From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: Re: [PATCH] cgroup: Show control files in cgroup2 root after mount Date: Tue, 18 Jul 2017 16:29:40 -0400 Message-ID: <255cc198-2c10-af76-98ca-086807d11540@redhat.com> References: <1500406336-29512-1-git-send-email-longman@redhat.com> <20170718195148.GC3365493@devbig577.frc2.facebook.com> <539870d2-8b85-2f54-61bd-4ba068e75ce0@redhat.com> <20170718201229.GD3365493@devbig577.frc2.facebook.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8BIT Return-path: DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 8ABE27F408 In-Reply-To: <20170718201229.GD3365493@devbig577.frc2.facebook.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Tejun Heo Cc: Li Zefan , Johannes Weiner , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org On 07/18/2017 04:12 PM, Tejun Heo wrote: > Hello, > > On Tue, Jul 18, 2017 at 04:00:45PM -0400, Waiman Long wrote: >> From my own debugging, the controller files (e.g. the debug controller) >> were indirectly populated by the rebind_subsystems() call. >> >> [ 1.628103] css_populate_dir: init subsystem debug > ... >> [ 1.654975] cgroup_apply_control_enable+0x103/0x340 >> [ 1.657719] cgroup_apply_control+0x1a/0x30 >> [ 1.658521] rebind_subsystems+0x18a/0x3b0 > ... > > But there's kernfs_activate() call at the end of rebind_subsystems(), > so if the files were being added there, it should have been activated > there and I can confirm that the files are correctly added / removed > from the cgroup2 root directory when controllers are attached to / > detached from it. I think the kernfs_activate() call is for the cgroup1 mount of debug cgroup which probably failed as I put debug in the cgroup_no_v1= option. The RHEL7 system that I ran the test on tried to do v1-mount of all the cgroup controllers available. I am also wondering how a v1-mount of debug controller will make the controller files appear on cgroup2 root. Maybe I miss something in the code. >> For the default cgroup2 root, kernfs_activate() was only called at the >> beginning in cgroup_init() with only the base cgroup files added. No >> more call after that until I touched the cgroup.subtree_control file. > Hmm... we're activating at the end of > > * cgroup_setup_root() > * rebind_subsystems() > * cgroup_subtree_control_write() > * cgroup_apply_cftypes() after successful addition > * cgroup_mkdir() > > I *think* this should cover everything. Just in case, are you looking > at the mainline kernel? Can you share how you can reproduce the > issue? My test kernel was built out of your latest cgroup git tree with the thread mode patches on (review-cgroup2-threads-v3 branch). As I said above, I put in the kernel command line option "cgroup_no_v1=pids,debug,memory". Then I mounted the cgroup2 filesystem after boot. # mount -t cgroup2 cgroup2 /cgroup2 # ls /cgroup2/ cgroup.controllers cgroup.procs cgroup.subtree_control cgroup.threads # echo +memory > /cgroup2/cgroup.subtree_control # ls /cgroup2/ cgroup.controllers debug.current_css_set cgroup.procs debug.current_css_set_cg_links cgroup.subtree_control debug.current_css_set_refcount cgroup.threads debug.masks debug.csses debug.taskcount debug.css_links Cheers, Longman