From 4530eddb59494b89650d6bcd980fc7f7717ad80c Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 11 Sep 2015 15:00:19 -0400 Subject: 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 Acked-by: Zefan Li Acked-by: Michal Hocko Cc: Johannes Weiner --- kernel/cgroup.c | 11 ----------- 1 file changed, 11 deletions(-) (limited to 'kernel/cgroup.c') diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 0be276ffe08a..7f4b85af03dc 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2217,13 +2217,6 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp, get_css_set(new_cset); rcu_assign_pointer(tsk->cgroups, new_cset); - - /* - * Use move_tail so that cgroup_taskset_first() still returns the - * leader after migration. This works because cgroup_migrate() - * ensures that the dst_cset of the leader is the first on the - * tset's dst_csets list. - */ list_move_tail(&tsk->cg_list, &new_cset->mg_tasks); /* @@ -2419,10 +2412,6 @@ static int cgroup_migrate(struct cgroup *cgrp, struct task_struct *leader, if (!cset->mg_src_cgrp) goto next; - /* - * cgroup_taskset_first() must always return the leader. - * Take care to avoid disturbing the ordering. - */ list_move_tail(&task->cg_list, &cset->mg_tasks); if (list_empty(&cset->mg_node)) list_add_tail(&cset->mg_node, &tset.src_csets); -- cgit v1.2.3