Re: [PATCH 2/3] don't take cgroup_mutex in destroy()

Tejun Heo wrote:

On Thu, Apr 19, 2012 at 07:49:17PM -0300, Glauber Costa wrote:

quoted

Most of the destroy functions are only doing very simple things
like freeing memory.

The ones who goes through lists and such, already use its own
locking for those.

* The cgroup itself won't go away until we free it, (after destroy)
* The parent won't go away because we hold a reference count
* There are no more tasks in the cgroup, and the cgroup is declared
  dead (cgroup_is_removed() == true)

For the blk-cgroup and the cpusets, I got the impression that the mutex
is still necessary.

For those, I grabbed it from within the destroy function itself.

If the maintainer for those subsystems consider it safe to remove
it, we can discuss it separately.

I really don't like cgroup_lock() usage spreading more.  It's
something which should be contained in cgroup.c proper.  I looked at
the existing users a while ago and they seemed to be compensating
deficencies in API, so, if at all possible, let's not spread the
disease.

Agreed. I used to do cleanups to remove cgroup_lock()s in subsystems
which are really not necessary.