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authorrpj <rpj>2005-06-03 08:32:43 +0000
committerrpj <rpj>2005-06-03 08:32:43 +0000
commit15f1b0bc1f4feeca60ca1dda769928822d6c032a (patch)
tree26a3693fd7058745a2bd76e8c086dc4d16656049 /pthread_once.c
parent1908d93b42b01cea49c886e2260fd70ac05becf7 (diff)
''
Diffstat (limited to 'pthread_once.c')
-rw-r--r--pthread_once.c187
1 files changed, 16 insertions, 171 deletions
diff --git a/pthread_once.c b/pthread_once.c
index 62b412c..efcfd0f 100644
--- a/pthread_once.c
+++ b/pthread_once.c
@@ -38,204 +38,49 @@
#include "implement.h"
-static void
-ptw32_once_init_routine_cleanup(void * arg)
+static void PTW32_CDECL
+ptw32_once_on_init_cancel (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);
+ /* when the initting thread is cancelled we have to release the lock */
+ ptw32_mcs_local_node_t *node = (ptw32_mcs_local_node_t *)arg;
+ ptw32_mcs_lock_release(node);
}
-
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;
+ return EINVAL;
}
-
- /*
- * 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))
+
+ if (InterlockedExchangeAdd((LPLONG)&once_control->done, 0L)) /* MBR fence */
{
- /*
- * 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);
+ ptw32_mcs_local_node_t node;
- 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);
- }
+ ptw32_mcs_lock_acquire((ptw32_mcs_lock_t *)&once_control->lock, &node);
- if (PTW32_INTERLOCKED_EXCHANGE((LPLONG) &once_control->started, 0L) == -1)
+ if (InterlockedExchangeAdd((LPLONG)&once_control->done, 0L))
{
- 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_push(ptw32_once_on_init_cancel, (void *)&node);
+ (*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);
+ (void) PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->done, 0L);
}
- 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);
- }
+ ptw32_mcs_lock_release(&node);
}
- /*
- * Fall through Intentionally
- */
-
- /*
- * ------------
- * Failure Code
- * ------------
- */
-FAIL0:
- return (result);
+ return 0;
} /* pthread_once */