4.18-stable review patch. If anyone has any objections, please let me know.
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From: Neeraj Upadhyay neeraju@codeaurora.org
commit f8b7530aa0a1def79c93101216b5b17cf408a70a upstream.
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@codeauro... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/cpu.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -608,15 +608,15 @@ static void cpuhp_thread_fun(unsigned in 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) {