linux-kernel - Re: WARN_ON_ONCE(in_nmi()) hit in irq_work_queue

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Date:	Thu, 7 Aug 2014 10:13:21 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: WARN_ON_ONCE(in_nmi()) hit in irq_work_queue_on

On Thu, Aug 07, 2014 at 01:44:58AM +0200, Frederic Weisbecker wrote:
> In fact the problem has arised since the recent irq work patches I did.

No, those just added the WARN, previously we send the resched IPI, and
that's equally wrong from NMI context.

> There I've changed tick_nohz_full_kick() to use irq_work_queue_on() instead
> of irq_work_queue() so it has become NMI unsafe by accident.
> 
> So I'd rather suggest this instead of queuing two levels of irq_work:

> +void tick_nohz_full_kick(void)
> +{
> +	if (!tick_nohz_full_cpu(smp_processor_id()))
> +		irq_work_queue(&__get_cpu_var(nohz_full_kick_work));
> +}

Indeed, that's better. Thanks!

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