Messages in this thread | | | Date | Sun, 17 Feb 2002 21:29:01 -0500 (EST) | From | Bill Davidsen <> | Subject | Re: [patch] sys_sync livelock fix |
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On Tue, 12 Feb 2002, Andrew Morton wrote:
> Thing is, at shutdown all the tasks which are generating write > traffic should have been killed off, and the filesystems unmounted > or set readonly. There's no obvious way in which this shutdown > sequence can be indefinitely stalled by the problem we're discussing here. > > If the shutdown scripts are calling sys_sync() *before* killing > everything then yes, the scripts could hang indefinitely. Is > this the case? > > If "yes" then the scripts are dumb. Just remove the `sync' call. > > If "no" then something else is causing the hang.
I recently had the Linux version of Cyclone (usenet transit server) get unhappy and start growing load without bounds. At L.A. 60 I issued a killall the the application (which ran on happily), then a killall (-9) which also didn't kill the processes (there is a problems there, a process shouldNOT keep running after ill -9!). There a "reboot" which hung, and finally a "reboot -n" which actually rebooted the machine.
Since -n only means "do sync but don't wait" I have to think that the problem is not that the script doesn't issue a kill, but that the kill doesn't work. I think making the sync(2) a single pass write of current dirty buffers is the only way to avoid stuff like this. making kill -9 work would be great too, there seems to be a long term problem with threaded programs which are hard to kill.
Just another data point, the bug in this case is not in shutdown.
-- bill davidsen <davidsen@tmr.com> CTO, TMR Associates, Inc Doing interesting things with little computers since 1979.
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