From: Arnd Bergmann <arnd@arndb.de>
To: Jonas Bonn <jonas@southpole.se>
Subject: Re: [PATCH 11/19] OpenRISC: Idle/Power management
Date: Mon, 20 Jun 2011 10:20:39 +0200
User-Agent: KMail/1.13.6 (Linux/3.0.0-rc1nosema+; KDE/4.6.3; x86_64; ; )
Cc: linux-kernel@vger.kernel.org
References: <1308483825-6023-1-git-send-email-jonas@southpole.se> <1308483825-6023-12-git-send-email-jonas@southpole.se>
In-Reply-To: <1308483825-6023-12-git-send-email-jonas@southpole.se>
MIME-Version: 1.0
Content-Type: Text/Plain;
  charset="iso-8859-15"
Content-Transfer-Encoding: 7bit
Message-Id: <201106201020.39097.arnd@arndb.de>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1748
Lines: 47

On Sunday 19 June 2011 13:43:37 Jonas Bonn wrote:
> +void cpu_idle(void)
> +{
> +        unsigned int cpu = smp_processor_id();
> +
> +        set_thread_flag(TIF_POLLING_NRFLAG);
> +
> +        /* endless idle loop with no priority at all */
> +        while (1) {
> +                tick_nohz_stop_sched_tick(1);
> +
> +                while (!need_resched()) {
> +                        check_pgt_cache();
> +                        rmb();
> +
> +/*                        if (cpu_is_offline(cpu))
> +                                play_dead();
> +*/
> +                       clear_thread_flag(TIF_POLLING_NRFLAG);
> +
> +                        local_irq_disable();
> +                        /* Don't trace irqs off for idle */
> +                        stop_critical_timings();
> +                       if (powersave != NULL )
> +                               powersave();
> +                       start_critical_timings();
> +                       local_irq_enable();
> +                       set_thread_flag(TIF_POLLING_NRFLAG);
> +                }
> +
> +                tick_nohz_restart_sched_tick();
> +                preempt_enable_no_resched();
> +                schedule();
> +                preempt_disable();
> +        }

Shouldn't you check need_resched() inside of local_irq_disable? Otherwise
you may get interrupted between the check at the start of the loop and
the irq_disable, which tries to wake up another process just before you go
to sleep indefinitely.

	Arnd
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/