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 <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
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Cc: [email protected]
Cc: [email protected]
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Link: https://lkml.kernel.org/r/[email protected]

diff --git a/kernel/cpu.c b/kernel/cpu.c
index aa7fe85ad62e86de2060d2b89e525b93506cbf0d..eb4041f78073d81e040a67aa734c897af5e1aa8a 100644 (file)
--- 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) {