Re: [PATCH UPDATED 03/10] threadgroup: extend threadgroup_lock() to cover exit and exec

[Tejun Heo <tj@kernel.org>]

Hello again, Linus.

On Sun, Nov 27, 2011 at 01:25:58PM -0800, Tejun Heo wrote:
> The problem is that cred_guard_mutex uses _interruptible/_killable
> operations and rwsem doesn't have them, so cred_guard_mutex can't be
> easily replaced with write-locking group_rwsem.
> 
> If the two locks can't be merged, under the proposed scheme, while not
> exactly pretty, both fork/exit and exec paths go through single
> locking and only the ones which want stable threadgroup need to grab
> both locks, so IMHO it is at least reasonable.
> 
> Any better ideas?

I agree that the proposed solution is rather ugly but stable
thread-group is a valid mechanism to have and cgroup can benefit a lot
from it.  I'd be happy to revamp the implementation if anyone can come
up with a better way and can add big fat comment stating that.  Until
something better comes up, would it be okay to stick with this
implementation?

Thanks.

-- 
tejun