On Thu, 10 Jul 2014, Sasha Levin wrote: > On 07/10/2014 02:52 PM, Hugh Dickins wrote: > > On Thu, 10 Jul 2014, Sasha Levin wrote: > >> > On 07/10/2014 01:55 PM, Hugh Dickins wrote: > >>>> > >> And finally, (not) holding the i_mmap_mutex: > >>> > > I don't understand what prompts you to show this particular task. > >>> > > I imagine the dump shows lots of other tasks which are waiting to get an > >>> > > i_mmap_mutex, and quite a lot of other tasks which are neither waiting > >>> > > for nor holding an i_mmap_mutex. > >>> > > > >>> > > Why are you showing this one in particular? Because it looks like the > >>> > > one you fingered yesterday? But I didn't see a good reason to finger > >>> > > that one either. > >> > > >> > There are a few more tasks like this one, my criteria was tasks that lockdep > >> > claims were holding i_mmap_mutex, but are actually not. > > You and Vlastimil enlightened me yesterday that lockdep shows tasks as > > holding i_mmap_mutex when they are actually waiting to get i_mmap_mutex. > > Hundreds of those in yesterday's log, hundreds of them in today's. > > What if we move lockdep's acquisition point to after it actually got the > lock? > > We'd miss deadlocks, but we don't care about them right now. Anyways, doesn't > lockdep have anything built in to allow us to separate between locks which > we attempt to acquire and locks that are actually acquired? > > (cc PeterZ) > > We can treat locks that are in the process of being acquired the same as > acquired locks to avoid races, but when we print something out it would > be nice to have annotation of the read state of the lock. I certainly hope someone can work on improving that. I imagine it would be easy, and well worth doing. But won't be looking into it myself. Hugh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>