[PATCH] stop_machine: Avoid potential race behaviour of multi_stop_data::state

[Rong Tao]

From: Rong Tao <rongtao@xxxxxxxx>

In commit b1fc58333575 ("stop_machine: Avoid potential race behaviour")
fix both multi_cpu_stop() and set_state() access multi_stop_data::state,
We should ensure that multi_stop_data::state is accessed using the rwonce
method.

Signed-off-by: Rong Tao <rongtao@xxxxxxxx>
---
 kernel/stop_machine.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index cedb17ba158a..73de9ab77132 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -191,7 +191,7 @@ static void set_state(struct multi_stop_data *msdata,
 static void ack_state(struct multi_stop_data *msdata)
 {
 	if (atomic_dec_and_test(&msdata->thread_ack))
-		set_state(msdata, msdata->state + 1);
+		set_state(msdata, READ_ONCE(msdata->state) + 1);
 }
 
 notrace void __weak stop_machine_yield(const struct cpumask *cpumask)
-- 
2.42.0