linux-kernel - Re: [PATCH 16/20] sched/idle: Use explicit broadcast oneshot control function

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Message-ID: <553F6424.1090704@arm.com>
Date:	Tue, 28 Apr 2015 11:42:44 +0100
From:	Sudeep Holla <sudeep.holla@....com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>
CC:	Sudeep Holla <sudeep.holla@....com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH 16/20] sched/idle: Use explicit broadcast oneshot control
 function



On 28/04/15 11:34, Daniel Lezcano wrote:
> On 04/28/2015 12:11 PM, Linus Walleij wrote:
>> On Thu, Apr 2, 2015 at 12:22 AM, Rafael J. Wysocki
>> <rjw@...ysocki.net> wrote:
>>
>>> From: Thomas Gleixner <tglx@...utronix.de>
>>>
>>> Replace the clockevents_notify() call with an explicit function
>>> call.
>>>
>>> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
>>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>
>> For some reason this makes my Ux500 system arbitrarily hang,
>> especially during boot. Bisected down to this commit. Since the
>> entire changeset is removing the notifications altogether I can't
>> just revert it.
>>
>> Disabling CONFIG_CPU_IDLE removes the problem.
>>
>> Tried registering a stub driver (I just #if 0 all the code in
>> drivers/cpuidle/cpuidle-ux500.c) it still crashes.
>>
>> That makes me think something inside the cpuidle subsystem is
>> locking up after this, but my other idea is that the timer may be
>> involved in some way, like this is stressing the timer in some new
>> yet untested way.
>>
>> Has anyone else seen problems with this or is it only ux500?
>>
>> I'm looking closer at it but feel a bit clueless...
>
> If you keep the #if 0 and remove the CPUIDLE_FLAG_TIMER_STOP flag,
> does it still crash ?
>

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.

Regards,
Sudeep
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