linux-hardened/Documentation/cgroups
Tejun Heo ef9fe980c6 cgroup_freezer: implement proper hierarchy support
Up until now, cgroup_freezer didn't implement hierarchy properly.
cgroups could be arranged in hierarchy but it didn't make any
difference in how each cgroup_freezer behaved.  They all operated
separately.

This patch implements proper hierarchy support.  If a cgroup is
frozen, all its descendants are frozen.  A cgroup is thawed iff it and
all its ancestors are THAWED.  freezer.self_freezing shows the current
freezing state for the cgroup itself.  freezer.parent_freezing shows
whether the cgroup is freezing because any of its ancestors is
freezing.

freezer_post_create() locks the parent and new cgroup and inherits the
parent's state and freezer_change_state() applies new state top-down
using cgroup_for_each_descendant_pre() which guarantees that no child
can escape its parent's state.  update_if_frozen() uses
cgroup_for_each_descendant_post() to propagate frozen states
bottom-up.

Synchronization could be coarser and easier by using a single mutex to
protect all hierarchy operations.  Finer grained approach was used
because it wasn't too difficult for cgroup_freezer and I think it's
beneficial to have an example implementation and cgroup_freezer is
rather simple and can serve a good one.

As this makes cgroup_freezer properly hierarchical,
freezer_subsys.broken_hierarchy marking is removed.

Note that this patch changes userland visible behavior - freezing a
cgroup now freezes all its descendants too.  This behavior change is
intended and has been warned via .broken_hierarchy.

v2: Michal spotted a bug in freezer_change_state() - descendants were
    inheriting from the wrong ancestor.  Fixed.

v3: Documentation/cgroups/freezer-subsystem.txt updated.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
2012-11-09 10:52:30 -08:00
..
00-INDEX trivial: fix where cgroup documentation is not correctly referred to 2009-03-30 15:22:02 +02:00
blkio-controller.txt Documentation: Fix multiple typo in Documentation 2012-03-07 16:08:24 +01:00
cgroup_event_listener.c tree-wide: fix comment/printk typos 2010-11-01 15:38:34 -04:00
cgroups.txt cgroup: trivial fixes for Documentation/cgroups/cgroups.txt 2012-09-13 11:10:54 -07:00
cpuacct.txt Documentation: fix echo command in cgroups/cpuacct.txt 2011-07-23 10:58:08 -07:00
cpusets.txt documentation: remove references to cpu_*_map. 2012-03-29 15:38:31 +10:30
devices.txt Documentation: update cgroupfs mount point 2011-06-15 21:52:50 -07:00
freezer-subsystem.txt cgroup_freezer: implement proper hierarchy support 2012-11-09 10:52:30 -08:00
hugetlb.txt hugetlb/cgroup: add HugeTLB controller documentation 2012-07-31 18:42:41 -07:00
memcg_test.txt tree-wide: fix comment/printk typos 2010-11-01 15:38:34 -04:00
memory.txt memcg: trivial fixes for Documentation/cgroups/memory.txt 2012-10-09 16:22:54 +09:00
net_prio.txt net: add documentation for net_prio cgroups (v4) 2011-11-22 15:22:23 -05:00
resource_counter.txt rescounters: add res_counter_uncharge_until() 2012-05-29 16:22:27 -07:00