Hello, guys. Depending on cgroup core locking - cgroup_mutex - is messy and makes cgroup prone to locking dependency problems. The current code already has lock dependency loop - memcg nests get_online_cpus() inside cgroup_mutex. cpuset the other way around. Regardless of the locking details, whatever is protecting cgroup has inherently to be something outer to most other locking constructs. cgroup calls into a lot of major subsystems which in turn have to perform subsystem-specific locking. Trying to nest cgroup synchronization inside other locks isn't something which can work well. cgroup now has enough API to allow subsystems to implement their own locking and cgroup_mutex is scheduled to be made private to cgroup core. This patchset makes cpuset implement its own locking instead of relying on cgroup_mutex. cpuset is rather nasty in this respect. Some of it seems to have come from the implementation history - cgroup core grew out of cpuset - but big part stems from cpuset's need to migrate tasks to an ancestor cgroup when an hotunplug event makes a cpuset empty (w/o any cpu or memory). This patchset decouples cpuset locking from cgroup_mutex. After the patchset, cpuset uses cpuset-specific cpuset_mutex instead of cgroup_mutex. This also removes the lockdep warning triggered during cpu offlining (see 0009). Note that this leaves memcg as the only external user of cgroup_mutex. Michal, Kame, can you guys please convert memcg to use its own locking too? This patchset contains the following thirteen patches. 0001-cpuset-remove-unused-cpuset_unlock.patch 0002-cpuset-remove-fast-exit-path-from-remove_tasks_in_em.patch 0003-cpuset-introduce-css_on-offline.patch 0004-cpuset-introduce-CS_ONLINE.patch 0005-cpuset-introduce-cpuset_for_each_child.patch 0006-cpuset-cleanup-cpuset-_can-_attach.patch 0007-cpuset-drop-async_rebuild_sched_domains.patch 0008-cpuset-reorganize-CPU-memory-hotplug-handling.patch 0009-cpuset-don-t-nest-cgroup_mutex-inside-get_online_cpu.patch 0010-cpuset-make-CPU-memory-hotplug-propagation-asynchron.patch 0011-cpuset-pin-down-cpus-and-mems-while-a-task-is-being-.patch 0012-cpuset-schedule-hotplug-propagation-from-cpuset_atta.patch 0013-cpuset-replace-cgroup_mutex-locking-with-cpuset-inte.patch 0001-0006 are prep patches. 0007-0009 make cpuset nest get_online_cpus() inside cgroup_mutex, not the other way around. 0010-0012 plug holes which would be exposed by switching to cpuset-specific locking. 0013 replaces cgroup_mutex with cpuset_mutex. This patchset is on top of cgroup/for-3.8 (fddfb02ad0) and also available in the following git branch. git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git review-cpuset-locking diffstat follows. kernel/cpuset.c | 750 +++++++++++++++++++++++++++++++------------------------- 1 file changed, 423 insertions(+), 327 deletions(-) Thanks. -- tejun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>