em driver regression

[Mikolaj Golub]

On Sun, 11 Apr 2010 23:40:03 +0300 Mikolaj Golub wrote:

 MG> Hi,

 MG> Today I have upgraded the kernel in my VirtualBox (3.1.51.r27187) to the
 MG> latest current and have "em0: Watchdog timeout -- resetting" issue. My
 MG> previous kernel was for Mar 12.

 MG> Tracking the revision where the problem appeared I see that the issue is not
 MG> observed for r203834 and starts to observe after r205869.

 MG> Interestingly, if I enter ddb and then exit (sometimes I needed to do this
 MG> twice) the errors stop and network starts working.

Adding some prints I observed the following:

Apr 14 07:14:08 hasta kernel: em0: lem_init_locked started (ticks 813, watchdog_time: 0)
Apr 14 07:14:08 hasta kernel: em0: lem_init_locked returned at 3 (ticks 818, watchdog_time: 0)
Apr 14 07:14:08 hasta kernel: em0: setting watchdog_check to TRUE in lem_mq_start_locked 1 (ticks 818, watchdog_
time: 0)
Apr 14 07:14:08 hasta kernel: em0: lem_init_locked started (ticks 818, watchdog_time: 0)
Apr 14 07:14:08 hasta kernel: em0: lem_init_locked returned at 3 (ticks 823, watchdog_time: 0)
Apr 14 07:14:08 hasta kernel: em0: setting watchdog_check to TRUE in lem_mq_start_locked 1 (ticks 828, watchdog_
time: 0)
Apr 14 07:14:08 hasta kernel: em0: lem_txeof started (ticks: 923, watchdog_time: 0)
Apr 14 07:14:08 hasta kernel: em0: lem_txeof returned at 3 (ticks: 923, watchdog_time: 0)
Apr 14 07:14:08 hasta kernel: em0: lem_txeof started (ticks: 1023, watchdog_time: 0)
Apr 14 07:14:08 hasta kernel: em0: lem_txeof returned at 3 (ticks: 1023, watchdog_time: 0)
Apr 14 07:14:08 hasta kernel: em0: Watchdog timeout -- resetting (ticks: 1023, watchdog_time: 0)
Apr 14 07:14:08 hasta kernel: em0: lem_init_locked started (ticks 1024, watchdog_time: 0)
Apr 14 07:14:08 hasta kernel: em0: lem_init_locked returned at 3 (ticks 1028, watchdog_time: 0)
Apr 14 07:14:08 hasta kernel: em0: lem_txeof started (ticks: 1128, watchdog_time: 0)
Apr 14 07:14:08 hasta kernel: em0: lem_txeof returned at 1 (ticks: 1128, watchdog_time: 0)
Apr 14 07:14:08 hasta kernel: em0: Watchdog timeout -- resetting (ticks: 1128, watchdog_time: 0)
...

So althogh adapter->watchdog_check was set TRUE, adapter->watchdog_time was
never set.

I see that before r205869 watchdog_time was set in em_xmit but lem_xmit does
not contain this. After adding back this line to lem_xmit (see the first patch
below) the problem has gone on my box.

Also seeing that in the current em_mq_start_locked() both watchdog_check and
watchdog_time are set I tried another patch adding watchdog_time setting in
lem_mq_start_locked() too (see the second patch below). This has also fixed
the issue for me but I don't know if this is a correct fix and if this is the
only place where watchdog_time should be set (there are other places in the
function and in the code where watchdog_check is set to TRUE but watchdog_time
is not set).

-- 
Mikolaj Golub

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