On Thursday 19 July 2007 18:07, Ingo Molnar wrote:
> because i dont seem to be able to trigger Olaf's WARN_ON(), can you see
> anything in the ethtool output that i sent in the previous mail(s)?
If the WARN_ON doesn't trigger, I cannot see how my patch would affect
your system.
- IF we enter the if() branch in poll_napi, then the following
must hold:
- an interrupt from the e1000 arrived
- e1000_intr disables interrupts, increments irq_sem
(which is now 1) and schedules rx_action
- Now, inside poll_napi, the following happens:
- poll_napi is called, finds the device is marked for
polling, invokes dev->poll
- dev->poll calls netif_rx_complete (which does *not*
remove the device from the poll list), and re-enables
interrupts. irq_sem is now 0.
- Finally, the rx_action softirq is run, which calls dev->poll
again, which ends up invoking netif_rx_complete once more,
and tries to re-enable interrupts. The latter doesn't do
anything except decrementing irq_sem once more, which now
goes negative.
Which would trigger the WARN_ON.
Now, as you say the WARN_ON is never triggered, it follows that
we never end up in the if() branch of poll_napi. But that is
where the only substantial modification of my patch is.
Here's a somewhat drastic modification that should not change any
timing, but just verifies whether my patch is to blame at all. Can
you give it a try?
Thanks,
Olaf
--
Olaf Kirch | --- o --- Nous sommes du soleil we love when we play
[EMAIL PROTECTED] | / | \ sol.dhoop.naytheet.ah kin.ir.samse.qurax
---
Test patch
---
include/linux/netdevice.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Index: build-2.6/include/linux/netdevice.h
===================================================================
--- build-2.6.orig/include/linux/netdevice.h
+++ build-2.6/include/linux/netdevice.h
@@ -1027,7 +1027,7 @@ static inline void netif_rx_complete(str
* But at least it doesn't penalize the non-netpoll
* code path. */
if (test_bit(__LINK_STATE_POLL_LIST_FROZEN, &dev->state))
- return;
+ BUG();
#endif
local_irq_save(flags);
-
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