From 3217120873598533234b6dedda9c371ce30001d0 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Fri, 3 Jul 2009 13:06:01 +0200
Subject: [PATCH] x86: atomic64: Make atomic_read() type-safe
MIME-Version: 1.0
Content-Type: text/plain; charset=utf8
Content-Transfer-Encoding: 8bit

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.

Change atomic_read() to be a type-safe inline, and this exposes
the atomic64 bogosity as well:

  arch/x86/lib/atomic64_32.c: In function ‘atomic64_xchg’:
  arch/x86/lib/atomic64_32.c:39: warning: passing argument 1 of ‘atomic_read’ from incompatible pointer type

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
LKML-Reference: <alpine.LFD.2.01.0907021653030.3210@localhost.localdomain>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/include/asm/atomic_32.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/atomic_32.h b/arch/x86/include/asm/atomic_32.h
index 311a43e..b551bb1 100644
--- a/arch/x86/include/asm/atomic_32.h
+++ b/arch/x86/include/asm/atomic_32.h
@@ -19,7 +19,10 @@
  *
  * Atomically reads the value of @v.
  */
-#define atomic_read(v)		((v)->counter)
+static inline int atomic_read(const atomic_t *v)
+{
+	return v->counter;
+}
 
 /**
  * atomic_set - set atomic variable
-- 
2.7.4