_INTERLOCKED_COMPARE_EXCHANGE((PTW32_INTERLOCKED_LPLONG)&once_control->event, + (PTW32_INTERLOCKED_LONG)tmpEvent, + (PTW32_INTERLOCKED_LONG)0)) + { + CloseHandle(tmpEvent); + } + } +// LeaveCriticalSection(&ptw32_once_event_lock); + + /* + * Check 'state' again in case the initting thread has finished or cancelled + * and left before seeing that there was an event to trigger. + */ + + switch (InterlockedExchangeAdd((LPLONG)&once_control->state, 0L)) + { + case PTW32_ONCE_CLEAR: + { + /* Neither DONE nor CANCELLED */ + if (WAIT_FAILED == WaitForSingleObject(once_control->event, INFINITE)) + { + restoreLastError = PTW32_TRUE; + /* + * If the wait failed it's probably because the event is invalid. + * That's possible after a cancellation (but rare) if we got through the + * event create block above while a woken thread was suspended between + * the decrement and exchange below and then resumed before we could wait. + * So we'll yield. + */ + Sleep(0); + } + break; + } + case PTW32_ONCE_CANCELLED: + { + if (once_control->started) + { + /* The new initter hasn't cleared the cancellation yet, so give the + * processor to a more productive thread. */ + Sleep(0); + } + break; + } + } + + /* last one out shut off the lights */ +// EnterCriticalSection(&ptw32_once_event_lock); + if (0 == InterlockedDecrement((LPLONG)&once_control->eventUsers)) + { + /* we were last */ + if ((tmpEvent = (HANDLE) + PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->event, + (LONG)0))) + { + CloseHandle(tmpEvent); + } + } +// LeaveCriticalSection(&ptw32_once_event_lock); + } + } + + if (restoreLastError) + { + SetLastError (lasterror); + WSASetLastError (lastWSAerror); + } + + /* + * ------------ + * Failure Code + * ------------ + */ +FAIL0: + return (result); + +} /* pthread_once */ -- cgit v1.2.3