''

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 */