cgroup: don't use subsys->can_attach_task() or ->attach_task()

Now that subsys->can_attach() and attach() take @tset instead of
@task, they can handle per-task operations.  Convert
->can_attach_task() and ->attach_task() users to use ->can_attach()
and attach() instead.  Most converions are straight-forward.
Noteworthy changes are,

* In cgroup_freezer, remove unnecessary NULL assignments to unused
  methods.  It's useless and very prone to get out of sync, which
  already happened.

* In cpuset, PF_THREAD_BOUND test is checked for each task.  This
  doesn't make any practical difference but is conceptually cleaner.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <paul@paulmenage.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: James Morris <jmorris@namei.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>

1 files changed, 19 insertions, 12 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 0e9344a71be3..161184da7b81 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -9127,24 +9127,31 @@ cpu_cgroup_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp)
 	sched_destroy_group(tg);
 }
 
-static int
-cpu_cgroup_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
+static int cpu_cgroup_can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
+				 struct cgroup_taskset *tset)
 {
+	struct task_struct *task;
+
+	cgroup_taskset_for_each(task, cgrp, tset) {
 #ifdef CONFIG_RT_GROUP_SCHED
-	if (!sched_rt_can_attach(cgroup_tg(cgrp), tsk))
-		return -EINVAL;
+		if (!sched_rt_can_attach(cgroup_tg(cgrp), task))
+			return -EINVAL;
 #else
-	/* We don't support RT-tasks being in separate groups */
-	if (tsk->sched_class != &fair_sched_class)
-		return -EINVAL;
+		/* We don't support RT-tasks being in separate groups */
+		if (task->sched_class != &fair_sched_class)
+			return -EINVAL;
 #endif
+	}
 	return 0;
 }
 
-static void
-cpu_cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
+static void cpu_cgroup_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
+			      struct cgroup_taskset *tset)
 {
-	sched_move_task(tsk);
+	struct task_struct *task;
+
+	cgroup_taskset_for_each(task, cgrp, tset)
+		sched_move_task(task);
 }
 
 static void
@@ -9480,8 +9487,8 @@ struct cgroup_subsys cpu_cgroup_subsys = {
 	.name		= "cpu",
 	.create		= cpu_cgroup_create,
 	.destroy	= cpu_cgroup_destroy,
-	.can_attach_task = cpu_cgroup_can_attach_task,
-	.attach_task	= cpu_cgroup_attach_task,
+	.can_attach	= cpu_cgroup_can_attach,
+	.attach		= cpu_cgroup_attach,
 	.exit		= cpu_cgroup_exit,
 	.populate	= cpu_cgroup_populate,
 	.subsys_id	= cpu_cgroup_subsys_id,