From: Stephen Boyd <sboyd-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> To: Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org> Cc: Mark Rutland <Mark.Rutland-5wv7dgnIgG8@public.gmane.org>, Marc Zyngier <marc.zyngier-5wv7dgnIgG8@public.gmane.org>, "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, ARM kernel mailing list <linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>, John Stultz <john.stultz-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, Joseph Lo <josephl-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>, Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org> Subject: Re: CPU hotplug issue w/ 0647065 clocksource: Add generic dummy timer driver Date: Thu, 11 Jul 2013 07:00:59 -0700 [thread overview] Message-ID: <20130711140059.GA27430@codeaurora.org> (raw) In-Reply-To: <51DD872D.7020101-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org> On 07/10, Stephen Warren wrote: > On 07/09/2013 05:05 PM, Stephen Boyd wrote: > > On 07/09, Stephen Warren wrote: > >> On 07/09/2013 10:35 AM, Stephen Boyd wrote: > >>> On 07/09, Stephen Warren wrote: > >>>> On 07/08/2013 06:58 PM, Stephen Boyd wrote: > >>>>> On 07/08, Stephen Warren wrote: > >>>>>> CPU hotplug (replug) on Tegra HW seems to be occasionally broken due to > >>>>>> commit 0647065 "clocksource: Add generic dummy timer driver" in > >>>>>> linux-next. Reverting that commit solves the issue. > ... > > Can you try this patch? > > That seems to work great, thanks! I successfully unpugged/replugged CPU1 > about 200 times, whereas without the patch I'd usually see the problem > about 10% of replug attempts. > > Tested-by: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> > Thomas, here's the full patch: ---8<---- Subject: [PATCH] tick: Fix hotplug confusing the broadcast mode On ARM systems the dummy clockevent is registered with the cpu hotplug notifier chain before any other per-cpu clockevent. This has the side-effect of causing the dummy clockevent to be registered first in every hotplug sequence. Because the dummy is first, we'll try to turn the broadcast source on but the code in tick_device_uses_broadcast() assumes the broadcast source is in periodic mode and calls tick_broadcast_start_periodic() unconditionally. On boot this isn't a problem because we typically haven't switched into oneshot mode yet (if at all). During hotplug, if the broadcast source isn't in periodic mode we'll replace the broadcast oneshot handler with the broadcast periodic handler and start emulating oneshot mode when we shouldn't. Due to the way the broadcast oneshot handler programs the next_event it's possible for it to contain KTIME_MAX and cause us to hang the system when the periodic handler tries to program the next tick. Fix this by using the appropriate function to start the broadcast source. Reported-by: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> Tested-by: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> Signed-off-by: Stephen Boyd <sboyd-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> --- kernel/time/tick-broadcast.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index 6d3f916..218bcb5 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -157,7 +157,10 @@ int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu) dev->event_handler = tick_handle_periodic; tick_device_setup_broadcast_func(dev); cpumask_set_cpu(cpu, tick_broadcast_mask); - tick_broadcast_start_periodic(bc); + if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) + tick_broadcast_start_periodic(bc); + else + tick_broadcast_setup_oneshot(bc); ret = 1; } else { /* -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
WARNING: multiple messages have this Message-ID (diff)
From: sboyd@codeaurora.org (Stephen Boyd) To: linux-arm-kernel@lists.infradead.org Subject: CPU hotplug issue w/ 0647065 clocksource: Add generic dummy timer driver Date: Thu, 11 Jul 2013 07:00:59 -0700 [thread overview] Message-ID: <20130711140059.GA27430@codeaurora.org> (raw) In-Reply-To: <51DD872D.7020101@wwwdotorg.org> On 07/10, Stephen Warren wrote: > On 07/09/2013 05:05 PM, Stephen Boyd wrote: > > On 07/09, Stephen Warren wrote: > >> On 07/09/2013 10:35 AM, Stephen Boyd wrote: > >>> On 07/09, Stephen Warren wrote: > >>>> On 07/08/2013 06:58 PM, Stephen Boyd wrote: > >>>>> On 07/08, Stephen Warren wrote: > >>>>>> CPU hotplug (replug) on Tegra HW seems to be occasionally broken due to > >>>>>> commit 0647065 "clocksource: Add generic dummy timer driver" in > >>>>>> linux-next. Reverting that commit solves the issue. > ... > > Can you try this patch? > > That seems to work great, thanks! I successfully unpugged/replugged CPU1 > about 200 times, whereas without the patch I'd usually see the problem > about 10% of replug attempts. > > Tested-by: Stephen Warren <swarren@nvidia.com> > Thomas, here's the full patch: ---8<---- Subject: [PATCH] tick: Fix hotplug confusing the broadcast mode On ARM systems the dummy clockevent is registered with the cpu hotplug notifier chain before any other per-cpu clockevent. This has the side-effect of causing the dummy clockevent to be registered first in every hotplug sequence. Because the dummy is first, we'll try to turn the broadcast source on but the code in tick_device_uses_broadcast() assumes the broadcast source is in periodic mode and calls tick_broadcast_start_periodic() unconditionally. On boot this isn't a problem because we typically haven't switched into oneshot mode yet (if at all). During hotplug, if the broadcast source isn't in periodic mode we'll replace the broadcast oneshot handler with the broadcast periodic handler and start emulating oneshot mode when we shouldn't. Due to the way the broadcast oneshot handler programs the next_event it's possible for it to contain KTIME_MAX and cause us to hang the system when the periodic handler tries to program the next tick. Fix this by using the appropriate function to start the broadcast source. Reported-by: Stephen Warren <swarren@nvidia.com> Tested-by: Stephen Warren <swarren@nvidia.com> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> --- kernel/time/tick-broadcast.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index 6d3f916..218bcb5 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -157,7 +157,10 @@ int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu) dev->event_handler = tick_handle_periodic; tick_device_setup_broadcast_func(dev); cpumask_set_cpu(cpu, tick_broadcast_mask); - tick_broadcast_start_periodic(bc); + if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) + tick_broadcast_start_periodic(bc); + else + tick_broadcast_setup_oneshot(bc); ret = 1; } else { /* -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
next prev parent reply other threads:[~2013-07-11 14:00 UTC|newest] Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-07-08 17:36 CPU hotplug issue w/ 0647065 clocksource: Add generic dummy timer driver Stephen Warren 2013-07-08 17:36 ` Stephen Warren [not found] ` <51DAF895.1020700-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org> 2013-07-09 0:58 ` Stephen Boyd 2013-07-09 0:58 ` Stephen Boyd [not found] ` <20130709005837.GC830-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> 2013-07-09 16:05 ` Stephen Warren 2013-07-09 16:05 ` Stephen Warren [not found] ` <51DC34AD.30009-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org> 2013-07-09 16:35 ` Stephen Boyd 2013-07-09 16:35 ` Stephen Boyd [not found] ` <20130709163518.GD830-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> 2013-07-09 16:52 ` Stephen Warren 2013-07-09 16:52 ` Stephen Warren [not found] ` <51DC3FD2.9070308-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org> 2013-07-09 23:05 ` Stephen Boyd 2013-07-09 23:05 ` Stephen Boyd [not found] ` <20130709230528.GE830-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> 2013-07-10 16:09 ` Stephen Warren 2013-07-10 16:09 ` Stephen Warren [not found] ` <51DD872D.7020101-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org> 2013-07-11 14:00 ` Stephen Boyd [this message] 2013-07-11 14:00 ` Stephen Boyd 2013-07-12 10:39 ` [tip:timers/urgent] tick: broadcast: Check broadcast mode on CPU hotplug tip-bot for Stephen Boyd
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20130711140059.GA27430@codeaurora.org \ --to=sboyd-sgv2jx0feol9jmxxk+q4oq@public.gmane.org \ --cc=Mark.Rutland-5wv7dgnIgG8@public.gmane.org \ --cc=john.stultz-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org \ --cc=josephl-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org \ --cc=linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org \ --cc=linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \ --cc=marc.zyngier-5wv7dgnIgG8@public.gmane.org \ --cc=swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org \ --cc=tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.