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| author | Tejun Heo <tj@kernel.org> | 2015-09-11 22:00:19 +0300 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2015-09-22 19:46:53 +0300 |
| commit | 4530eddb59494b89650d6bcd980fc7f7717ad80c (patch) | |
| tree | 0f6212afa2e7e0e4724c5f12644508f1a0baf138 /include/linux/cgroup.h | |
| parent | 3df9ca0a2b8b50db5a079ae9d97c5b55435e9a6c (diff) | |
| download | linux-4530eddb59494b89650d6bcd980fc7f7717ad80c.tar.xz | |
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 'include/linux/cgroup.h')
| -rw-r--r-- | include/linux/cgroup.h | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index fb717f2cba5b..e9c3eac074e2 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -232,11 +232,33 @@ void css_task_iter_end(struct css_task_iter *it); * cgroup_taskset_for_each - iterate cgroup_taskset * @task: the loop cursor * @tset: taskset to iterate + * + * @tset may contain multiple tasks and they may belong to multiple + * processes. When there are multiple tasks in @tset, if a task of a + * process is in @tset, all tasks of the process are in @tset. Also, all + * are guaranteed to share the same source and destination csses. + * + * Iteration is not in any specific order. */ #define cgroup_taskset_for_each(task, tset) \ for ((task) = cgroup_taskset_first((tset)); (task); \ (task) = cgroup_taskset_next((tset))) +/** + * cgroup_taskset_for_each_leader - iterate group leaders in a cgroup_taskset + * @leader: the loop cursor + * @tset: takset to iterate + * + * Iterate threadgroup leaders of @tset. For single-task migrations, @tset + * may not contain any. + */ +#define cgroup_taskset_for_each_leader(leader, tset) \ + for ((leader) = cgroup_taskset_first((tset)); (leader); \ + (leader) = cgroup_taskset_next((tset))) \ + if ((leader) != (leader)->group_leader) \ + ; \ + else + /* * Inline functions. */ |