From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Lezcano Subject: Re: [PATCH 2/4][V2] time : set broadcast irq affinity Date: Wed, 06 Mar 2013 13:35:05 +0100 Message-ID: <513737F9.2080805@linaro.org> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail-pb0-f44.google.com ([209.85.160.44]:49344 "EHLO mail-pb0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751452Ab3CFMfM (ORCPT ); Wed, 6 Mar 2013 07:35:12 -0500 Received: by mail-pb0-f44.google.com with SMTP id wz12so5948279pbc.31 for ; Wed, 06 Mar 2013 04:35:12 -0800 (PST) In-Reply-To: Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Thomas Gleixner 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 On 03/06/2013 10:48 AM, Thomas Gleixner wrote: > 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 shut= down, >>>> it notifies the time frame work to use the broadcast timer instead= =2E >>>> >>>> Unfortunately, the broadcast device could wake up any CPU, includi= ng 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 conc= erned >>>> 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 saf= e with >>>> unnecessary wakeup for another idle CPU. >>>> >>>> As the irq affinity is not supported by all the archs, a flag is n= eeded >>>> 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= =2Eh >>>> 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 >>>> =20 >>>> +/* >>>> + * 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-broad= cast.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_m= ask(void) >>>> return to_cpumask(tick_broadcast_oneshot_mask); >>>> } >>>> =20 >>>> -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 =3D cpumask; >>> >>> This breaks with CONFIG_CPUMASK_OFFSTACK=3Dy. cpumask_copy() is you= r friend! >> >> This instruction copies the pointer, not the cpumask content. >> >> bc->cpumask is defined as a const struct cpumask * and is used to co= py a >> cpumask pointer not the content. >> >> The cpumask parameter is a pointer to a global cpumask provided by t= he >> cpumask_of macro. >> >> But to be in the safe side, I compiled tested with >> CONFIG_CPUMASK_OFFSTACK=3Dy without problem. >> >> Did I missed something ? >=20 > No, I misinterpreted the patch. Assigning a pointer is safe.=20 Ok, thanks anyway for reviewing the patch. Do you think it is acceptable for upstreaming ? -- Daniel Linaro.org =E2=94=82 Open source software for= ARM SoCs =46ollow Linaro: Facebook | Twitter | Blog