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authorUlrich Drepper <drepper@redhat.com>2009-05-15 20:42:36 -0700
committerUlrich Drepper <drepper@redhat.com>2009-05-15 20:42:36 -0700
commit9437b427cec6266abd303983848549a5c4ba0d0a (patch)
tree7d3c7df6abb9a33d4f35a3dc20baa59ff1a53ea1 /nptl/pthread_cancel.c
parentbbc5d74dd0bd1c3dbe7ea8515f081dc7e318272c (diff)
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Fix change to prevent cancel signal in unsafe places.
The bits tested to decide when to delay the return when switching
off async cancel mode were wrong.  Fix that.  Also close a race
condition in pthread_cancel where the bit indicating the cancellation
is unconditionally set even if the cancel type might have changed.
Diffstat (limited to 'nptl/pthread_cancel.c')
-rw-r--r--nptl/pthread_cancel.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/nptl/pthread_cancel.c b/nptl/pthread_cancel.c
index a13af56b37..55bb0da922 100644
--- a/nptl/pthread_cancel.c
+++ b/nptl/pthread_cancel.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.
+/* Copyright (C) 2002, 2003, 2004, 2009 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
 
@@ -44,6 +44,7 @@ pthread_cancel (th)
   int newval;
   do
     {
+    again:
       oldval = pd->cancelhandling;
       newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;
 
@@ -59,7 +60,10 @@ pthread_cancel (th)
       if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
 	{
 	  /* Mark the cancellation as "in progress".  */
-	  atomic_bit_set (&pd->cancelhandling, CANCELING_BIT);
+	  if (atomic_compare_and_exchange_bool_acq (&pd->cancelhandling,
+						    oldval | CANCELING_BITMASK,
+						    oldval))
+	    goto again;
 
 	  /* The cancellation handler will take care of marking the
 	     thread as canceled.  */