We are debugging this issue that netconsole message triggers pegged softirq
(ksoftirqd taking 100% CPU for many seconds). We found this issue in
production with both bnxt and ixgbe, on a 4.11 based kernel. This is easily
reproducible with ixgbe on 4.11, and latest net/net-next (see [1] for more
detail).
After debugging for some time, we found that this issue is likely related
to 39e6c8208d7b ("net: solve a NAPI race"). After reverting this commit,
the steps described in [1] cannot reproduce the issue on ixgbe. Reverting
this commit also reduces the chances we hit the issue with bnxt (it still
happens with a lower rate).
I tried to fix this issue with relaxed variant (or older version) of
napi_schedule_prep() in netpoll, just like the one on napi_watchdog().
However, my tests do not always go as expected.
Please share your comments/suggestions on which direction shall we try
to fix this.
Thanks in advance!
Song
[1] https://www.spinics.net/lists/netdev/msg522328.html
