linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Sudeep Holla <sudeep.holla@arm.com>,
	Peter Zijlstra <peterz@infradead.org>
Cc: Linus Walleij <linus.walleij@linaro.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Linux PM list <linux-pm@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	ACPI Devel Maling List <linux-acpi@vger.kernel.org>
Subject: Re: [PATCH 16/20] sched/idle: Use explicit broadcast oneshot control function
Date: Wed, 29 Apr 2015 11:44:30 +0200	[thread overview]
Message-ID: <5540A7FE.4030301@linaro.org> (raw)
In-Reply-To: <6185796.9I7OmaAAcQ@vostro.rjw.lan>

On 04/29/2015 03:04 AM, Rafael J. Wysocki wrote:
> On Wednesday, April 29, 2015 02:50:22 AM Rafael J. Wysocki wrote:
>> On Tuesday, April 28, 2015 02:58:37 PM Sudeep Holla wrote:
>>>
>>> On 28/04/15 15:14, Rafael J. Wysocki wrote:
>>>> On Tuesday, April 28, 2015 03:37:44 PM Rafael J. Wysocki wrote:
>>>>> On Tuesday, April 28, 2015 03:31:54 PM Rafael J. Wysocki wrote:
>>>>>> On Tuesday, April 28, 2015 02:37:10 PM Linus Walleij wrote:
>>>>>>> On Tue, Apr 28, 2015 at 2:19 PM, Rafael J. Wysocki <rafael@kernel.org> wrote:
>>>>>>>> Sudeep:
>>>>>>>>> At-least I observed issue only when I am using hardware broadcast timer.
>>>>>>>>> It doesn't hang when I am using hrtimer as broadcast timer in which case
>>>>>>>>> one of the cpu will be not enter deeper idle states that lose timer.
>>>>>>>>> I will rerun on v4.1-rc1 and post the complete log.
>>>>>>>>
>>>>>>>> So the bug here is that cpuidle_enter() enables interrupts, so the
>>>>>>>> assumption about them being not enabled made by
>>>>>>>> tick_broadcast_oneshot_control() is actually not valid.
>>>>>>>>
>>>>>>>> It looks like we need to acquire the clockevents_lock at least in this
>>>>>>>> particular case.  Let me see where to put it and I'll send a patch for
>>>>>>>> testing.
>>>>>>>
>>>>>>> Aha that looks very much like it. Put me on the patch and I'll
>>>>>>> take it for a spin.
>>>>>>
>>>>>> OK, so something like the below for starters (the _irqsave variant is used to
>>>>>> avoid adding one more WARN_ON(irqs_disabled()) in there).
>>>>>>
>>>>>> I haven't tested it, but then I can't reproduce the original issue in the
>>>>>> first place.
>>>>>
>>>>> Of course, the whole "broadcast" thing could be done from cpuidle_enter()
>>>>> in the first place, but then we could not avoid the problem with the cpuidle
>>>>> *callback* enabling interrupts possibly in there anyway (not to mention the
>>>>> "coupled" stuff).
>>>>
>>>> That said, if the given state is marked with CPUIDLE_FLAG_TIMER_STOP, I really
>>>> wouldn't expect it to re-enable interrupts on exit and the "coupled" thing
>>>> seems to be fundamentally at odds with that flag either.
>>>>
>>>> So it should be possible to move the "broadcast" logic into the cpuidle layer,
>>>> which I'm going to try to do.
>>>>
>>>
>>> Makes sense.
>>>
>>>> Please test the patch I've sent, though, as it should bring the code back to
>>>> where it was before the clockevents_notify() removal and it'd be good to verify
>>>> that.
>>>>
>>>
>>> I tested your patch and it works now. Anyways I am continuing to run
>>> stress tests on my board. I will report if I find any issues.
>>
>> Great, thanks!
>>
>> Below is the patch I came up with in the meantime.
>>
>> This moves the "switch to broadcast" timer logic into
>> cpuidle_enter_state() which allows tick_broadcast_exit() to be
>> called directly with interrupts disabled (as required), but
>> it also adds a fallback branch reflecting the 4.0 and earlier
>> behavior for idle states that enable interrupts on exit
>> from their ->enter callbacks.
>>
>> I'm not aware of any valid cases when CPUIDLE_FLAG_TIMER_STOP can be
>> set for such states, but people may try to add stuff like that in the
>> future, so it's better to catch that (hence the WARN_ON_ONCE) and do
>> our best to handle it gracefully anyway, IMO.
>>
>> The "if (entered_state == -EBUSY)" check is conservative.  It may
>> be better to do "if (entered_state < 0)" and fall back to the default
>> on all errors, but that's not what we do today (I guess the concern
>> would be "what if the state ->enter returns an error after entering
>> and exiting the idle state, in which case we may miss a wakeup event
>> if we fall back to the default").
>
> Actually, if my understanding of things is correct (the local clock event
> device cannot go away from under code executed with interrupts disabled
> on the local CPU), the simplified one below should be sufficient.

Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>

> ---
>   drivers/cpuidle/cpuidle.c |   16 ++++++++++++++++
>   kernel/sched/idle.c       |   16 ++--------------
>   2 files changed, 18 insertions(+), 14 deletions(-)
>
> Index: linux-pm/kernel/sched/idle.c
> ===================================================================
> --- linux-pm.orig/kernel/sched/idle.c
> +++ linux-pm/kernel/sched/idle.c
> @@ -81,7 +81,6 @@ static void cpuidle_idle_call(void)
>   	struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
>   	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
>   	int next_state, entered_state;
> -	unsigned int broadcast;
>   	bool reflect;
>
>   	/*
> @@ -150,17 +149,6 @@ static void cpuidle_idle_call(void)
>   		goto exit_idle;
>   	}
>
> -	broadcast = drv->states[next_state].flags & CPUIDLE_FLAG_TIMER_STOP;
> -
> -	/*
> -	 * Tell the time framework to switch to a broadcast timer
> -	 * because our local timer will be shutdown. If a local timer
> -	 * is used from another cpu as a broadcast timer, this call may
> -	 * fail if it is not available
> -	 */
> -	if (broadcast && tick_broadcast_enter())
> -		goto use_default;
> -
>   	/* Take note of the planned idle state. */
>   	idle_set_state(this_rq(), &drv->states[next_state]);
>
> @@ -174,8 +162,8 @@ static void cpuidle_idle_call(void)
>   	/* The cpu is no longer idle or about to enter idle. */
>   	idle_set_state(this_rq(), NULL);
>
> -	if (broadcast)
> -		tick_broadcast_exit();
> +	if (entered_state == -EBUSY)
> +		goto use_default;
>
>   	/*
>   	 * Give the governor an opportunity to reflect on the outcome
> Index: linux-pm/drivers/cpuidle/cpuidle.c
> ===================================================================
> --- linux-pm.orig/drivers/cpuidle/cpuidle.c
> +++ linux-pm/drivers/cpuidle/cpuidle.c
> @@ -158,9 +158,18 @@ int cpuidle_enter_state(struct cpuidle_d
>   	int entered_state;
>
>   	struct cpuidle_state *target_state = &drv->states[index];
> +	bool broadcast = !!(target_state->flags & CPUIDLE_FLAG_TIMER_STOP);
>   	ktime_t time_start, time_end;
>   	s64 diff;
>
> +	/*
> +	 * Tell the time framework to switch to a broadcast timer because our
> +	 * local timer will be shut down.  If a local timer is used from another
> +	 * CPU as a broadcast timer, this call may fail if it is not available.
> +	 */
> +	if (broadcast && tick_broadcast_enter())
> +		return -EBUSY;
> +
>   	trace_cpu_idle_rcuidle(index, dev->cpu);
>   	time_start = ktime_get();
>
> @@ -169,6 +178,13 @@ int cpuidle_enter_state(struct cpuidle_d
>   	time_end = ktime_get();
>   	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
>
> +	if (broadcast) {
> +		if (WARN_ON_ONCE(!irqs_disabled()))
> +			local_irq_disable();
> +
> +		tick_broadcast_exit();
> +	}
> +
>   	if (!cpuidle_state_is_coupled(dev, drv, entered_state))
>   		local_irq_enable();
>
>


-- 
  <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog


  parent reply	other threads:[~2015-04-29  9:44 UTC|newest]

Thread overview: 90+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-01 22:02 [PATCH 00/20] clockevents_notify() removal Rafael J. Wysocki
2015-04-01 22:03 ` [PATCH 01/20] clockevents: Provide explicit broadcast control functions Rafael J. Wysocki
2015-04-01 22:04 ` [PATCH 02/20] x86, amd_idle: Use explicit broadcast control function Rafael J. Wysocki
2015-04-01 22:05 ` [PATCH 03/20] ACPI / PAD: " Rafael J. Wysocki
2015-04-01 22:06 ` [PATCH 04/20] ACPI / processor: " Rafael J. Wysocki
2015-04-01 22:07 ` [PATCH 05/20] cpuidle: " Rafael J. Wysocki
2015-04-01 22:09 ` [PATCH 06/20] intel_idle: " Rafael J. Wysocki
2015-04-01 22:10 ` [PATCH 07/20] ARM: OMAP: " Rafael J. Wysocki
2015-04-01 22:11 ` [PATCH 08/20] clockevents: Remove the broadcast control leftovers Rafael J. Wysocki
2015-04-01 22:13 ` [PATCH 09/20] clockevents: Provide explicit broadcast oneshot control functions Rafael J. Wysocki
2015-04-01 22:15 ` [PATCH 10/20] x86, amd_idle: Use " Rafael J. Wysocki
2015-04-01 22:16 ` [PATCH 11/20] ACPI / PAD: Use explicit broadcast oneshot control function Rafael J. Wysocki
2015-04-01 22:17 ` [PATCH 12/20] ACPI / processor: Use explicit broadcast controll function Rafael J. Wysocki
2015-04-01 22:20 ` [PATCH 13/20] intel_idle: Use explicit broadcast oneshot control function Rafael J. Wysocki
2015-04-01 22:20 ` [PATCH 14/20] ARM: OMAP: " Rafael J. Wysocki
2015-04-01 22:21 ` [PATCH 15/20] ARM: tegra: " Rafael J. Wysocki
2015-04-01 22:22 ` [PATCH 16/20] sched/idle: " Rafael J. Wysocki
2015-04-28 10:11   ` Linus Walleij
2015-04-28 10:17     ` Sudeep Holla
2015-04-28 10:34     ` Daniel Lezcano
2015-04-28 10:42       ` Sudeep Holla
2015-04-28 12:19         ` Rafael J. Wysocki
2015-04-28 12:37           ` Linus Walleij
2015-04-28 13:31             ` Rafael J. Wysocki
2015-04-28 13:37               ` Rafael J. Wysocki
2015-04-28 14:14                 ` Rafael J. Wysocki
2015-04-28 13:58                   ` Sudeep Holla
2015-04-29  0:50                     ` Rafael J. Wysocki
2015-04-29  1:04                       ` Rafael J. Wysocki
2015-04-29  7:10                         ` Linus Walleij
2015-04-29  8:57                         ` Peter Zijlstra
2015-04-29  9:44                         ` Daniel Lezcano [this message]
2015-04-29  9:50                         ` Sudeep Holla
2015-04-29 14:07                           ` [PATCH][Fix] cpuidle: Run tick_broadcast_exit() with disabled interrupts Rafael J. Wysocki
2015-04-30  3:47                             ` Preeti U Murthy
2015-04-30 20:12                             ` Nicolas Pitre
2015-04-30 22:10                               ` Rafael J. Wysocki
2015-04-30  3:45                         ` [PATCH 16/20] sched/idle: Use explicit broadcast oneshot control function Preeti U Murthy
2015-04-28 13:04           ` Sudeep Holla
2015-04-01 22:23 ` [PATCH 17/20] clockevents: Remove broadcast oneshot control leftovers Rafael J. Wysocki
2015-04-01 22:24 ` [PATCH 18/20] clockevents: Make tick handover explicit Rafael J. Wysocki
2015-04-01 22:25 ` [PATCH 19/20] clockevents: Cleanup dead cpu explicitely Rafael J. Wysocki
2015-04-01 22:26 ` [PATCH 20/20] timekeeping: Get rid of stale comment Rafael J. Wysocki
2015-04-01 23:57   ` John Stultz
2015-04-02 12:39 ` [PATCH 00/20] clockevents_notify() removal Ingo Molnar
2015-04-02 22:19   ` Rafael J. Wysocki
2015-04-02 23:45     ` [v2][PATCH 00/21] " Rafael J. Wysocki
2015-04-02 23:46       ` [v2][PATCH 01/21] ACPI / PAD: Remove the local APIC nonsense Rafael J. Wysocki
2015-04-03  8:21         ` [tip:timers/core] ACPI/PAD: " tip-bot for Thomas Gleixner
2015-04-03  0:01       ` [v2][PATCH 02/21] clockevents: Provide explicit broadcast control functions Rafael J. Wysocki
2015-04-03  8:21         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:01       ` [v2][PATCH 03/21] x86, amd_idle: Use explicit broadcast control function Rafael J. Wysocki
2015-04-03  8:22         ` [tip:timers/core] x86/amd/idle, clockevents: " tip-bot for Thomas Gleixner
2015-04-03  0:01       ` [v2][PATCH 04/21] ACPI / PAD: " Rafael J. Wysocki
2015-04-03  8:22         ` [tip:timers/core] ACPI/PAD: " tip-bot for Thomas Gleixner
2015-04-03  0:02       ` [v2][PATCH 05/21] ACPI / processor: " Rafael J. Wysocki
2015-04-03  8:22         ` [tip:timers/core] ACPI/processor: " tip-bot for Thomas Gleixner
2015-04-03  0:02       ` [v2][PATCH 06/21] cpuidle: " Rafael J. Wysocki
2015-04-03  8:23         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:02       ` [v2][PATCH 07/21] intel_idle: " Rafael J. Wysocki
2015-04-03  8:23         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:02       ` [v2][PATCH 08/21] ARM: OMAP: " Rafael J. Wysocki
2015-04-03  8:23         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:03       ` [v2][PATCH 09/21] clockevents: Remove the broadcast control leftovers Rafael J. Wysocki
2015-04-03  8:23         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:05       ` [v2][PATCH 10/21] clockevents: Provide explicit broadcast oneshot control functions Rafael J. Wysocki
2015-04-03  8:24         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:05       ` [v2][PATCH 11/21] x86, amd_idle: Use " Rafael J. Wysocki
2015-04-03  8:24         ` [tip:timers/core] x86/amd/idle, clockevents: " tip-bot for Thomas Gleixner
2015-04-03  0:06       ` [v2][PATCH 12/21] ACPI / PAD: Use explicit broadcast oneshot control function Rafael J. Wysocki
2015-04-03  8:24         ` [tip:timers/core] ACPI/PAD: " tip-bot for Thomas Gleixner
2015-04-03  0:12       ` [v2][PATCH 13/21] ACPI / processor: Use explicit broadcast controll function Rafael J. Wysocki
2015-04-03  8:25         ` [tip:timers/core] ACPI/idle: Use explicit broadcast control function tip-bot for Thomas Gleixner
2015-04-03  0:14       ` [v2][PATCH 14/21] intel_idle: Use explicit broadcast oneshot " Rafael J. Wysocki
2015-04-03  8:25         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:31       ` [v2][PATCH 15/21] ARM: OMAP: " Rafael J. Wysocki
2015-04-03  8:25         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:32       ` [v2][PATCH 16/21] ARM: tegra: " Rafael J. Wysocki
2015-04-03  8:25         ` [tip:timers/core] ARM: Tegra: " tip-bot for Thomas Gleixner
2015-04-03  0:34       ` [v2][PATCH 17/21] sched/idle: " Rafael J. Wysocki
2015-04-03  8:26         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:36       ` [v2][PATCH 18/21] clockevents: Remove broadcast oneshot control leftovers Rafael J. Wysocki
2015-04-03  8:26         ` [tip:timers/core] " tip-bot for Rafael J. Wysocki
2015-04-03  0:37       ` [v2][PATCH 19/21] clockevents: Make tick handover explicit Rafael J. Wysocki
2015-04-03  8:26         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:38       ` [v2][PATCH 20/21] clockevents: Cleanup dead cpu explicitely Rafael J. Wysocki
2015-04-03  8:26         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  0:39       ` [v2][PATCH 21/21] timekeeping: Get rid of stale comment Rafael J. Wysocki
2015-04-03  8:27         ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-04-03  6:45       ` [v2][PATCH 00/21] clockevents_notify() removal Ingo Molnar

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=5540A7FE.4030301@linaro.org \
    --to=daniel.lezcano@linaro.org \
    --cc=linus.walleij@linaro.org \
    --cc=linux-acpi@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-pm@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=peterz@infradead.org \
    --cc=rafael@kernel.org \
    --cc=rjw@rjwysocki.net \
    --cc=sudeep.holla@arm.com \
    --cc=tglx@linutronix.de \
    --subject='Re: [PATCH 16/20] sched/idle: Use explicit broadcast oneshot control function' \
    /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: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).