On Sun, 2017-06-04 at 21:23 -0500, Chien Tin Tung wrote: > Sun, Jun 04, 2017 at 08:36:35AM +0300, Leon Romanovsky wrote: > > > > On Fri, Jun 02, 2017 at 11:28:49AM -0500, Shiraz Saleem wrote: > > > > > > On Wed, May 31, 2017 at 02:10:31PM -0600, Bart Van Assche wrote: > > > > > > > > On Wed, 2017-05-31 at 12:42 -0500, Shiraz Saleem wrote: > > > > > > > > > > > > > > > > > 5. I proposed a solution -> go and fix your user space > > > > > > program. > > > > > > > > > > This is a kernel patch you are trying to revert, you are > > > > > breaking existing > > > > > kernel functionality. Nothing to do with user space. > > > > > > > > > > Bottom line, come up with a solution that will address both > > > > > port mapper > > > > > functionality and your issue. > > > > > > > > Hello Shiraz, > > > > > > > > Sorry that this means additional work for you, but I agree with > > > > Leon that > > > > user space software should not assume that netlink sockets are > > > > a reliable > > > > communication mechanism. > > > > > > Hi Bart - Thank you for your response. > > > > > > The original problem was that ibnl_unicast, which is used to send > > > nl messages from > > > portmapper kernel space to user-space, would occasionally and > > > momentarily fail under stress. > > > We could have retried the call for a certain amount of time, but > > > since netlink_unicast has a > > > nonblock/block parameter, we chose to use the blocking option > > > with a timeout. So we thought we > > > did account for deadlocks with this timeout. > > > > Not really, you just reduced the chances. In very large scale, you > > will > > have a very large chances of such deadlocks. > > Please stop using the word deadlock until you can prove that the > deadlock exists with the timeout > in place. He doesn't need to use the word deadlock for you to know that if you have a non-blocking function that is failing under load, and then you replace it with a blocking function but with a timeout, then it can also fail under load, and therefore you have not really solved the problem. -- Doug Ledford <dledford@xxxxxxxxxx> GPG KeyID: B826A3330E572FDD Key fingerprint = AE6B 1BDA 122B 23B4 265B 1274 B826 A333 0E57 2FDD -- 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
