From: Tejun Heo Date: Tue, 13 Aug 2013 15:01:54 +0000 (-0400) Subject: cgroup: add cgroup_subsys_state->parent X-Git-Tag: v3.12-rc1~173^2~22 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0ae78e0bf10ac38ab53548e18383afc9997eca22;p=pandora-kernel.git cgroup: add cgroup_subsys_state->parent With the planned unified hierarchy, css's (cgroup_subsys_state) will be RCU protected and allowed to be attached and detached dynamically over the course of a cgroup's lifetime. This means that css's will stay accessible after being detached from its cgroup - the matching pointer in cgroup->subsys[] cleared - for ref draining and RCU grace period. cgroup core still wants to guarantee that the parent css is never destroyed before its children and css_parent() always returns the parent regardless of the state of the child css as long as it's accessible. This patch makes css's hold onto their parents and adds css->parent so that the parent css is never detroyed before its children and can be determined without consulting the cgroups. cgroup->dummy_css is also updated to point to the parent dummy_css; however, it doesn't need to worry about object lifetime as the parent cgroup is already pinned by the child. Signed-off-by: Tejun Heo Acked-by: Li Zefan --- Reading git-diff-tree failed