2008-05-27 Neal H. Walfield <neal@gnu.org>

	* pthread/pt-internal.h (__pthread_queue_iterate): Before
	returning the current element, save its next pointer.
	(__pthread_dequeuing_iterate): Likewise.

	* sysdeps/l4/hurd/pt-wakeup.c (__pthread_wakeup): Loop until we
	successfully wake THREAD.

2 files changed, 29 insertions, 8 deletions

diff --git a/pthread/pt-internal.h b/pthread/pt-internal.h
index 41fbc830..853d739d 100644
--- a/pthread/pt-internal.h
+++ b/pthread/pt-internal.h
@@ -122,15 +122,22 @@ __pthread_dequeue (struct __pthread *thread)
 }
 
 /* Iterate over QUEUE storing each element in ELEMENT.  */
-#define __pthread_queue_iterate(queue, element) \
-	for (element = queue; element; element = element->next)
+#define __pthread_queue_iterate(queue, element)				\
+  for (struct __pthread *__pdi_next = (queue);				\
+       ((element) = __pdi_next)						\
+	 && ((__pdi_next = __pdi_next->next),				\
+	     true);							\
+       )
 
 /* Iterate over QUEUE dequeuing each element, storing it in
    ELEMENT.  */
-#define __pthread_dequeuing_iterate(queue, element) \
-	for (element = queue; \
-	     element && ((element->prevp = 0), 1); \
-	     element = element->next)
+#define __pthread_dequeuing_iterate(queue, element)			\
+  for (struct __pthread *__pdi_next = (queue);				\
+       ((element) = __pdi_next)						\
+	 && ((__pdi_next = __pdi_next->next),				\
+	     ((element)->prevp = 0),					\
+	     true);							\
+       )
 
 /* The total number of threads currently active.  */
 extern atomic_fast32_t __pthread_total;
diff --git a/sysdeps/l4/hurd/pt-wakeup.c b/sysdeps/l4/hurd/pt-wakeup.c
index 2225cca0..e568a6f9 100644
--- a/sysdeps/l4/hurd/pt-wakeup.c
+++ b/sysdeps/l4/hurd/pt-wakeup.c
@@ -27,6 +27,20 @@
 void
 __pthread_wakeup (struct __pthread *thread)
 {
-  long ret = futex_wake (&thread->threadid, INT_MAX);
-  assert (ret == 1);
+  /* We need to loop here as the blocked thread may not yet be
+     blocked!  Here's what happens when a thread blocks: it registers
+     itself as blocked, drops the relevant lock and then actually
+     blocks (via __pthread_block).  This means that after dropping the
+     lock and before blocking, it may be interrupted and another
+     thread may try to wake it.  */
+  long ret;
+  do
+    {
+      ret = futex_wake (&thread->threadid, INT_MAX);
+      assertx (ret <= 1, "tid: %x, ret: %d", thread->threadid, ret);
+
+      if (ret == 0)
+	l4_thread_switch (thread->threadid);
+    }
+  while (ret == 0);
 }