cpu/hotplug: Adjust misplaced smb() in cpuhp_thread_fun()

The smp_mb() in cpuhp_thread_fun() is misplaced. It needs to be after the
load of st->should_run to prevent reordering of the later load/stores
w.r.t. the load of st->should_run.

Fixes: 4dddfb5faa61 ("smp/hotplug: Rewrite AP state machine core")
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infraded.org>
Cc: josh@joshtriplett.org
Cc: peterz@infradead.org
Cc: jiangshanlai@gmail.com
Cc: dzickus@redhat.com
Cc: brendan.jackman@arm.com
Cc: malat@debian.org
Cc: mojha@codeaurora.org
Cc: sramana@codeaurora.org
Cc: linux-arm-msm@vger.kernel.org
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1536126727-11629-1-git-send-email-neeraju@codeaurora.org

1 files changed, 3 insertions, 3 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index aa7fe85ad62e..eb4041f78073 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -607,15 +607,15 @@ static void cpuhp_thread_fun(unsigned int cpu)
         bool bringup = st->bringup;
         enum cpuhp_state state;
 
+        if (WARN_ON_ONCE(!st->should_run))
+                return;
+
         /*
          * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
          * that if we see ->should_run we also see the rest of the state.
          */
         smp_mb();
 
-        if (WARN_ON_ONCE(!st->should_run))
-                return;
-
         cpuhp_lock_acquire(bringup);
 
         if (st->single) {