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, 8 insertions, 5 deletions

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 0e8457da6f95..3b8e0edbe693 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7044,10 +7044,13 @@ static int __perf_cgroup_move(void *info)
         return 0;
 }
 
-static void
-perf_cgroup_attach_task(struct cgroup *cgrp, struct task_struct *task)
+static void perf_cgroup_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
+                               struct cgroup_taskset *tset)
 {
-        task_function_call(task, __perf_cgroup_move, task);
+        struct task_struct *task;
+
+        cgroup_taskset_for_each(task, cgrp, tset)
+                task_function_call(task, __perf_cgroup_move, task);
 }
 
 static void perf_cgroup_exit(struct cgroup_subsys *ss, struct cgroup *cgrp,
@@ -7061,7 +7064,7 @@ static void perf_cgroup_exit(struct cgroup_subsys *ss, struct cgroup *cgrp,
         if (!(task->flags & PF_EXITING))
                 return;
 
-        perf_cgroup_attach_task(cgrp, task);
+        task_function_call(task, __perf_cgroup_move, task);
 }
 
 struct cgroup_subsys perf_subsys = {
@@ -7070,6 +7073,6 @@ struct cgroup_subsys perf_subsys = {
         .create         = perf_cgroup_create,
         .destroy        = perf_cgroup_destroy,
         .exit           = perf_cgroup_exit,
-        .attach_task    = perf_cgroup_attach_task,
+        .attach         = perf_cgroup_attach,
 };
 #endif /* CONFIG_CGROUP_PERF */