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From: Peter Zijlstra <peterz@infradead.org>
To: Tejun Heo <tj@kernel.org>
Cc: joel@joelfernandes.org, chris.hyser@oracle.com,
	joshdon@google.com, mingo@kernel.org, vincent.guittot@linaro.org,
	valentin.schneider@arm.com, mgorman@suse.de,
	linux-kernel@vger.kernel.org, tglx@linutronix.de,
	"Michal Koutný" <mkoutny@suse.com>,
	"Christian Brauner" <christian.brauner@ubuntu.com>,
	"Zefan Li" <lizefan.x@bytedance.com>
Subject: Re: [PATCH 0/9] sched: Core scheduling interfaces
Date: Wed, 7 Apr 2021 20:39:40 +0200	[thread overview]
Message-ID: <YG38bBm+JJXIwgYq@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <YGyHknFJhHO99e5a@slm.duckdns.org>

On Tue, Apr 06, 2021 at 12:08:50PM -0400, Tejun Heo wrote:

> I see. Yeah, if we really need it, I'm not sure it fits in cgroup interface
> proper. As I wrote elsewhere, these things are usually implemented on the
> originating subsystem interface with cgroup ID as a parameter.

This would be something like:

  prctl(PR_SCHED_CORE, PR_SCHED_CORE_SHARE_FROM, cgroup-fd, PIDTYPE_CGROUP, NULL);

right? Where we assign to self the cookie from the cgroup.

The problem I see with this is that a task can trivially undo/circumvent
this by calling PR_SCHED_CORE_CLEAR on itself, at which point it can
share with system tasks again.

Also, it doesn't really transfer well to the group/tasks thing. When a
task joins a cgroup, it doesn't automagically gain the cgroup
properties. Whoever does the transition will then also have to prctl()
this, which nobody will do.


  reply	other threads:[~2021-04-07 18:41 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-01 13:10 Peter Zijlstra
2021-04-01 13:10 ` [PATCH 1/9] sched: Allow sched_core_put() from atomic context Peter Zijlstra
2021-04-01 13:10 ` [PATCH 2/9] sched: Implement core-sched assertions Peter Zijlstra
2021-04-01 13:10 ` [PATCH 3/9] sched: Trivial core scheduling cookie management Peter Zijlstra
2021-04-01 20:04   ` Josh Don
2021-04-02  7:13     ` Peter Zijlstra
2021-04-01 13:10 ` [PATCH 4/9] sched: Default core-sched policy Peter Zijlstra
2021-04-21 13:33   ` Peter Zijlstra
2021-04-21 14:31     ` Chris Hyser
2021-04-01 13:10 ` [PATCH 5/9] sched: prctl() core-scheduling interface Peter Zijlstra
2021-04-07 17:00   ` Peter Zijlstra
2021-04-18  3:52     ` Joel Fernandes
2021-04-01 13:10 ` [PATCH 6/9] kselftest: Add test for core sched prctl interface Peter Zijlstra
2021-04-01 13:10 ` [PATCH 7/9] sched: Cgroup core-scheduling interface Peter Zijlstra
2021-04-02  0:34   ` Josh Don
2021-04-01 13:10 ` [PATCH 8/9] rbtree: Remove const from the rb_find_add() comparator Peter Zijlstra
2021-04-01 13:10 ` [PATCH 9/9] sched: prctl() and cgroup interaction Peter Zijlstra
2021-04-03  1:30   ` Josh Don
2021-04-06 15:12     ` Peter Zijlstra
2021-04-04 23:39 ` [PATCH 0/9] sched: Core scheduling interfaces Tejun Heo
2021-04-05 18:46   ` Joel Fernandes
2021-04-06 14:16     ` Tejun Heo
2021-04-18  1:35       ` Joel Fernandes
2021-04-19  9:00         ` Peter Zijlstra
2021-04-21 13:35           ` Peter Zijlstra
2021-04-21 14:45             ` Chris Hyser
2021-04-06 15:32   ` Peter Zijlstra
2021-04-06 16:08     ` Tejun Heo
2021-04-07 18:39       ` Peter Zijlstra [this message]
2021-04-07 16:50   ` Michal Koutný
2021-04-07 18:34     ` Peter Zijlstra
2021-04-08 13:25       ` Michal Koutný
2021-04-08 15:02         ` Peter Zijlstra
2021-04-09  0:16           ` Josh Don
2021-04-19 11:30       ` Tejun Heo
2021-04-20  1:17         ` Josh Don

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