Messages in this thread | | | Date | Wed, 22 Feb 2012 02:04:34 +0100 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 2/2] cgroup: Walk task list under tasklist_lock in cgroup_enable_task_cg_list |
| |
On Tue, Feb 21, 2012 at 05:00:15PM -0800, Tejun Heo wrote: > On Wed, Feb 22, 2012 at 01:55:28AM +0100, Frederic Weisbecker wrote: > > > > + * We need tasklist_lock because RCU is not safe against > > > > + * while_each_thread(). Besides, a forking task that has passed > > > > + * cgroup_post_fork() without seeing use_task_css_set_links = 1 > > > > + * is not guaranteed to have its child immediately visible in the > > > > + * tasklist if we walk through it with RCU. > > > > + */ > > > > > > Maybe add TODO to remove the lock once do_each_thread()/while_each_thread() > > > is made rcu safe. On a large system, it could take a while to iterate > > > over every thread in the system. Thats a long time to hold a spinlock. > > > But it only happens once so probably not that big a deal. > > > > I think that even if while_each_thread() was RCU safe, that wouldn't > > work here. > > Guys, this is one time thing. It happens *once* after boot and we're > already holding exclusive lock. There's no reason to optimize this at > all. Let's just keep it simple.
For now I agree. But one day the real time guys might eye that thing.
| |