linux-kernel - Re: [PATCH V3 2/2] sched: idle: IRQ based next prediction for idle period

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <56CC2F90.4040008@linux.vnet.ibm.com>
Date:	Tue, 23 Feb 2016 15:38:16 +0530
From:	Shreyas B Prabhu <shreyas@...ux.vnet.ibm.com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
CC:	tglx@...utronix.de, peterz@...radead.org, rafael@...nel.org,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	nicolas.pitre@...aro.org, vincent.guittot@...aro.org
Subject: Re: [PATCH V3 2/2] sched: idle: IRQ based next prediction for idle
 period



On 02/22/2016 10:59 PM, Daniel Lezcano wrote:
> On 02/22/2016 04:02 PM, Shreyas B Prabhu wrote:
>> Hi Daniel,
>>
>> On 02/16/2016 09:13 PM, Daniel Lezcano wrote:
>>> +
>>> +/**
>>> + * sched_idle_next_wakeup - Predict the next wakeup on the current cpu
>>> + *
>>> + * The next event on the cpu is based on a statistic approach of the
>>> + * interrupt events and the timer deterministic value. From the timer
>>> + * or the irqs, we return the one expected to occur first.
>>> + *
>>> + * Returns the expected remaining idle time before being woken up by
>>> + * an interruption.
>>> + */
>>> +s64 sched_idle_next_wakeup(void)
>>> +{
>>> +    s64 next_timer = ktime_to_us(tick_nohz_get_sleep_length());
>>> +    s64 next_irq = next_irq_event();
>>
>> Since next_irq_event() uses RCU and we are in idle this should probably
>> be wrapped in RCU_NONIDLE().
> 
> That is a good point but the function is not supposed to be called in
> the rcu_idle_enter/rcu_idle_exit section which is inside
> cpuidle_idle_call().
> 
> 
Right. My bad.