2016-10-28 14:52 GMT-07:00 Michael Ma <make0...@gmail.com>: > 2016-10-28 14:48 GMT-07:00 Stephen Hemminger <step...@networkplumber.org>: >> On Fri, 28 Oct 2016 14:45:07 -0700 >> Michael Ma <make0...@gmail.com> wrote: >> >>> 2016-10-28 14:38 GMT-07:00 Stephen Hemminger <step...@networkplumber.org>: >>> > On Fri, 28 Oct 2016 14:36:27 -0700 >>> > Michael Ma <make0...@gmail.com> wrote: >>> > >>> >> Hi - >>> >> >>> >> Currently IFB uses tasklet to process tx/rx on the interface that >>> >> forwarded the packet to IFB. My understanding on why we're doing this >>> >> is that since dev_queue_xmit() can be invoked in interrupt, we want to >>> >> defer the processing of original tx/rx in case ifb_xmit() is called >>> >> from interrupt. >>> > >>> > dev_queue_xmit is only called from interrupt if doing netconsole. >>>
In fact this doesn't seem to explain since if the original path is tx and the context is interrupt, IFB will call dev_queue_xmit as well so the context can be interrupt in that case. Then tasklet is still unnecessary. >>> OK - so the reason is that netif_receive_skb() can only be invoked >>> from softirq and we have to use tasklet in IFB to guarantee this. >>> >>> Then if the original path is rx, tasklet is unnecessary because >>> ifb_xmit() is invoked from netif_receive_skb() which is always in the >>> softirq context, right? >> >> The other reason is to avoid deep kernel callstacks
