On Wed 13-04-16 15:37:34, Tejun Heo wrote: > Hello, Michal. > > On Wed, Apr 13, 2016 at 09:23:14PM +0200, Michal Hocko wrote: > > I think we can live without lru_add_drain_all() in the migration path. > > We are talking about 4 pagevecs so 56 pages. The charge migration is > > Ah, nice. > > > racy anyway. What concerns me more is how all this is fragile. It sounds > > just too easy to add a dependency on per-cpu sync work later and > > reintroduce this issue which is quite hard to detect. > > Cannot we come up with something more robust? Or at least warn when we > > try to use per-cpu workers with problematic locks held? > > Yeah, workqueue does limited lockdep annotation but it doesn't > integrate fully with the rest of dependency tracking. It'd be nice to > have that. Don't know how to tho. I was thinking about something like flush_per_cpu_work() which would assert on group_threadgroup_rwsem held for write. But this still sounds suboptimal to me. Do we really have to do cgroup_threadgroup_change_begin for kworker threads? They are PF_NO_SETAFFINITY so they cannot be moved AFAIR. Or am I missing something? -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
