Date: Tue, 7 Jul 2015 16:16:35 +0200
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-kernel@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] timer: nohz: don't disable the timer if we don't have
 irqwork interrupt
Message-ID: <20150707141633.GB20498@lerouge>
References: <1435068463-10091-1-git-send-email-bigeasy@linutronix.de>
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On Tue, Jun 23, 2015 at 04:07:43PM +0200, Sebastian Andrzej Siewior wrote:
> The irq work interrupt is optional: If an architecture does not provide
> it then the callback will be run from update_process_times(). This does
> not work well for nohz_full_kick_work_func() as we learned in commit
> 76a33061b932 ("irq_work: Force raised irq work to run on irq work
> interrupt").
> 
> This patch is just a precaution to ensure that that an irq work
> interrupt is required and the timer callback is not enough.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

But we already check that in tick_nohz_init(). Or am I missing something
else?

Thanks.

> ---
>  kernel/time/tick-sched.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
> index c792429e98c6..d9481bebae22 100644
> --- a/kernel/time/tick-sched.c
> +++ b/kernel/time/tick-sched.c
> @@ -176,6 +176,11 @@ static bool can_stop_full_tick(void)
>  		return false;
>  	}
>  
> +	if (!arch_irq_work_has_interrupt()) {
> +		trace_tick_stop(0, "missing irq work interrupt\n");
> +		return false;
> +	}
> +
>  	/* sched_clock_tick() needs us? */
>  #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
>  	/*
> -- 
> 2.1.4
> 
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