Re: Deadlock on poweroff

On 10/07/2012 10:20 PM, Kirill A. Shutemov wrote:

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

quoted

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.

Could you share the patch please? Looks like it didn't hit the mailing
lists.. 

Regards,
Srivatsa S. Bhat