On Sat, Jan 23, 2021 at 07:26:24PM -0800, Jakub Kicinski wrote: > On Fri, 22 Jan 2021 09:47:01 +0100 Lukas Wunner wrote: > > sch_handle_egress() returns either the skb or NULL to signal to its > > caller __dev_queue_xmit() whether a packet should continue to be > > processed. > > > > The skb is always non-NULL, otherwise __dev_queue_xmit() would hit a > > NULL pointer deref right at its top. > > > > But the compiler doesn't know that. So if sch_handle_egress() signals > > success by returning the skb, the "if (!skb) goto out;" statement > > results in a gratuitous NULL pointer check in the Assembler output. > > Which exact compiler are we talking about it? Did you report this? > As Eric pointed the compiler should be able to figure this out quite > easily. I tested with gcc 8, 9, 10. No need to report as it's the expected behavior with -fno-delete-null-pointer-checks, whose motivation appears questionable though (per my preceding e-mail). Thanks, Lukas
