[patch V2 14/24] cpu/hotplug: Use stop_machine_cpuslocked() in takedown_cpu()

Thomas Gleixner
2017-04-18T19:50:51Z

[-- Attachment #1: cpu-hotplug-Use-stop-machine-locked.patch --]
[-- Type: text/plain, Size: 941 bytes --]

From: Sebastian Andrzej Siewior <bigeasy@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 <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
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();