linux-kernel - Re: [PATCH v2, RESEND] sched/rt: Try to restart rt period timer when rt runtime exceeded

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Message-ID: <cbd33c29-2ca8-f8bf-d9b5-fe5527b189e4@huawei.com>
Date:   Mon, 6 Dec 2021 09:42:19 +0800
From:   "Lihua (lihua, ran)" <hucool.lihua@...wei.com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        <linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Subject: Re: [PATCH v2, RESEND] sched/rt: Try to restart rt period timer when
 rt runtime exceeded

Fixes: d0b27fa77854 ("sched: rt-group: synchonised bandwidth period")

---

Thanks for your review~~

在 2021/12/4 19:34, Peter Zijlstra 写道:
> On Fri, Dec 03, 2021 at 03:36:18AM +0000, Li Hua wrote:
>> When rt_runtime is modified from -1 to a valid control value, it may
>> cause the task to be throttled all the time. Operations like the following
>> will trigger the bug. E.g:
>> 1. echo -1 > /proc/sys/kernel/sched_rt_runtime_us
>> 2. Run a FIFO task named A that executes while(1)
>> 3. echo 950000 > /proc/sys/kernel/sched_rt_runtime_us
>>
>> When rt_runtime is -1, The rt period timer will not be activated when task
>> A enqueued. And then the task will be throttled after setting rt_runtime to
>> 950,000. The task will always be throttled because the rt period timer is
>> not activated.
>>
>> Reported-by: Hulk Robot <hulkci@...wei.com>
>> Signed-off-by: Li Hua <hucool.lihua@...wei.com>
> Thanks, do you think you can reply here with a Fixes: tag so I can add
> it?
> .