call for bge(4) testers

Gleb Smirnoff glebius at
Wed Aug 23 10:04:36 UTC 2006

On Wed, Aug 23, 2006 at 06:55:04PM +0900, Pyun YongHyeon wrote:
P> On Wed, Aug 23, 2006 at 01:37:41PM +0400, Gleb Smirnoff wrote:
P>  > On Tue, Aug 22, 2006 at 01:20:23PM +0900, Pyun YongHyeon wrote:
P>  > P> After fixing em(4) watchdog bug, I looked over bge(4) and I think
P>  > P> bge(4) may suffer from the same issue. So if you have seen occasional
P>  > P> watchdog timeout errors on bge(4) please give the attached patch a try.
P>  > P> The patch does fix false watchdog timeout error only.
P>  > P> Typical pheonoma for false watchdog timeout error are
P>  > P>        o polling(4) fix the issue
P>  > P>        o random watchdog error
P>  > P> 
P>  > P> If my patch fix the issue you could see the following messages.
P>  > P> "missing Tx completion interrupt!" or "link lost -- resetting"
P>  > 
P>  > I still think that this fix is incorrect. It is just a more gentle
P>  > recovery from a fake watchdog timeout.
P> Its sole purpose is to reinitialize hardware for real watchdog
P> timeouts. It's not fix for general watchdog timeouts. As I said other
P> mails, the fake watchdog timeout(losing Tx interrupts) for hardwares
P> with Tx interrupt moderation capability could be normal thing. So I
P> just want to know bge(4) also has the same feature(bug).

According to several emails about em(4) fake watchdog timeouts, the
problem can be fixed by setting debug.mpsafenet=0. This makes me think
that the problem isn't caused by TX interrupt moderation, but some race
in the kernel. Really, if_slowtimo() doesn't acquire driver lock before
checking and modifying the if_timer field.

Afaik, NIC drivers that can do interrupt moderation should set a timer
to a sane value, based on interrupt moderation settings, so that the
watchdog won't be ever called fakely.

P>  > The more I think, the more I doubt that we really need the
P>  > watchdog infrastructure that comes from old days.
P> Would you give other way to recover from Tx stuck condition without
P> using watchdog?

May be driver should take care of that theirselves, why not? At least
the callout routine will have access to the driver mutex, contrary to

Totus tuus, Glebius.

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