Messages in this thread | | | Date | Wed, 12 Oct 2011 20:29:05 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 3/4] threadgroup: extend threadgroup_lock() to cover exit and exec |
| |
On 10/12, Ben Blum wrote: > > On Wed, Oct 12, 2011 at 07:51:04PM +0200, Oleg Nesterov wrote: > > > > > Also, it makes the mechanism unnecessarily cgroup-specific without > > > gaining much if anything. > > > > Yes! And _personally_ I think it should be cgroup-specific, that is > > why I dislike the very fact do_exit() uses it directly. To me it would > > be cleaner to shift it into cgroup hooks. Yes, sure, this is subjective. > > In the fork path, threadgroup_fork_read_...() is also called directly, > not through cgroups. Would that change too?
Well, if you ask me, I'd prefer to move lock/unlock into cgroup_fork/cgroup_post_fork ;) Although the error path plays with it too. But this is minor.
> > In fact I still hope we can kill this sem altogether, but so far I have > > no idea how we can do this. We do need the new per-process lock to > > protect (in particular) ->thread_group. It is quite possible that it > > should be rw_semaphore. But in this case we down_write(), not _read > > in exit/fork paths, and its scope should be small. > > I'm confused - taking a big rwsem for writing in the fork/exit paths?
Yes, we need the new lock to avoid tasklist_lock.
> The point here is that even though fork/exit modify thread_group, they > are logical "readers"
Yes I see. And this is one of the reasons why we can't use this lock for above.
Oleg.
| |