* [PATCH] Add write barrier into pthread_cancel_init
@ 2005-11-16 23:19 Jakub Jelinek
0 siblings, 0 replies; only message in thread
From: Jakub Jelinek @ 2005-11-16 23:19 UTC (permalink / raw)
To: Ulrich Drepper; +Cc: Glibc hackers
Hi!
If the compiler and/or processor reorders the writes to libgcc_s_*
variables in pthread_cancel_init, pthread_cancel_init might return early
if libgcc_s_getcfa has been already written, but some other libgcc_s_*
pointer the caller is actually interested in has not been written yet.
2005-11-17 Jakub Jelinek <jakub@redhat.com>
* sysdeps/pthread/unwind-forcedunwind.c (pthread_cancel_init): Put
a write barrier before writing libgcc_s_getcfa.
--- libc/nptl/sysdeps/pthread/unwind-forcedunwind.c.jj 2003-09-04 07:41:57.000000000 +0200
+++ libc/nptl/sysdeps/pthread/unwind-forcedunwind.c 2005-11-17 00:13:37.000000000 +0100
@@ -1,4 +1,4 @@
-/* Copyright (C) 2003 Free Software Foundation, Inc.
+/* Copyright (C) 2003, 2005 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Jakub Jelinek <jakub@redhat.com>.
@@ -56,6 +56,10 @@ pthread_cancel_init (void)
libgcc_s_resume = resume;
libgcc_s_personality = personality;
libgcc_s_forcedunwind = forcedunwind;
+ /* Make sure libgcc_s_getcfa is written last. Otherwise,
+ pthread_cancel_init might return early even when the pointer the
+ caller is interested in is not initialized yet. */
+ atomic_write_barrier ();
libgcc_s_getcfa = getcfa;
}
Jakub
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