em net (optical GigE) driver hangs?

[John Polstra]

In article <FE045D4D9F7AED4CBFF1B3B813C8533701918A83 at mail.sandvine.com>,
Dave Dolson  <ddolson at sandvine.com> wrote:
> 
> Has anyone experienced em interface hangs after approx several days of heavy
> operation?
> 
> We are using a system which is mostly RELENG_4_7, using multiple optical em
> GigE devices.
> 
> The symptom is that the interface stops transmitting or receiving, reporting
> drops on output (no tx descriptors) and input errors (MPC stat-->no receive
> descriptors).
> 
> It turns out that all but 64 transmit descriptors are in use.  The driver is
> waiting for the "done" flag to be set so it can clean the descriptors.
> The device is also in the OACTIVE state at this time.
> 
> After the interface is brought down (or unplugged), the em watchdog timer
> goes off 5s later.
> 
> We are trying to figure out two things:
> 1. why did the driver lock up?
> 2. why didn't the watchdog timer go off earlier?
> 
> I think we would be happy to solve #2 given the rarity of the event.
> Is the RELENG_4 version likely to fix the problem?

I think the RELENG_4 version is likely to eliminate the problem.  See
the comment near the define of EM_RDTR in if_em.h (in the RELENG_4
version of that file, of course).

John
-- 
  John Polstra
  John D. Polstra & Co., Inc.                        Seattle, Washington USA
  "Disappointment is a good sign of basic intelligence."  -- Chögyam Trungpa