[tip:perfcounters/urgent] x86: atomic64: Fix unclean type use in atomic64_xchg()

[tip-bot for Ingo Molnar]

Commit-ID:  199e23780a7e75c63a9e3d1108804e3af450ea3e
Gitweb:     http://git.kernel.org/tip/199e23780a7e75c63a9e3d1108804e3af450ea3e
Author:     Ingo Molnar <mingo@xxxxxxx>
AuthorDate: Fri, 3 Jul 2009 13:02:39 +0200
Committer:  Ingo Molnar <mingo@xxxxxxx>
CommitDate: Fri, 3 Jul 2009 13:26:46 +0200

x86: atomic64: Fix unclean type use in atomic64_xchg()

Linus noticed that atomic64_xchg() uses atomic_read(), which
happens to work because atomic_read() is a macro so the
.counter value gets u64-read on 32-bit too - but this is really
bogus and serious bugs are waiting to happen.

Fix atomic64_xchg() to use __atomic64_read() instead.

No code changed:

arch/x86/lib/atomic64_32.o:

   text	   data	    bss	    dec	    hex	filename
    435	      0	      0	    435	    1b3	atomic64_32.o.before
    435	      0	      0	    435	    1b3	atomic64_32.o.after

md5:
   bd8ab95e69c93518578bfaf0ea3be4d9  atomic64_32.o.before.asm
   bd8ab95e69c93518578bfaf0ea3be4d9  atomic64_32.o.after.asm

Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
LKML-Reference: <alpine.LFD.2.01.0907021653030.3210@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>


---
 arch/x86/lib/atomic64_32.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/lib/atomic64_32.c b/arch/x86/lib/atomic64_32.c
index a910238..fd28fd3 100644
--- a/arch/x86/lib/atomic64_32.c
+++ b/arch/x86/lib/atomic64_32.c
@@ -36,7 +36,7 @@ u64 atomic64_xchg(atomic64_t *ptr, u64 new_val)
 	u64 old_val;
 
 	do {
-		old_val = atomic_read(ptr);
+		old_val = __atomic64_read(ptr);
 	} while (atomic64_cmpxchg(ptr, old_val, new_val) != old_val);
 
 	return old_val;
--
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