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 <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: David Howells <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Arnd Bergmann <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/x86/lib/atomic64_32.c b/arch/x86/lib/atomic64_32.c
index a910238a7760..fd28fd3fb742 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;