Re: Deadlock on poweroff

On Sun, Oct 07, 2012 at 09:03:11AM -0700, Paul E. McKenney wrote:

On Sun, Oct 07, 2012 at 05:47:11AM +0300, Kirill A. Shutemov wrote:

quoted

Hi Paul and all,

With commit 755609a9087fa983f567dc5452b2fa7b089b591f I've got deadlock on
poweroff.

It guess it happens because of race for cpu_hotplug.lock:

	CPU A					CPU B
disable_nonboot_cpus()
_cpu_down()
cpu_hotplug_begin()
 mutex_lock(&cpu_hotplug.lock);
__cpu_notify()
padata_cpu_callback()
__padata_remove_cpu()
padata_replace()
synchronize_rcu()
					rcu_gp_kthread()
					get_online_cpus();
					mutex_lock(&cpu_hotplug.lock);

Have you seen the issue before?

This is a new one for me.  Does the following (very lightly tested)
patch help?

Works for me. Thanks.

-- 
 Kirill A. Shutemov