On Wed, May 23 2018 at 5:21am -0400, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > On Tue, May 22, 2018 at 02:52:54PM -0400, Mike Snitzer wrote: > > On Tue, May 22 2018 at 2:34am -0400, > > Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > > > > Please CC the author and maintainers of the swait code. > > > > > > My impression is that this is the wrong thing to do. The swait code > > > is supposed to be simple and self contained, and if you want to do > > > anything else use normal waitqueues. > > > > You said the same thing last time around. I've since cc'd Peter and > > Thomas and haven't heard back, see: > > https://www.redhat.com/archives/dm-devel/2018-May/msg00048.html > > Yeah, sorry, got lost :/ np > > The entire point of exporting these symbols is to allow use of the > > "simple waitqueue" code to optimize -- without resorting to using normal > > waitqueues. > > So I don't immediately object to exporting them; however I do share some > of hch's concerns. The reason swait exists is to be deterministic (for > RT) -- something that regular wait code cannot be. > > And by (ab)using / exporting the wait internal lock you risk loosing > that. So I don't think the proposed usage is bad, it is possible to > create badness. Understood. > So if we're going to export them; someone needs to keep an eye on things > and ensure the lock isn't abused. I'll update the patch header and swait.h to reflect these requirements and send out a new patch. If you could then reply with your explicit Ack I can stage it for 4.18 via linux-dm.git to ease cross tree dependencies (given dm-writecache depends on these exports) -- provided you're OK with me doing that. Thanks, Mike -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
