From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Zefan Subject: Re: [PATCHSET cgroup/for-3.16] cgroup: iterate cgroup_subsys_states directly Date: Wed, 14 May 2014 12:21:25 +0800 Message-ID: <5372EF45.8060701@huawei.com> References: <1399671091-23867-1-git-send-email-tj@kernel.org> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1399671091-23867-1-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Tejun Heo Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org Hi Tejun, On 2014/5/10 5:31, Tejun Heo wrote: > Hello, > > Currently, while csses (cgroup_subsys_states) have ->parent linkage > too, only cgroups form full tree through their ->children and > ->sibling fields and css iterations naturally is implemented by > iterating cgroups and then dereferencing the css for the specified > subsystem. > > There are now use cases where controllers need to iterate through > csses regardless of their online state as long as they have positive What use cases are we talking about here? > reference. This can't easily be achieved by iterating cgroups because > its css pointer array needs to be cleared on offline and there may be > multiple dying csses for a cgroup for the same subsystem and there's > only one pointer per cgroup-subsystem pair. >