[PATCH] use smp_mb/wmb/rmb where possible

Replace a number of memory barriers with smp_ variants.  This means we won't
take the unnecessary hit on UP machines.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 5 deletions

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index c39ed70af174..6116b25aa7cf 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -33,7 +33,7 @@ static int stopmachine(void *cpu)
         set_cpus_allowed(current, cpumask_of_cpu((int)(long)cpu));
 
         /* Ack: we are alive */
-        mb(); /* Theoretically the ack = 0 might not be on this CPU yet. */
+        smp_mb(); /* Theoretically the ack = 0 might not be on this CPU yet. */
         atomic_inc(&stopmachine_thread_ack);
 
         /* Simple state machine */
@@ -43,14 +43,14 @@ static int stopmachine(void *cpu)
                         local_irq_disable();
                         irqs_disabled = 1;
                         /* Ack: irqs disabled. */
-                        mb(); /* Must read state first. */
+                        smp_mb(); /* Must read state first. */
                         atomic_inc(&stopmachine_thread_ack);
                 } else if (stopmachine_state == STOPMACHINE_PREPARE
                            && !prepared) {
                         /* Everyone is in place, hold CPU. */
                         preempt_disable();
                         prepared = 1;
-                        mb(); /* Must read state first. */
+                        smp_mb(); /* Must read state first. */
                         atomic_inc(&stopmachine_thread_ack);
                 }
                 /* Yield in first stage: migration threads need to
@@ -62,7 +62,7 @@ static int stopmachine(void *cpu)
         }
 
         /* Ack: we are exiting. */
-        mb(); /* Must read state first. */
+        smp_mb(); /* Must read state first. */
         atomic_inc(&stopmachine_thread_ack);
 
         if (irqs_disabled)
@@ -77,7 +77,7 @@ static int stopmachine(void *cpu)
 static void stopmachine_set_state(enum stopmachine_state state)
 {
         atomic_set(&stopmachine_thread_ack, 0);
-        wmb();
+        smp_wmb();
         stopmachine_state = state;
         while (atomic_read(&stopmachine_thread_ack) != stopmachine_num_threads)
                 cpu_relax();