Re: netconsole hangs w/ alt-sysrq-t

[Matt Mackall <mpm@selenic.com>]

On Thu, Jul 01, 2004 at 12:54:50PM -0400, Jeff Moyer wrote:
> ==> Regarding Re: netconsole hangs w/ alt-sysrq-t; Matt Mackall <mpm@selenic.com> adds:
> 
> mpm> On Mon, Jun 28, 2004 at 12:58:22PM -0400, Jeff Moyer wrote:
> >> ==> Regarding Re: netconsole hangs w/ alt-sysrq-t; Matt Mackall
> >> <mpm@selenic.com> adds:
> mpm> No, I think we get to this on the non-NAPI route as well. The ->poll
> mpm> check keeps us from filtering twice.
> >> I'll have to take your word for it on this one, as I can't find a way
> >> into this code for the non-napi case.  Would anyone care to give an
> >> authoritative answer on this?
> 
> mpm> I could be mistaken, but that's my recollection from last summer.
> mpm> Hopefully I'll have some spare cycles for this next week.
>  
> >> One other thing we might consider is adding a call to
> >> touch_nmi_watchdog() to zap_completion_queue.
> 
> mpm> Not sure how I feel about that yet. If we can't get out of the guts of
> mpm> netpoll in a timely fashion, then perhaps that's an indication that
> mpm> the watchdog should indeed fire. Describe the scenario where you think
> mpm> we should do this, please.
> 
> Alt-Sysrq-t from the keyboard on a heavily-loaded UP system.

Is it because we're spinning for too long waiting for skbs or is it
just because sysrq-t takes that long to dump its guts? How does the
watchdog get tickled in the sysrq-t over slow serial console case?

In other words, would this better be done between dumps in the sysrq-t
loop where we actually know we're making forward progress?

-- 
Mathematics is the supreme nostalgia of our time.