Hi Jan, On 03/05/2015 03:27 PM, Jan Kara wrote: > Hello, > > so after a long pause I've got back to my simplification patches around > get_user_pages(). After the simplification done by commit f035eb4e976ef5 > (videobuf2: fix lockdep warning) it seems unnecessary to take mmap_sem > already when calling __qbuf_userptr(). As far as I understand what > __qbuf_userptr() does, the only thing where mmap_sem is needed is for > get_userptr and possibly put_userptr memops. So it should be possible to > push mmap_sem locking down into these memops, shouldn't it? Or am I missing > something in __qbuf_userptr() for which mmap_sem is also necessary? No, you are correct. The mmap_sem can be pushed down, either to __qbuf_userptr or all the way to the videobuf2-dma/vmalloc get/put_userptr ops. > If I'm right, I can prepare patches to do that (and then on top of those > rebase patches which will make v4l2 core use some mm helper functions so > they don't have to care about details of mm locking, vmas, etc.). That would be really nice. Regards, Hans -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
