On 2013/1/4 5:35, Tejun Heo wrote: > Hello, guys. > > This is the second attempt at decoupling cpuset locking from cgroup > core. Changes from the last take[L] are > > * cpuset-drop-async_rebuild_sched_domains.patch moved from 0007 to > 0009. This reordering makes cpu hotplug handling async first and > removes the temporary cyclic locking dependency. > > * 0006-cpuset-cleanup-cpuset-_can-_attach.patch no longer converts > cpumask_var_t to cpumask_t as per Rusty Russell. > > * 0008-cpuset-don-t-nest-cgroup_mutex-inside-get_online_cpu.patch now > synchronously rebuilds sched domains from cpu hotplug callback. > This fixes various issues caused by confused scheduler puttings > tasks into a dead cpu including the RCU stall problem reported by Li > Zefan. > > Original patchset description follows. > > 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-reorganize-CPU-memory-hotplug-handling.patch > 0008-cpuset-don-t-nest-cgroup_mutex-inside-get_online_cpu.patch > 0009-cpuset-drop-async_rebuild_sched_domains.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 v3.8-rc2 (d1c3ed669a) 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 | 760 ++++++++++++++++++++++++++++++++------------------------ > 1 file changed, 438 insertions(+), 322 deletions(-) I've reviewed and tested the patchset, and it looks good to me! Acked-by: Li Zefan <lizefan@xxxxxxxxxx> -- 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>