From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: paulmck@linux.vnet.ibm.com
Cc: Viresh Kumar <viresh.kumar@linaro.org>,
"Rafael J. Wysocki" <rjw@sisk.pl>,
Lists linaro-kernel <linaro-kernel@lists.linaro.org>,
Patch Tracking <patches@linaro.org>,
"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 19/21] cpuidle: create list of registered drivers
Date: Mon, 30 Sep 2013 20:37:47 +0200 [thread overview]
Message-ID: <5249C4FB.1060705@linaro.org> (raw)
In-Reply-To: <20130928213343.GA19582@linux.vnet.ibm.com>
On 09/28/2013 11:33 PM, Paul E. McKenney wrote:
> On Thu, Sep 26, 2013 at 10:19:14AM +0200, Daniel Lezcano wrote:
>> On 09/26/2013 08:17 AM, Viresh Kumar wrote:
>>> On 26 September 2013 04:00, Daniel Lezcano <daniel.lezcano@linaro.org> wrote:
>>>> If you introduce a list, you will have to introduce a lock to protect
>>>> it.
>>>
>>> I missed it, should have added that :)
>>>
>>>> This lock will be in the fast path cpuidle_idle_call with the
>>>> get_driver function and conforming to the comment: "NOTE: no locks or
>>>> semaphores should be used here".
>>>>
>>>> A lock has been introduced in this function already and the system hangs
>>>> with 1024 cpus.
>>>
>>> Hmm... I see.. I didn't knew about this expectation.. What about a rcu
>>> read/write lock? As far as I know its too lightweight... Can we have that
>>> in fast path?
>>
>> Nope, we can't use rcu in the idle path :)
>>
>> http://lists.infradead.org/pipermail/linux-arm-kernel/2012-February/083054.html
>
> But you should be able to use SRCU in the idle path, if that helps.
Interesting, thanks for the pointer.
-- Daniel
--
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next prev parent reply other threads:[~2013-09-30 18:37 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-22 1:20 [PATCH 00/21] CPUIdle: Minor cleanups for 3.13 Viresh Kumar
2013-09-22 1:20 ` [PATCH 01/21] cpuidle: fix indentation of cpumask Viresh Kumar
2013-09-22 1:20 ` [PATCH 02/21] cpuidle: Fix comments in cpuidle core Viresh Kumar
2013-09-22 1:20 ` [PATCH 03/21] cpuidle: make __cpuidle_get_cpu_driver() inline Viresh Kumar
2013-09-25 21:27 ` Daniel Lezcano
2013-09-22 1:20 ` [PATCH 04/21] cpuidle: make __cpuidle_device_init() return void Viresh Kumar
2013-09-22 1:20 ` [PATCH 05/21] cpuidle: make __cpuidle_driver_init() " Viresh Kumar
2013-09-23 9:58 ` Hongbo Zhang
2013-09-23 9:58 ` Hongbo Zhang
2013-09-23 10:02 ` Viresh Kumar
2013-09-22 1:20 ` [PATCH 06/21] cpuidle: rearrange code in __cpuidle_driver_init() Viresh Kumar
2013-09-25 21:40 ` Daniel Lezcano
2013-09-26 5:01 ` Viresh Kumar
2013-09-22 1:20 ` [PATCH 07/21] cpuidle: rearrange __cpuidle_register_device() to keep minimal exit points Viresh Kumar
2013-09-25 21:49 ` Daniel Lezcano
2013-09-22 1:21 ` [PATCH 08/21] cpuidle: use cpuidle_disabled() instead of "off" Viresh Kumar
2013-09-25 21:52 ` Daniel Lezcano
2013-09-26 5:06 ` Viresh Kumar
2013-09-26 8:25 ` Daniel Lezcano
2013-09-22 1:21 ` [PATCH 09/21] cpuidle: merge two if() statements for checking error cases Viresh Kumar
2013-09-25 21:52 ` Daniel Lezcano
2013-09-22 1:21 ` [PATCH 10/21] cpuidle: reduce code duplication inside cpuidle_idle_call() Viresh Kumar
2013-09-25 22:01 ` Daniel Lezcano
2013-09-22 1:21 ` [PATCH 11/21] cpuidle: replace multiline statements with single line in cpuidle_idle_call() Viresh Kumar
2013-09-25 22:03 ` Daniel Lezcano
2013-09-26 5:51 ` Viresh Kumar
2013-09-26 7:55 ` Daniel Lezcano
2013-09-26 8:11 ` Viresh Kumar
2013-09-22 1:21 ` [PATCH 12/21] cpuidle: call cpuidle_get_driver() from after taking cpuidle_driver_lock Viresh Kumar
2013-09-25 22:04 ` Daniel Lezcano
2013-09-22 1:21 ` [PATCH 13/21] cpuidle: use drv instead of cpuidle_driver in show_current_driver() Viresh Kumar
2013-09-25 22:05 ` Daniel Lezcano
2013-09-22 1:21 ` [PATCH 14/21] cpuidle: coupled: don't compare cpu masks unnecessarily Viresh Kumar
2013-09-25 22:06 ` Daniel Lezcano
2013-09-26 0:25 ` Colin Cross
2013-09-26 6:36 ` Viresh Kumar
2013-09-26 6:50 ` Colin Cross
2013-09-22 1:21 ` [PATCH 15/21] cpuidle: free all state kobjects from cpuidle_free_state_kobj() Viresh Kumar
2013-09-25 22:09 ` Daniel Lezcano
2013-09-22 1:21 ` [PATCH 16/21] cpuidle: avoid unnecessary kzalloc/free of struct cpuidle_device_kobj Viresh Kumar
2013-09-25 22:12 ` Daniel Lezcano
2013-09-26 6:05 ` Viresh Kumar
2013-09-26 8:30 ` Daniel Lezcano
2013-09-22 1:21 ` [PATCH 17/21] cpuidle: avoid unnecessary kzalloc/free of struct cpuidle_driver_kobj Viresh Kumar
2013-09-25 22:16 ` Daniel Lezcano
2013-09-22 1:21 ` [PATCH 18/21] cpuidle: don't call poll_idle_init() for every cpu Viresh Kumar
2013-09-25 22:22 ` Daniel Lezcano
2013-09-26 6:09 ` Viresh Kumar
2013-09-26 8:28 ` Daniel Lezcano
2013-10-03 10:33 ` Viresh Kumar
2013-10-03 11:46 ` Daniel Lezcano
2013-09-22 1:21 ` [PATCH 19/21] cpuidle: create list of registered drivers Viresh Kumar
2013-09-25 22:30 ` Daniel Lezcano
2013-09-26 6:17 ` Viresh Kumar
2013-09-26 8:19 ` Daniel Lezcano
2013-09-28 21:33 ` Paul E. McKenney
2013-09-30 18:37 ` Daniel Lezcano [this message]
2013-10-03 4:38 ` Viresh Kumar
2013-10-03 10:47 ` Daniel Lezcano
2013-09-22 1:21 ` [PATCH 20/21] cpuidle: don't calculate time-diff if entered_state == 0 Viresh Kumar
2013-09-25 22:38 ` Daniel Lezcano
2013-09-26 6:24 ` Viresh Kumar
2013-09-26 8:25 ` Daniel Lezcano
2013-09-26 8:28 ` Viresh Kumar
2013-09-26 8:33 ` Daniel Lezcano
2013-09-22 1:21 ` [PATCH 21/21] cpuidle: change governor from within cpuidle_replace_governor() Viresh Kumar
2013-09-25 22:50 ` Daniel Lezcano
2013-09-26 6:37 ` Viresh Kumar
2013-09-26 8:20 ` Daniel Lezcano
2013-10-03 10:36 ` Viresh Kumar
2013-10-03 11:58 ` Daniel Lezcano
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