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authorTejun Heo <tj@kernel.org>2015-09-11 15:00:19 -0400
committerTejun Heo <tj@kernel.org>2015-09-22 12:46:53 -0400
commit4530eddb59494b89650d6bcd980fc7f7717ad80c (patch)
tree0f6212afa2e7e0e4724c5f12644508f1a0baf138 /mm/memcontrol.c
parent3df9ca0a2b8b50db5a079ae9d97c5b55435e9a6c (diff)
cgroup, memcg, cpuset: implement cgroup_taskset_for_each_leader()
It wasn't explicitly documented but, when a process is being migrated, cpuset and memcg depend on cgroup_taskset_first() returning the threadgroup leader; however, this approach is somewhat ghetto and would no longer work for the planned multi-process migration. This patch introduces explicit cgroup_taskset_for_each_leader() which iterates over only the threadgroup leaders and replaces cgroup_taskset_first() usages for accessing the leader with it. This prepares both memcg and cpuset for multi-process migration. This patch also updates the documentation for cgroup_taskset_for_each() to clarify the iteration rules and removes comments mentioning task ordering in tasksets. v2: A previous patch which added threadgroup leader test was dropped. Patch updated accordingly. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Zefan Li <lizefan@huawei.com> Acked-by: Michal Hocko <mhocko@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org>
Diffstat (limited to 'mm/memcontrol.c')
-rw-r--r--mm/memcontrol.c17
1 files changed, 15 insertions, 2 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9f331402e502..33c8dad6830f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4828,7 +4828,7 @@ static int mem_cgroup_can_attach(struct cgroup_subsys_state *css,
{
struct mem_cgroup *memcg = mem_cgroup_from_css(css);
struct mem_cgroup *from;
- struct task_struct *p;
+ struct task_struct *leader, *p;
struct mm_struct *mm;
unsigned long move_flags;
int ret = 0;
@@ -4842,7 +4842,20 @@ static int mem_cgroup_can_attach(struct cgroup_subsys_state *css,
if (!move_flags)
return 0;
- p = cgroup_taskset_first(tset);
+ /*
+ * Multi-process migrations only happen on the default hierarchy
+ * where charge immigration is not used. Perform charge
+ * immigration if @tset contains a leader and whine if there are
+ * multiple.
+ */
+ p = NULL;
+ cgroup_taskset_for_each_leader(leader, tset) {
+ WARN_ON_ONCE(p);
+ p = leader;
+ }
+ if (!p)
+ return 0;
+
from = mem_cgroup_from_task(p);
VM_BUG_ON(from == memcg);