]> git.karo-electronics.de Git - linux-beck.git/commit
sched/cgroup: Fix cpu_cgroup_fork() handling
authorVincent Guittot <vincent.guittot@linaro.org>
Fri, 17 Jun 2016 11:38:55 +0000 (13:38 +0200)
committerIngo Molnar <mingo@kernel.org>
Mon, 27 Jun 2016 10:17:52 +0000 (12:17 +0200)
commitea86cb4b7621e1298a37197005bf0abcc86348d4
treef73641b3f3ceddb0ea71e71611a27af0f23f908d
parent010114739d294c474764c94196d32fb92e233657
sched/cgroup: Fix cpu_cgroup_fork() handling

A new fair task is detached and attached from/to task_group with:

  cgroup_post_fork()
    ss->fork(child) := cpu_cgroup_fork()
      sched_move_task()
        task_move_group_fair()

Which is wrong, because at this point in fork() the task isn't fully
initialized and it cannot 'move' to another group, because its not
attached to any group as yet.

In fact, cpu_cgroup_fork() needs a small part of sched_move_task() so we
can just call this small part directly instead sched_move_task(). And
the task doesn't really migrate because it is not yet attached so we
need the following sequence:

  do_fork()
    sched_fork()
      __set_task_cpu()

    cgroup_post_fork()
      set_task_rq() # set task group and runqueue

    wake_up_new_task()
      select_task_rq() can select a new cpu
      __set_task_cpu
      post_init_entity_util_avg
        attach_task_cfs_rq()
      activate_task
        enqueue_task

This patch makes that happen.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
[ Added TASK_SET_GROUP to set depth properly. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
kernel/sched/core.c
kernel/sched/fair.c
kernel/sched/sched.h