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

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Date:   Tue, 7 Dec 2021 09:38:54 +0800
From:   "Lihua (lihua, ran)" <hucool.lihua@...wei.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        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


在 2021/12/3 15:17, Greg KH 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>
>> ---
>> v1->v2:
>>    - call do_start_rt_bandwidth to reduce repetitive code.
>>    - use raw_spin_lock_irqsave to avoid deadlock on a timer context.
>> ---
>>   kernel/sched/rt.c | 23 ++++++++++++++++++-----
>>   1 file changed, 18 insertions(+), 5 deletions(-)
> <formletter>
>
> This is not the correct way to submit patches for inclusion in the
> stable kernel tree.  Please read:
>      https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
> for how to do this properly.
I did not CC: stable in the signed-off region，Is that so？
> </formletter>
> .