• Tejun Heo's avatar
    memcg: relocate charge moving from ->attach to ->post_attach · 264a0ae1
    Tejun Heo authored
    Hello,
    
    So, this ended up a lot simpler than I originally expected.  I tested
    it lightly and it seems to work fine.  Petr, can you please test these
    two patches w/o the lru drain drop patch and see whether the problem
    is gone?
    
    Thanks.
    ------ 8< ------
    If charge moving is used, memcg performs relabeling of the affected
    pages from its ->attach callback which is called under both
    cgroup_threadgroup_rwsem and thus can't create new kthreads.  This is
    fragile as various operations may depend on workqueues making forward
    progress which relies on the ability to create new kthreads.
    
    There's no reason to perform charge moving from ->attach which is deep
    in the task migration path.  Move it to ->post_attach which is called
    after the actual migration is finished and cgroup_threadgroup_rwsem is
    dropped.
    
    * move_charge_struct->mm is added and ->can_attach is now responsible
      for pinning and recording the target mm.  mem_cgroup_clear_mc() is
      updated accordingly.  This also simplifies mem_cgroup_move_task().
    
    * mem_cgroup_move_task() is now called from ->post_attach instead of
      ->attach.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Acked-by: default avatarMichal Hocko <mhocko@kernel.org>
    Debugged-and-tested-by: default avatarPetr Mladek <pmladek@suse.com>
    Reported-by: default avatarCyril Hrubis <chrubis@suse.cz>
    Reported-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
    Fixes: 1ed13287 ("sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem")
    Cc: <stable@vger.kernel.org> # 4.4+
    264a0ae1
memcontrol.c 151 KB