Re: Tests Failures on PPC64

[Jan Kratochvil]

On Wed, 09 Dec 2009 19:31:52 +0100, Oleg Nesterov wrote:
> Hmm. it is obvioulsy racy, "static volatile unsigned started"
> is not atomic and thus the main thread can hang doing
> 
>       while (started < THREADS);
> 
> not that I think this explains the failure though.

Thanks, fixed (but the problem is not reproducible for me).


Regards,
Jan


--- ppc-dabr-race.c     8 Dec 2008 18:23:41 -0000       1.8
+++ ppc-dabr-race.c     14 Dec 2009 12:03:49 -0000      1.9
@@ -141,13 +141,14 @@ handler_fail (int signo)
   assert (0);
 }
 
+/* STARTED requires atomic access.  */
 static volatile unsigned started;
 
 static void *child_thread (void *data)
 {
   pid_t tid = gettid ();
 
-  started++;
+  __sync_add_and_fetch (&started, 1);
 
   /* We should stay in the syscall - better race probability.  */
   sleep (1);
@@ -178,7 +179,7 @@ static void child_func (void)
       assert (i == 0);
     }
 
-  while (started < THREADS);
+  while (__sync_add_and_fetch (&started, 0) < THREADS);
 
   l = ptrace (PTRACE_TRACEME, 0, NULL, NULL);
   assert (l == 0);