1 files changed, 241 insertions, 182 deletions
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 */