When testing the myri10ge driver with 2.6.24-rc1, I found
that the machine crashed under heavy load:
Unable to handle kernel paging request at 0000000000100108 RIP:
[<ffffffff803cc8dd>] net_rx_action+0x11b/0x184
The address corresponds to the list_move_tail() in
netif_rx_complete():
if (unlikely(work == weight))
list_move_tail(&n->poll_list, list);
Eventually, I traced the crashes to calling netif_rx_complete() with
work_done == budget. From looking at other drivers, it appears that
one should only call netif_rx_complete() when work_done < budget.
To fix it, I changed the test in myri10ge_poll() so that it refers
to to work_done rather than looking at the rx ring status. If
work_done is < budget, then that implies we have no more packets to
process. Any races will be resolved by the NIC when the write to
irq_claim is made.
In myri10ge_clean_rx_done(), if we ever exceeded our budget, it would
report a work_done one larger than was acutally done. This is because
the increment was done in the conditional, so work_done would be
incremented regardless of whether or not the test passed or failed.
This would lead to the WARN_ON_ONCE(work > weight); warning in
net_rx_action triggering. I've moved the increment of work_done
inside the loop. Note that this would only be a problem when we had
exceeded our budget.
Signed off by: Andrew Gallatin <gallatin@myri.com>
Andrew Gallatin Myricom Inc
Signed-off-by: Jeff Garzik <jeff@garzik.org>
c956a24018