From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH 1/8] cgroup: kill cgroup_subsys->__DEPRECATED_clear_css_refs Date: Wed, 31 Oct 2012 15:37:51 +0100 Message-ID: <20121031143751.GA22809@dhcp22.suse.cz> References: <1351657365-25055-1-git-send-email-tj@kernel.org> <1351657365-25055-2-git-send-email-tj@kernel.org> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <1351657365-25055-2-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" Content-Transfer-Encoding: 7bit To: Tejun Heo Cc: lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, bsingharora-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org On Tue 30-10-12 21:22:38, Tejun Heo wrote: > 2ef37d3fe4 ("memcg: Simplify mem_cgroup_force_empty_list error > handling") removed the last user of __DEPRECATED_clear_css_refs. This > patch removes __DEPRECATED_clear_css_refs and mechanisms to support > it. > > * Conditionals dependent on __DEPRECATED_clear_css_refs removed. > > * ->pre_destroy() now can only fail if a new task is attached or child > cgroup is created while ->pre_destroy()s are being called. As the > condition is checked again after re-acquiring cgroup_mutex > afterwards, we don't need to take any immediate action on > ->pre_destroy() failures. This reduces cgroup_call_pre_destroy() to > a simple loop surrounding ->pre_destory(). Remove > cgroup_call_pre_destroy() and open-code the loop into > cgroup_rmdir(). > > * cgroup_clear_css_refs() can no longer fail. All that needs to be > done are deactivating refcnts, setting CSS_REMOVED and putting the > base reference on each css. Remove cgroup_clear_css_refs() and the > failure path, and open-code the loops into cgroup_rmdir(). > > Note that cgroup_rmdir() will see more cleanup soon. > > Signed-off-by: Tejun Heo Looks good to me and the diffstat is really encouraging Reviewed-by: Michal Hocko with a minor note bellow > --- > include/linux/cgroup.h | 12 ---- > kernel/cgroup.c | 159 ++++++++++++------------------------------------- > 2 files changed, 38 insertions(+), 133 deletions(-) [...] > diff --git a/kernel/cgroup.c b/kernel/cgroup.c > index 7981850..033bf4b 100644 > --- a/kernel/cgroup.c > +++ b/kernel/cgroup.c [...] > @@ -4168,11 +4075,9 @@ again: > * Call pre_destroy handlers of subsys. Notify subsystems > * that rmdir() request comes. > */ > - ret = cgroup_call_pre_destroy(cgrp); > - if (ret) { > - clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags); > - return ret; > - } > + for_each_subsys(cgrp->root, ss) > + if (ss->pre_destroy) > + WARN_ON_ONCE(ss->pre_destroy(cgrp)); Hmm, I am not sure I like this WARN_ON_ONCE. First it can happen for more than one controller and second we can just clear CGRP_WAIT_ON_RMDIR and return with EBUSY. The only possible failure at the moment is when a new task or a child group appear. I know it is not a big deal because it will disappear later in the series but it would be more readable IMO. Thanks! -- Michal Hocko SUSE Labs