From: Sebastian Andrzej Siewior <bige...@linutronix.de>

takedown_cpu() is a cpu hotplug function invoking stop_machine(). The cpu
hotplug machinery holds the hotplug lock for write.

stop_machine() invokes get_online_cpus() as well. This is correct, but
prevents the conversion of the hotplug locking to a percpu rwsem.

Use stop_machine_cpuslocked() to avoid the nested call.

Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Steven Rostedt <rost...@goodmis.org>

---
 kernel/cpu.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -701,7 +701,7 @@ static int takedown_cpu(unsigned int cpu
        /*
         * So now all preempt/rcu users must observe !cpu_active().
         */
-       err = stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
+       err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
        if (err) {
                /* CPU refused to die */
                irq_unlock_sparse();


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