cpu/hotplug: Use stop_machine_cpuslocked() in takedown_cpu()

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 <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170524081548.423292433@linutronix.de

diff --git a/kernel/cpu.c b/kernel/cpu.c
index e4389ac..142d889 100644 (file)
--- 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();