Re: [PATCH 1/3] cgroup: simplify double-check locking in cgroup_attach_proc

[Li Zefan <lizf-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>]

Mandeep Singh Baines wrote:
> To keep the complexity of the double-check locking in one place,
> I moved the thread_group_leader check up into attach_task_by_pid.
> This allows us to use a goto instead of returning -EAGAIN.
> 
> While at it, converted a couple of returns to gotos and used
> rcu for the !pid case also in order to simplify the logic.
> 
> Changes in V2:
> * https://lkml.org/lkml/2011/12/22/86 (Tejun Heo)
>   * Use a goto instead of returning -EAGAIN
> 
> Signed-off-by: Mandeep Singh Baines <msb-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>

Acked-by: Li Zefan <lizf-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>

> Cc: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> Cc: Li Zefan <lizf-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
> Cc: Frederic Weisbecker <fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Cc: containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
> Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
> Cc: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Cc: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
> Cc: Paul Menage <paul-inf54ven1CmVyaH7bEyXVA@public.gmane.org>
> ---
>  kernel/cgroup.c |   79 ++++++++++++++++++++----------------------------------
>  1 files changed, 29 insertions(+), 50 deletions(-)