commit a3e5b4feeb54cb92657ec2bc6d9be1fcef9e8575
Author: Paul E. Murphy <murphyp@linux.vnet.ibm.com>
Date:   Mon Jan 11 17:24:04 2016 -0500

    Fix race in tst-mqueue5
    
    The check is done on line 117 by a thread spawned
    from do_child(), forked from do_test().  This test
    generates a signal in the forked process.
    
    Either thread may handle the signal, and on ppc,
    it happens to be done on do_child, on the thread
    which is not doing the check on line 117.
    
    This exposes a race condition whereby the test
    incorrectly fails as the signal is caught during
    or after the check.
    
    This is mitigated by ensuring the signal is blocked
    in the child thread while thread is running.

 2016-01-15  Martin Sebor  <msebor@redhat.com>
 
 	[BZ #19432]
diff --git a/rt/tst-mqueue5.c b/rt/tst-mqueue5.c
index aa74fa3..25042bc 100644
--- a/rt/tst-mqueue5.c
+++ b/rt/tst-mqueue5.c
@@ -116,7 +116,7 @@ thr (void *arg)
 
   if (rtmin_cnt != 2)
     {
-      puts ("SIGRTMIN signal in child did not arrive");
+      puts ("SIGRTMIN signal in thread did not arrive");
       result = 1;
     }
   else if (rtmin_pid != getppid ()
@@ -403,6 +403,16 @@ do_child (const char *name, pthread_barrier_t *b2, pthread_barrier_t *b3,
       result = 1;
     }
 
+  /* Ensure the thr thread gets the signal, not us.  */
+  sigset_t set;
+  sigemptyset (&set);
+  sigaddset (&set, SIGRTMIN);
+  if (pthread_sigmask (SIG_BLOCK, &set, NULL))
+    {
+      printf ("Failed to block SIGRTMIN in child: %m\n");
+      result = 1;
+    }
+
   (void) pthread_barrier_wait (b2);
 
   /* Parent calls mqsend (q), which should wake up mqrecv (q)
@@ -514,7 +524,14 @@ do_child (const char *name, pthread_barrier_t *b2, pthread_barrier_t *b3,
       result = 1;
     }
 
- void *thr_ret;
+  /* Reenable test signals before cleaning up the thread.  */
+  if (pthread_sigmask (SIG_UNBLOCK, &set, NULL))
+    {
+      printf ("Failed to unblock SIGRTMIN in child: %m\n");
+      result = 1;
+    }
+
+  void *thr_ret;
   ret = pthread_join (th, &thr_ret);
   if (ret)
     {