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authorPaul E. Murphy <murphyp@linux.vnet.ibm.com>2016-01-11 17:24:04 -0500
committerTulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com>2016-01-15 16:53:08 -0200
commita3e5b4feeb54cb92657ec2bc6d9be1fcef9e8575 (patch)
treef538c5cf1a10d4d8ec7821cf086df977d5dc8ea3
parent692de4b3960dc90bdcfb871513ee4d81d314cf69 (diff)
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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.
-rw-r--r--ChangeLog5
-rw-r--r--rt/tst-mqueue5.c21
2 files changed, 24 insertions, 2 deletions
diff --git a/ChangeLog b/ChangeLog
index 7f2a19d50a..fb5cd0e024 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2016-01-15  Paul E. Murphy  <murphyp@linux.vnet.ibm.com>
+
+	* rt/tst-mqueue5.c (thr): Cleanup misleading comment.
+	(do_child): Mask SIGRTMIN while thr 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 aa74fa31ac..25042bcc9f 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)
     {