Hello, guys. Changes from the last posting[L] are, * cgroup_call_pre_destroy() removal moved from 0001 to 0004 per Michal. * Comment and commit message updates per Glauber and Michal. Original head message follows. cgroup removal path is quite ugly. A lot of the ugliness comes from the weird design which allows ->pre_destroy() to fail and the feature to drain existing CSS reference counts before committing to removal. Both mean that it should be possible to roll-back cgroup destruction after some or all ->pre_destroy() invocations. This weird design has never really worked. To list a couple examples. * Some ->pre_destroy() implementations aren't side-effect free. Roll-back happens after a lot of state is already lost. * Some ->pre_destroy() implementations (naturally) assume that the cgroup being destroyed would stay quiescent between successful ->pre_destroy() and its destruction. Unfortunately, any operation can happen inbetween and the cgroup could be in a very different state by the time it actually gets destroyed. It's just such an unusual design which unnecessarily contains weird code path combinations which are tricky to hit, reproduce and expect. Moreover, the design's deficiencies attracts kludges on top as workarounds and we end up with stuff like cgroup_exclude_rmdir() and cgroup_release_and_wakeup_rmdir() which really make me want to cry. Now that memcg has moved away from failable ->pre_destroy(), we can do away with all these. I tested some basic operations and some corner cases but am still a bit scared. Would love to get acks from Li and memcg people. This patchset contains the following eight patches. 0001-cgroup-kill-cgroup_subsys-__DEPRECATED_clear_css_ref.patch 0002-cgroup-kill-CSS_REMOVED.patch 0003-cgroup-use-cgroup_lock_live_group-parent-in-cgroup_c.patch 0004-cgroup-deactivate-CSS-s-and-mark-cgroup-dead-before-.patch 0005-cgroup-remove-CGRP_WAIT_ON_RMDIR-cgroup_exclude_rmdi.patch 0006-memcg-make-mem_cgroup_reparent_charges-non-failing.patch 0007-hugetlb-do-not-fail-in-hugetlb_cgroup_pre_destroy.patch 0008-cgroup-make-pre_destroy-return-void.patch 0001-0002 remove now unused ->pre_destroy() failure handling and do follow-up simplification. 0003-0004 update removal path such that each ->pre_destroy() is guaranteed to be invoked once per removal and the cgroup being destroyed stays quiescent until destruction is complete. 0005 removes the scary CGRP_WAIT_ON_RMDIR mechanism. 0006-0008 are follow-up clean-ups. 0006 and 0007 are from Michal's patchset[1]. This patchset is on top of v3.6 (a0d271cbfe) + [1] the first three patches of "memcg/cgroup: do not fail fail on pre_destroy callbacks" patchset and available in the following git branch. git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git review-cgroup-rmdir-updates Thanks. block/blk-cgroup.c | 3 include/linux/cgroup.h | 41 ------- kernel/cgroup.c | 256 +++++++++++-------------------------------------- mm/hugetlb_cgroup.c | 11 -- mm/memcontrol.c | 51 +-------- 5 files changed, 75 insertions(+), 287 deletions(-) -- tejun [L] http://www.spinics.net/lists/linux-containers/msg26157.html [1] http://thread.gmane.org/gmane.linux.kernel.cgroups/4757 -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html