Re: [PATCH 2/2] sched: Don't report SCHED_FLAG_SUGOV in sched_getattr()

From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Juri Lelli <juri.lelli@redhat.com>, Quentin Perret <qperret@google.com>
Cc: Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] sched: Don't report SCHED_FLAG_SUGOV in sched_getattr()
Date: Thu, 29 Jul 2021 19:21:03 +0200	[thread overview]
Message-ID: <97c06d07-bb6a-e8b5-b230-390edd8bcfbe@arm.com> (raw)
In-Reply-To: <YQFPYIqJG5PSPH1S@localhost.localdomain>

On 28/07/2021 14:36, Juri Lelli wrote:
> On 28/07/21 10:39, Quentin Perret wrote:
>> On Wednesday 28 Jul 2021 at 11:12:03 (+0200), Juri Lelli wrote:

[...]

>>> Maybe we can do this in the previous patch so that it's kept confined to
>>> deadline bits?
>>
>> That works too, it just felt like this could happen again if we start
>> using non-standard flags outside of deadline for any reason at some
>> point in the future. But no strong opinion really.
> 
> Yeah, I also see this point. :)
> 
> So no prob with me to keep it in core.c as you do here.
> 
> Best,
> Juri
> 

I would vote for not exporting SCHED_FLAG_SUGOV from __getparam_dl() in
patch 1/2 to underpin the idea that this flag is a hack.

@ -2759,7 +2759,7 @@ void __getparam_dl(struct task_struct *p, struct
sched_attr *attr)
        attr->sched_deadline = dl_se->dl_deadline;
        attr->sched_period = dl_se->dl_period;
        attr->sched_flags &= ~SCHED_DL_FLAGS;
-       attr->sched_flags |= dl_se->flags;
+       attr->sched_flags |= dl_se->flags & ~SCHED_FLAG_SUGOV;