linux-kernel - Re: [PATCH v2 08/10] cpuset: allow to keep tasks in empty cpusets

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20130605205146.GI10693@mtj.dyndns.org>
Date:	Wed, 5 Jun 2013 13:51:46 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Li Zefan <lizefan@...wei.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>,
	Containers <containers@...ts.linux-foundation.org>
Subject: Re: [PATCH v2 08/10] cpuset: allow to keep tasks in empty cpusets

Hello, Li.

On Wed, Jun 05, 2013 at 05:16:59PM +0800, Li Zefan wrote:
> @@ -2092,11 +2183,13 @@ static void cpuset_propagate_hotplug_workfn(struct work_struct *work)
>  	mutex_unlock(&cpuset_mutex);
>  
>  	/*
> -	 * If @cs became empty, move tasks to the nearest ancestor with
> -	 * execution resources.  This is full cgroup operation which will
> +	 * If sane_behavior flag is set, we'll keep tasks in empty cpusets.
> +	 *
> +	 * Otherwise move tasks to the nearest ancestor with execution
> +	 *  resources.  This is full cgroup operation which will
>  	 * also call back into cpuset.  Should be done outside any lock.
>  	 */
> -	if (is_empty)
> +	if (!sane && is_empty)
>  		remove_tasks_in_empty_cpuset(cs);
>  
>  	/* the following may free @cs, should be the last operation */
> @@ -2171,6 +2264,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
>  		cpumask_copy(top_cpuset.cpus_allowed, &new_cpus);
>  		mutex_unlock(&callback_mutex);
>  		/* we don't mess with cpumasks of tasks in top_cpuset */
> +		update_tasks_cpumask_hier(&top_cpuset, false, NULL);
>  	}

I'm a little confused by the order of operation.  We now have two
different hierarchical walks for hotplug propagation, right?  I
suppose the above one is added because we now also need to update the
mask when cpus are being brought online?

I wonder whether it'd be possible to merge the two paths.  My
suspicion is that we probably don't need propagate_hotplug_work
anymore now that we can drop RCU read lock while doing the pre-order
walk.  What do you think?

Thanks.

-- 
tejun
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/