Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756212Ab3CFJsU (ORCPT ); Wed, 6 Mar 2013 04:48:20 -0500 Received: from www.linutronix.de ([62.245.132.108]:41942 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752736Ab3CFJsS (ORCPT ); Wed, 6 Mar 2013 04:48:18 -0500 Date: Wed, 6 Mar 2013 10:48:08 +0100 (CET) From: Thomas Gleixner To: Daniel Lezcano cc: john.stultz@linaro.org, viresh.kumar@linaro.org, jacob.jun.pan@linux.intel.com, linux-arm-kernel@lists.infradead.org, santosh.shilimkar@ti.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linaro-kernel@lists.linaro.org, patches@linaro.org, rickard.andersson@stericsson.com, vincent.guittot@linaro.org, linus.walleij@stericsson.com Subject: Re: [PATCH 2/4][V2] time : set broadcast irq affinity In-Reply-To: <51370C09.5020301@linaro.org> Message-ID: References: <1362219013-18173-1-git-send-email-daniel.lezcano@linaro.org> <1362219013-18173-3-git-send-email-daniel.lezcano@linaro.org> <51370C09.5020301@linaro.org> User-Agent: Alpine 2.02 (LFD 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3462 Lines: 90 On Wed, 6 Mar 2013, Daniel Lezcano wrote: > On 03/05/2013 09:40 PM, Thomas Gleixner wrote: > > On Sat, 2 Mar 2013, Daniel Lezcano wrote: > >> When a cpu goes to a deep idle state where its local timer is shutdown, > >> it notifies the time frame work to use the broadcast timer instead. > >> > >> Unfortunately, the broadcast device could wake up any CPU, including an > >> idle one which is not concerned by the wake up at all. > >> > >> This implies, in the worst case, an idle CPU will wake up to send an IPI > >> to another idle cpu. > >> > >> This patch solves this by setting the irq affinity to the cpu concerned > >> by the nearest timer event, by this way, the CPU which is wake up is > >> guarantee to be the one concerned by the next event and we are safe with > >> unnecessary wakeup for another idle CPU. > >> > >> As the irq affinity is not supported by all the archs, a flag is needed > >> to specify which clocksource can handle it : CLOCK_EVT_FEAT_DYNIRQ > >> > >> Signed-off-by: Daniel Lezcano > >> --- > >> include/linux/clockchips.h | 5 +++++ > >> kernel/time/tick-broadcast.c | 40 +++++++++++++++++++++++++++++++++------- > >> 2 files changed, 38 insertions(+), 7 deletions(-) > >> > >> diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h > >> index 6634652..c93e2a6 100644 > >> --- a/include/linux/clockchips.h > >> +++ b/include/linux/clockchips.h > >> @@ -55,6 +55,11 @@ enum clock_event_nofitiers { > >> #define CLOCK_EVT_FEAT_C3STOP 0x000008 > >> #define CLOCK_EVT_FEAT_DUMMY 0x000010 > >> > >> +/* > >> + * Clock event device can set its irq affinity dynamically > >> + */ > >> +#define CLOCK_EVT_FEAT_DYNIRQ 0x000020 > >> + > >> /** > >> * struct clock_event_device - clock event device descriptor > >> * @event_handler: Assigned by the framework to be called by the low > >> diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c > >> index 6197ac0..9ca8ff5 100644 > >> --- a/kernel/time/tick-broadcast.c > >> +++ b/kernel/time/tick-broadcast.c > >> @@ -406,13 +406,37 @@ struct cpumask *tick_get_broadcast_oneshot_mask(void) > >> return to_cpumask(tick_broadcast_oneshot_mask); > >> } > >> > >> -static int tick_broadcast_set_event(struct clock_event_device *bc, > >> +/* > >> + * Set broadcast interrupt affinity > >> + */ > >> +static void tick_broadcast_set_affinity(struct clock_event_device *bc, > >> + const struct cpumask *cpumask) > >> +{ > >> + if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ)) > >> + return; > >> + > >> + if (cpumask_equal(bc->cpumask, cpumask)) > >> + return; > >> + > >> + bc->cpumask = cpumask; > > > > This breaks with CONFIG_CPUMASK_OFFSTACK=y. cpumask_copy() is your friend! > > This instruction copies the pointer, not the cpumask content. > > bc->cpumask is defined as a const struct cpumask * and is used to copy a > cpumask pointer not the content. > > The cpumask parameter is a pointer to a global cpumask provided by the > cpumask_of macro. > > But to be in the safe side, I compiled tested with > CONFIG_CPUMASK_OFFSTACK=y without problem. > > Did I missed something ? No, I misinterpreted the patch. Assigning a pointer is safe. Thanks, tglx -- 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/