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From:   Valentin Schneider <vschneid@redhat.com>
To:     Yajun Deng <yajun.deng@linux.dev>, mingo@redhat.com,
        peterz@infradead.org, juri.lelli@redhat.com,
        vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
        bristot@redhat.com
Cc:     linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] sched/rt: fix the case where sched_rt_period_us is
 negative
In-Reply-To: <fdfc0c8f6027c2071674d52f27f7d7da@linux.dev>
References: <xhsmhmtfh1ptb.mognet@vschneid.remote.csb>
 <20220512003945.610093-1-yajun.deng@linux.dev>
 <fdfc0c8f6027c2071674d52f27f7d7da@linux.dev>
Date:   Tue, 17 May 2022 15:48:46 +0100
Message-ID: <xhsmhk0ak1agh.mognet@vschneid.remote.csb>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On 17/05/22 01:55, Yajun Deng wrote:
> May 16, 2022 11:04 PM, "Valentin Schneider" <vschneid@redhat.com> wrote:
>>> },
>>> {
>>> .procname = "sched_rt_runtime_us",
>>> @@ -44,6 +45,8 @@ static struct ctl_table sched_rt_sysctls[] = {
>>> .maxlen = sizeof(int),
>>> .mode = 0644,
>>> .proc_handler = sched_rt_handler,
>>> + .extra1 = SYSCTL_NEG_ONE,
>>> + .extra2 = (void *)&sysctl_sched_rt_period,
>>
>> Per this, you could also remove the
>>
>> ((sysctl_sched_rt_runtime > sysctl_sched_rt_period) ||
>>
>> from sched_rt_global_validate(), no?
>>
>
> No, the extra2 just limit the maximum value of sysctl_sched_rt_runtime is sysctl_sched_rt_period, but not limit the minimum value of sysctl_sched_rt_period is sysctl_sched_rt_runtime. (sysctl_sched_rt_runtime > sysctl_sched_rt_period) can do both.

Gotcha.

> Its purpose is to return error earlier. Perhaps I should remove extra2 to avoid ambiguity.
>

It's probably better to only have the "pure" bounds in there yes.