From: Tejun Heo Date: Mon, 5 Nov 2012 17:16:58 +0000 (-0800) Subject: cgroup: kill CSS_REMOVED X-Git-Tag: omap-for-v3.8/fixes-for-merge-window-v4-signed~57^2~47^2~6 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e93160803ffda2e67d9ff9cacb63bb6868c8398f;p=pandora-kernel.git cgroup: kill CSS_REMOVED CSS_REMOVED is one of the several contortions which were necessary to support css reference draining on cgroup removal. All css->refcnts which need draining should be deactivated and verified to equal zero atomically w.r.t. css_tryget(). If any one isn't zero, all refcnts needed to be re-activated and css_tryget() shouldn't fail in the process. This was achieved by letting css_tryget() busy-loop until either the refcnt is reactivated (failed removal attempt) or CSS_REMOVED is set (committing to removal). Now that css refcnt draining is no longer used, there's no need for atomic rollback mechanism. css_tryget() simply can look at the reference count and fail if it's deactivated - it's never getting re-activated. This patch removes CSS_REMOVED and updates __css_tryget() to fail if the refcnt is deactivated. As deactivation and removal are a single step now, they no longer need to be protected against css_tryget() happening from irq context. Remove local_irq_disable/enable() from cgroup_rmdir(). Note that this removes css_is_removed() whose only user is VM_BUG_ON() in memcontrol.c. We can replace it with a check on the refcnt but given that the only use case is a debug assert, I think it's better to simply unexport it. v2: Comment updated and explanation on local_irq_disable/enable() added per Michal Hocko. Signed-off-by: Tejun Heo Reviewed-by: Michal Hocko Reviewed-by: KAMEZAWA Hiroyuki Acked-by: Li Zefan Cc: Johannes Weiner Cc: Balbir Singh --- Reading git-diff-tree failed