linux-kernel - Re: [PATCH 1/2] timer: avoid unnecessary waking up of nohz CPU

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 29 Apr 2015 08:11:58 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Joonwoo Park <joonwoop@...eaurora.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Saravana Kannan <skannan@...eaurora.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	John Stultz <john.stultz@...aro.org>
Subject: Re: [PATCH 1/2] timer: avoid unnecessary waking up of nohz CPU

On Tue, Apr 28, 2015 at 7:51 AM, Joonwoo Park <joonwoop@...eaurora.org> wrote:
> At present, internal_add_timer() examines flags with 'base' which doesn't
> contain flags.  Examine with 'timer->base' to avoid unnecessary waking up
> of nohz CPU when timer base has TIMER_DEFERRABLE.
>
> CC: Thomas Gleixner <tglx@...utronix.de>
> CC: John Stultz <john.stultz@...aro.org>
> Signed-off-by: Joonwoo Park <joonwoop@...eaurora.org>
> ---
>  kernel/time/timer.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/time/timer.c b/kernel/time/timer.c
> index 2ece3aa..e5d5733c 100644
> --- a/kernel/time/timer.c
> +++ b/kernel/time/timer.c
> @@ -434,7 +434,7 @@ static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
>          * require special care against races with idle_cpu(), lets deal
>          * with that later.
>          */
> -       if (!tbase_get_deferrable(base) || tick_nohz_full_cpu(base->cpu))
> +       if (!tbase_get_deferrable(timer->base) || tick_nohz_full_cpu(base->cpu))
>                 wake_up_nohz_cpu(base->cpu);
>  }

Oops !!

Fixes: 9f6d9baaa8ca ("timer: Kick dynticks targets on mod_timer*() calls")
Cc: 3.17+ <stable@...r.kernel.org> # 3.17+

Reviewed-by: Viresh Kumar <viresh.kumar@...aro.org>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/