Messages in this thread | | | From | Jeff Moyer <> | Date | Thu, 1 Jul 2004 13:53:16 -0400 | Subject | Re: netconsole hangs w/ alt-sysrq-t |
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==> Regarding Re: netconsole hangs w/ alt-sysrq-t; Matt Mackall <mpm@selenic.com> adds:
mpm> 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.
mpm> Is it because we're spinning for too long waiting for skbs or is it mpm> just because sysrq-t takes that long to dump its guts? How does the mpm> watchdog get tickled in the sysrq-t over slow serial console case?
mpm> In other words, would this better be done between dumps in the sysrq-t mpm> loop where we actually know we're making forward progress?
Good point. I tend to center my thinking too much around netdump. You're right, if we're waiting too long for skb's, we probably should trigger the NMI watchdog. It also appears that show_state includes a call to touch_nmi_watchdog in its loop.
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