linux-kernel - Re: [patch 15/16] cpufreq: intel-pstate: Use del_timer_sync in intel_pstate_cpu

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Date:	Mon, 24 Mar 2014 10:15:02 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Julia Lawall <Julia.Lawall@...6.fr>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	cpufreq <cpufreq@...r.kernel.org>, pm <linux-pm@...r.kernel.org>
Subject: Re: [patch 15/16] cpufreq: intel-pstate: Use del_timer_sync in intel_pstate_cpu_exit()

On Sun, Mar 23, 2014 at 8:39 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> We are about to free the data structure. Make sure no timer callback
> is running. I might be paranoid, but the ->exit callback can be
> invoked from so many places, that it is not entirely clear whether
> del_timer is always called on the cpu on which it is enqueued.

In normal cases it will be called only when CPU goes offline and I
hope that isn't called on the dying CPU.

> While looking through the call sites I noticed, that
> cpufreq_init_policy() can fail and invoke cpufreq_driver->exit() but
> it does not return the failure and the callsite happily proceeds.

Thanks for reporting this, will get it fixed.

> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: cpufreq <cpufreq@...r.kernel.org>
> Cc: pm <linux-pm@...r.kernel.org>
> ---
>
>  drivers/cpufreq/intel_pstate.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: tip/drivers/cpufreq/intel_pstate.c
> ===================================================================
> --- tip.orig/drivers/cpufreq/intel_pstate.c
> +++ tip/drivers/cpufreq/intel_pstate.c
> @@ -777,7 +777,7 @@ static int intel_pstate_cpu_exit(struct
>  {
>         int cpu = policy->cpu;
>
> -       del_timer(&all_cpu_data[cpu]->timer);
> +       del_timer_sync(&all_cpu_data[cpu]->timer);

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
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