Re: [PATCH] sched: fix another race when reading /proc/sched_debug

[Li Zefan <lizf@cn.fujitsu.com>]

Paul Menage wrote:
> On Tue, Dec 16, 2008 at 1:41 AM, Paul Menage <menage@google.com> wrote:
>> It should be OK to rcu-free cgrp and have it still safe to call
>> cgroup_path() on it - as long as we're confident that the dentry (and
>> all its parents) won't be released until after the RCU section as
>> well, since that's where we get the path elements from. And that does
>> seem to be the case from looking at dcache.c
>>
>> It's certainly nicer than having two calls to synchronize_rcu() in
>> quick succession in cgroup_diput().
> 
> How about something like this?
> 

This solves half of the problem..

This avoids accessing a destroyed cgroup, but still race with cgroup_create.
You sugguested call cgroup_create_dir() before calling subsystems' create()
method.

> Paul
> 
>  include/linux/cgroup.h |    9 +++++++++
>  kernel/cgroup.c        |   49 ++++++++++++++++++++++++++++---------------------
>  2 files changed, 37 insertions(+), 21 deletions(-)
>