On Tue, Feb 28, 2017 at 04:47:05PM -0500, Doug Ledford wrote: > > I don't think that we should introduce an asych context into libibverbs. > > Why not? Generally, I dislike the idea of running threads from libraries, particularly libraries like ibverbs. So many apps get no benefit from the thread, but it sits there connected to udev.. But aside from that, threads create races, and in this case if the hidden thread has to run to get the up to date device list, then the application has to synchronize with it to get the up to date information. This is practically problematic because one of the areas we need to fix is rdma-cm which is already getting a kind of new-device notification from kernel messages that are not synchronized with udev or any other thread. In this case I think the simple solution is the most correct one - run readdir on every call to ibv_get_devices and do set-interesection with the internal list before returning the result. Easy, simple locking, no races to worry about. We probably also need to add some retries for opening /dev/uverbsXX based on sysfs to really solve all the races... Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
