linux-kernel - Re: [PATCH] sched/core: Fix cpu controller for !RT_GROUP

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Message-ID: <20190619123405.GN26005@localhost.localdomain>
Date:   Wed, 19 Jun 2019 14:34:05 +0200
From:   Juri Lelli <juri.lelli@...hat.com>
To:     Michal Koutný <mkoutny@...e.com>
Cc:     peterz@...radead.org, mingo@...hat.com, rostedt@...dmis.org,
        lizefan@...wei.com, tj@...nel.org, bristot@...hat.com,
        luca.abeni@...tannapisa.it, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/core: Fix cpu controller for !RT_GROUP_SCHED

Hi,

On 19/06/19 11:29, Michal Koutný wrote:
> On Wed, Jun 05, 2019 at 04:20:03PM +0200, Michal Koutný <mkoutny@...e.com> wrote:
> > I considered relaxing the check to non-root cgroups only, however, as
> > your example shows, it doesn't prevent reaching the avoided state by
> > other paths. I'm not that familiar with RT sched to tell whether
> > RT-priority tasks in different task_groups break any assumptions.
> So I had another look and the check is bogus.
> 
> The RT sched with !CONFIG_RT_GROUP_SCHED works only with the struct
> rt_rq embedded in the generic struct rq -- regardless of the task's
> membership in the cpu controller hierarchy.

Yep.

> Perhaps, the commit message may mention this also prevents enabling cpu
> controller on unified hierarchy (if there are any (kernel) RT tasks to
> migrate).

Sure. Can add such a comment.

> Reviewed-by: Michal Koutný <mkoutny@...e.com>

Thanks!

Peter?

Best,

Juri