Hi Anssi, On Mon, Dec 3, 2018 at 4:02 PM Anssi Hannula <anssi.hann...@bitwise.fi> wrote: > > Hi, > > On 3.12.2018 6:52, Harini Katakam wrote: > > Hi Anssi, > > On Fri, Nov 30, 2018 at 11:53 PM Anssi Hannula <anssi.hann...@bitwise.fi> > > wrote: > >> Bit RX_USED set to 0 in the address field allows the controller to write > >> data to the receive buffer descriptor. > >> > >> The driver does not ensure the ctrl field is ready (cleared) when the > >> controller sees the RX_USED=0 written by the driver. The ctrl field might > >> only be cleared after the controller has already updated it according to > >> a newly received frame, causing the frame to be discarded in gem_rx() due > >> to unexpected ctrl field contents. > >> > >> A message is logged when the above scenario occurs: > >> > >> macb ff0b0000.ethernet eth0: not whole frame pointed by descriptor > >> > >> Fix the issue by ensuring that when the controller sees RX_USED=0 the > >> ctrl field is already cleared. > >> > >> This issue was observed on a ZynqMP based system. > >> > > Thanks for the patch. > > Could you please describe the test in which this behavior was observed? > > Sure. The testcase I used for the patches is: > > - RT_FULL kernel, > - CPU-bound SCHED_FF RT priority 15 process (with > rcutree.kthread_prio=20 to avoid RCU starvation), > - Pyropus memtester running for 3GB (system has 4GB memory), > - "ping -f -l 5000 -s 100" running from a PC. > > The "not whole frame pointed by descriptor" issue occurs within minutes > and the RX memory corruption within an hour. I did not try to reduce the > testcase to a minimum. > > Both were also observed using real production loads (that of course do > not have CPU-bound RT tasks). > > > Were you able to confirm that this was because of the ctrl field being > > cleared late? This error can also be observed under stress when RX UBR > > is observed. > > I observed that the issue occurred without this patch, and didn't occur > after applying this patch (individually), but I didn't check it further > than that. If you have anything you'd like me to test, let me know.
Thanks for the details. Regards, Harini
