linux-kernel - Re: [PATCH 3/9] cgroup: implement generic child / descendant walk macros

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]

Date:	Wed, 7 Nov 2012 09:01:18 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	lizefan@...wei.com, rjw@...k.pl,
	containers@...ts.linux-foundation.org, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	fweisbec@...il.com
Subject: Re: [PATCH 3/9] cgroup: implement generic child / descendant walk
 macros

Hello, Michal.

On Wed, Nov 07, 2012 at 05:54:57PM +0100, Michal Hocko wrote:
> > +struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
> > +					  struct cgroup *cgroup)
> > +{
> > +	struct cgroup *next;
> > +
> > +	WARN_ON_ONCE(!rcu_read_lock_held());
> > +
> > +	/* if first iteration, pretend we just visited @cgroup */
> > +	if (!pos) {
> > +		if (list_empty(&cgroup->children))
> > +			return NULL;
> > +		pos = cgroup;
> > +	}
> 
> Is there any specific reason why the root of the tree is excluded?
> This is bit impractical because you have to special case the root
> in the code.

Yeah, thought about including it but decided against it for two
reasons.

* To be consistent with cgroup_for_each_children() - it's a bit weird
  for descendants to include self when children don't.

* Iteration root is likely to require different treatment anyway.
  e.g. for cgroup_freezer, the root is updated to the specified config
  while all the descendants inherit config from its immediate parent.
  They are different.

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/