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

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Date:	Tue, 7 Jun 2016 09:39:13 -0300
From:	Daniel Bristot de Oliveira <daolivei@...hat.com>
To:	Juri Lelli <juri.lelli@....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 07:14 AM, Juri Lelli wrote:
> Interesting. And your test is using cpuset controller to partion
> DEADLINE tasks and then modify groups concurrently?

Yes. I was studying the partitioning/admission control of the
deadline scheduler, to document it.

I was using the minimal task from sched deadline's documentation
as the load (the ./m in the bellow script). 

Here is the script I was using in the test:
-----------%<------------------------------------------------------------
#!/bin/sh

# I am running on a 8 cpus box, you need to adjust the
# cpu mask to match to your cpu topology.

cd /sys/fs/cgroup/cpuset

# global settings
# echo 1 > cpuset.cpu_exclusive
echo 0 > cpuset.sched_load_balance

# a cpuset to run ordinary load:

if [ ! -d ordinary ]; then
	mkdir ordinary
	echo 0-3 > ordinary/cpuset.cpus
	echo 0 > ordinary/cpuset.mems
	echo 0 > ordinary/cpuset.cpu_exclusive
	# the load balance can be enabled on this cpuset.
	echo 1 > ordinary/cpuset.sched_load_balance
fi

# move all threads to ordinary cpuset 
ps -eL -o lwp | while read tid; do
	echo $tid >> ordinary/tasks 2> /dev/null || echo "thread $tid is pinned or died"
done

echo $$ > ordinary/tasks
cat /proc/self/cpuset
~/m &

# a single cpu cpuset (partitioned)
if [ ! -d partitioned ]; then
	mkdir partitioned
	echo 4 > partitioned/cpuset.cpus
	echo 0 > partitioned/cpuset.mems
	echo 0 > partitioned/cpuset.cpu_exclusive
fi

echo $$ > partitioned/tasks
cat /proc/self/cpuset
~/m &

# a set of cpus (clustered)
if [ ! -d clustered ]; then
	mkdir clustered
	echo 5-7 > clustered/cpuset.cpus
	echo 0 > clustered/cpuset.mems
	echo 0 > clustered/cpuset.cpu_exclusive
	# the load balance can be enabled on this cpuset.
	echo 1 > clustered/cpuset.sched_load_balance
fi

echo $$ > clustered/tasks
cat /proc/self/cpuset
~/m
----------->%------------------------------------------------------------

The problem rarely reproduces.

-- Daniel