Commit 705ac1ca authored by Pranith Kumar's avatar Pranith Kumar Committed by Paolo Bonzini
Browse files

atomics: Remove redundant barrier()'s 

Remove the redundant barrier() after the fence as agreed in previous
discussion here:
https://lists.gnu.org/archive/html/qemu-devel/2016-04/msg00489.html



Signed-off-by: default avatarPranith Kumar <bobby.prani@gmail.com>
Message-Id: <20160824204424.14041-3-bobby.prani@gmail.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent c2cd627d

include/qemu/atomic.h

+4 −4
Original line number Diff line number Diff line
@@ -72,16 +72,16 @@ 
 * Add one here, and similarly in smp_rmb() and smp_read_barrier_depends().

 */



#define smp_mb()    ({ barrier(); __atomic_thread_fence(__ATOMIC_SEQ_CST); barrier(); })

#define smp_wmb()   ({ barrier(); __atomic_thread_fence(__ATOMIC_RELEASE); barrier(); })

#define smp_rmb()   ({ barrier(); __atomic_thread_fence(__ATOMIC_ACQUIRE); barrier(); })

#define smp_mb()    ({ barrier(); __atomic_thread_fence(__ATOMIC_SEQ_CST); })

#define smp_wmb()   ({ barrier(); __atomic_thread_fence(__ATOMIC_RELEASE); })

#define smp_rmb()   ({ barrier(); __atomic_thread_fence(__ATOMIC_ACQUIRE); })



/* Most compilers currently treat consume and acquire the same, but really

 * no processors except Alpha need a barrier here.  Leave it in if

 * using Thread Sanitizer to avoid warnings, otherwise optimize it away.

 */

#if defined(__SANITIZE_THREAD__)

#define smp_read_barrier_depends() ({ barrier(); __atomic_thread_fence(__ATOMIC_CONSUME); barrier(); })

#define smp_read_barrier_depends() ({ barrier(); __atomic_thread_fence(__ATOMIC_CONSUME); })

#elsif defined(__alpha__)

#define smp_read_barrier_depends()   asm volatile("mb":::"memory")

#else