Messages in this thread | | | Date | Sat, 9 Mar 2013 07:10:37 +0000 | From | Eric Wong <> | Subject | Re: epoll: possible bug from wakeup_source activation |
| |
Arve Hjønnevåg <arve@android.com> wrote: > On Fri, Mar 8, 2013 at 12:49 PM, Eric Wong <normalperson@yhbt.net> wrote: > > What happens if ep_modify calls ep_destroy_wakeup_source > > while __pm_stay_awake is running on the same epi->ws? > > Yes, that looks like a problem. I think calling > ep_destroy_wakeup_source with ep->lock held should fix that. It is not > clear how useful changing EPOLLWAKEUP in ep_modify is, so > alternatively we could remove that feature and instead only allow it > to be set in ep_insert.
ep->lock would work, but ep->lock is already a source of heavy contention in my multithreaded+epoll webservers.
Perhaps RCU can be used? I've no experience with RCU, but I've been meaning to get acquainted with RCU.
Another possible solution is to only use ep->ws and add an atomic counter to ep; so __pm_relax(ep->ws) is only called when the atomic counter reaches zero. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |