linux-kernel - Re: Deadlock on poweroff

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Message-ID: <20121008044128.GA31861@linux.vnet.ibm.com>
Date:	Sun, 7 Oct 2012 21:41:28 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	linux-kernel@...r.kernel.org, Dipankar Sarma <dipankar@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Steffen Klassert <steffen.klassert@...unet.com>,
	linux-crypto@...r.kernel.org
Subject: Re: Deadlock on poweroff

On Sun, Oct 07, 2012 at 07:50:12PM +0300, Kirill A. Shutemov wrote:
> 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:
> > > 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.

May I add your Tested-by?

							Thanx, Paul

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