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From: Chris Hyser <chris.hyser@oracle.com>
To: Peter Zijlstra <peterz@infradead.org>,
	joel@joelfernandes.org, joshdon@google.com, mingo@kernel.org,
	vincent.guittot@linaro.org, valentin.schneider@arm.com,
	mgorman@suse.de
Cc: linux-kernel@vger.kernel.org, tj@kernel.org, tglx@linutronix.de
Subject: Re: [PATCH 4/9] sched: Default core-sched policy
Date: Wed, 21 Apr 2021 10:31:06 -0400	[thread overview]
Message-ID: <663c45ee-e946-961a-d850-fc75d11a357d@oracle.com> (raw)
In-Reply-To: <YIApkMU+2jZHUVD7@hirez.programming.kicks-ass.net>

On 4/21/21 9:33 AM, Peter Zijlstra wrote:
> On Thu, Apr 01, 2021 at 03:10:16PM +0200, Peter Zijlstra wrote:
>> Implement default core scheduling policy.
>>
>>   - fork() / clone(): inherit cookie from parent
>>   - exec(): if cookie then new cookie
>>
>> Did that exec() thing want to change cookie on suid instead, just like
>> perf_event_exit_task() ?
> 
> Talk to me about that exec() thing; I still think it's weird. Did we
> just want to drop cookie on suid instead?
> 

The choices for fork and exec were for security. A forked process or thread gets a copy because the code is "trusted", 
but execed code is not by default (that was the policy choice) and so it gets a new cookie. Dropping the cookie on suid 
was not considered (an oversight on my part), but seems like a good idea, but I think, also orthogonal.

The biggest issue with a new cookie on exec is that makes it difficult to construct a large process tree of all the same 
cookies like the cgroup interface does. If we remove the cgroup interface, we either need to remove the "new cookie on 
exec" (inherit cookie from parent from fork) or provide a global/per-task policy for controlling that. Probably easiest 
to just drop it.

-chrish

  reply	other threads:[~2021-04-21 14:31 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-01 13:10 [PATCH 0/9] sched: Core scheduling interfaces 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 [this message]
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
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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