linux-kernel - Re: [PATCH] cgroup: disable irqs while holding css_set

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Date:	Tue, 7 Jun 2016 12:26:42 -0300
From:	Daniel Bristot de Oliveira <daolivei@...hat.com>
To:	Juri Lelli <juri.lelli@....com>,
	Daniel Bristot de Oliveira <daolivei@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Rik van Riel <riel@...hat.com>,
	"Luis Claudio R. Goncalves" <lgoncalv@...hat.com>,
	Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
	Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org
Subject: Re: [PATCH] cgroup: disable irqs while holding css_set_lock

Ciao Juri,

On 06/07/2016 10:30 AM, Juri Lelli wrote:
> So, this and the partitioned one could actually overlap, since we don't
> set cpu_exclusive. Is that right?
> 
> I guess affinity mask of both m processes gets set correclty, but I'm
> not sure if we are missing one check in the admission control. Can you
> actually create two overlapping sets and get DEADLINE tasks running in
> them? For example, what happens if partitioned is [4] and clustered is
> [4-7]? Does setattr() fail?

That is what I was trying to understand/break. Fortunately, I still
can't break it! bravo! :-)

In the test you mentioned the task in the "clustered" fails to
sched_setattr().

Test output example:
+ '[' '!' -d partitioned ']'
+ mkdir partitioned
+ echo 4
+ echo 0
+ echo 0
+ echo 1155
+ cat /proc/self/cpuset
/partitioned
+ /root/m
main thread [1162]
deadline thread started [1164]
+ '[' '!' -d clustered ']'
+ mkdir clustered
+ echo 4-7
+ echo 0
+ echo 0
+ echo 1
+ echo 1155
+ cat /proc/self/cpuset
+ /root/m
/clustered
+ /root/m
main thread [1166]
sched_setattr: Operation not permitted

I will let you know if I find something odd.

-- Daniel