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Date: Sun, 7 Oct 2012 05:47:11 +0300
From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        linux-kernel@vger.kernel.org
Cc: Dipankar Sarma <dipankar@in.ibm.com>, Thomas Gleixner <tglx@linutronix.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Steffen Klassert <steffen.klassert@secunet.com>,
        ".linux-crypto"@vger.kernel.org
Subject: Deadlock on poweroff
Message-ID: <20121007024711.GA21403@shutemov.name>
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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