diff options
| author | Andrea Parri <parri.andrea@gmail.com> | 2018-02-27 05:00:58 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2018-03-12 10:59:03 +0100 |
| commit | fbfcd0199170984bd3c2812e49ed0fe7b226959a (patch) | |
| tree | a17482251a965cb047cda3d91bbc4810aeb3a48b /arch/alpha/include/asm/cmpxchg.h | |
| parent | bd5c0ba2cd78a4c116726ead84f8f37dc92d043e (diff) | |
locking/xchg/alpha: Remove superfluous memory barriers from the _local() variants
The following two commits:
79d442461df74 ("locking/xchg/alpha: Clean up barrier usage by using smp_mb() in place of __ASM__MB")
472e8c55cf662 ("locking/xchg/alpha: Fix xchg() and cmpxchg() memory ordering bugs")
... ended up adding unnecessary barriers to the _local() variants on Alpha,
which the previous code took care to avoid.
Fix them by adding the smp_mb() into the cmpxchg() macro rather than into the
____cmpxchg() variants.
Reported-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrea Parri <parri.andrea@gmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-alpha@vger.kernel.org
Fixes: 472e8c55cf662 ("locking/xchg/alpha: Fix xchg() and cmpxchg() memory ordering bugs")
Fixes: 79d442461df74 ("locking/xchg/alpha: Clean up barrier usage by using smp_mb() in place of __ASM__MB")
Link: http://lkml.kernel.org/r/1519704058-13430-1-git-send-email-parri.andrea@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/alpha/include/asm/cmpxchg.h')
| -rw-r--r-- | arch/alpha/include/asm/cmpxchg.h | 20 |
1 files changed, 16 insertions, 4 deletions
diff --git a/arch/alpha/include/asm/cmpxchg.h b/arch/alpha/include/asm/cmpxchg.h index 8a2b331e43fe..6c7c39452471 100644 --- a/arch/alpha/include/asm/cmpxchg.h +++ b/arch/alpha/include/asm/cmpxchg.h @@ -38,19 +38,31 @@ #define ____cmpxchg(type, args...) __cmpxchg ##type(args) #include <asm/xchg.h> +/* + * The leading and the trailing memory barriers guarantee that these + * operations are fully ordered. + */ #define xchg(ptr, x) \ ({ \ + __typeof__(*(ptr)) __ret; \ __typeof__(*(ptr)) _x_ = (x); \ - (__typeof__(*(ptr))) __xchg((ptr), (unsigned long)_x_, \ - sizeof(*(ptr))); \ + smp_mb(); \ + __ret = (__typeof__(*(ptr))) \ + __xchg((ptr), (unsigned long)_x_, sizeof(*(ptr))); \ + smp_mb(); \ + __ret; \ }) #define cmpxchg(ptr, o, n) \ ({ \ + __typeof__(*(ptr)) __ret; \ __typeof__(*(ptr)) _o_ = (o); \ __typeof__(*(ptr)) _n_ = (n); \ - (__typeof__(*(ptr))) __cmpxchg((ptr), (unsigned long)_o_, \ - (unsigned long)_n_, sizeof(*(ptr)));\ + smp_mb(); \ + __ret = (__typeof__(*(ptr))) __cmpxchg((ptr), \ + (unsigned long)_o_, (unsigned long)_n_, sizeof(*(ptr)));\ + smp_mb(); \ + __ret; \ }) #define cmpxchg64(ptr, o, n) \ |