linux-kernel - Deadlock on poweroff

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Date:	Sun, 7 Oct 2012 05:47:11 +0300
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Cc:	Dipankar Sarma <dipankar@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Steffen Klassert <steffen.klassert@...unet.com>,
	".linux-crypto"@vger.kernel.org
Subject: Deadlock on poweroff

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?

-- 
 Kirill A. Shutemov
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