Update.

2001-05-01  Kaz Kylheku  <kaz@ashi.footprints.net>

	Memory barrier overhaul following line by line inspection.
	* mutex.c (pthread_once): Missing memory barriers added.
	* pthread.c (__pthread_wait_for_restart_signal,
	__pthread_timedsuspend_new, __pthread_restart_new): Added
	memory barriers ``just in case'' and for documentary value.
	* spinlock.c (__pthread_release): New inline function for releasing
	spinlock, to complement __pthread_acquire.  Includes memory
	barrier prior to assignment to spinlock, and __asm __volatile
	dance to prevent reordering or optimization of the spinlock access.
	* spinlock.c (__pthread_unlock, __pthread_alt_lock,
	__pthread_alt_timedlock, __pthread_alt_unlock,
	__pthread_compare_and_swap): Updated to use new __pthread_release
	instead of updating spinlock directly.
	* spinlock.c (__pthread_lock, __pthread_unlock, wait_node_alloc,
	wait_node_free, wait_node_dequeue, __pthread_alt_lock,
	__pthread_alt_timedlock, __pthread_alt_unlock, __pthread_acquire):
	Memory barrier overhaul.  Lots of missing memory barriers added,
	a couple needless ones removed.
	* spinlock.c (__pthread_compare_and_swap): testandset optimization
	removed, just calls __pthread_acquire, which has the new read
	barrier in it before its testandset.

1 files changed, 5 insertions, 1 deletions

diff --git a/linuxthreads/mutex.c b/linuxthreads/mutex.c
index 3ad27942af..3c97ea7d66 100644
--- a/linuxthreads/mutex.c
+++ b/linuxthreads/mutex.c
@@ -285,7 +285,10 @@ int __pthread_once(pthread_once_t * once_control, void (*init_routine)(void))
   int state_changed;
 
   /* Test without locking first for speed */
-  if (*once_control == DONE) return 0;
+  if (*once_control == DONE) {
+    READ_MEMORY_BARRIER();
+    return 0;
+  }
   /* Lock and test again */
 
   state_changed = 0;
@@ -310,6 +313,7 @@ int __pthread_once(pthread_once_t * once_control, void (*init_routine)(void))
     init_routine();
     pthread_cleanup_pop(0);
     pthread_mutex_lock(&once_masterlock);
+    WRITE_MEMORY_BARRIER();
     *once_control = DONE;
     state_changed = 1;
   }