linux-kernel - Re: BUG: tick device NULL pointer during system initialization and shutdown

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Date:	Mon, 24 Jun 2013 15:57:28 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Prarit Bhargava <prarit@...hat.com>
cc:	Linux Kernel <linux-kernel@...r.kernel.org>, athorlton@....com,
	CAI Qian <caiqian@...hat.com>
Subject: Re: BUG: tick device NULL pointer during system initialization and
 shutdown

On Tue, 18 Jun 2013, Prarit Bhargava wrote:

> Similar panics reported during bringup here:
> 
> http://lists.infradead.org/pipermail/linux-arm-kernel/2013-May/166205.html
> http://lkml.org/lkml/2013/5/8/342
> 
> I've seen this a few times on 3.10 based kernels.
> 
> [  175.842027] Disabling non-boot CPUs ...
> [  475.827017] BUG: unable to handle kernel NULL pointer dereference at
> 0000000000000048

That looks like a stale bit in tick_broadcast_force_mask.

Does the patch below fix it?

Thanks,

	tglx
---

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 20d6fba..e01ca90 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -183,6 +183,8 @@ static void tick_do_broadcast(struct cpumask *mask)
 	int cpu = smp_processor_id();
 	struct tick_device *td;
 
+	cpumask_and(mask, mask, cpu_online_mask);
+
 	/*
 	 * Check, if the current cpu is in the mask
 	 */
@@ -212,7 +214,6 @@ static void tick_do_periodic_broadcast(void)
 {
 	raw_spin_lock(&tick_broadcast_lock);
 
-	cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask);
 	tick_do_broadcast(tmpmask);
 
 	raw_spin_unlock(&tick_broadcast_lock);
--
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