[maemo-developers] Continuous reboot problem with the N770 hacker edition

From: Eero Tamminen eero.tamminen at nokia.com
Date: Thu Apr 26 18:56:40 EEST 2007

ext Frantisek Dufka wrote:
>> That shouldn't happen. 
> Happened to me with N770 and IT2006. Just one solid hangup while web
> browsing, watchdog reboot and I had infinite reboot loop.

Well, I was talking more about the latest N800 release than something
for N770.

> Also I have lost some gconf preferences more times when device rebooted
> randomly. Missing preference may cause crash for some system application
> that expects some setting to be always present.

Things "should" have reasonable defaults (and actually test that
they work without them).

>> JFFS2 keeps the internal filesystem in
>> consistent state although the filesystem hadn't be properly
>> unmounted (unlike the VFAT on MMC cards). 
> Yes that is not a problem.
>> Some individual files
>> could get only partially written, but all applications should
>> be doing such writes safely (write to temp file and rename once
>> writing is finished).
> This is the problem. It is not common at all to write to files in such
> way. In case you want to apppend some data to existing file it is not
> optimal to create new temporary file, copy all data and add few bytes.
> You seriously can't expect people writing code in such way.

For logs etc. you can of course append, I meant files which application
loads when it starts and where it matters what their contents are.

> I still think this watchdog thing is another legacy we have from Nokia
> as a phone company. It makes perfect sense for dumb phone. It makes less
>   sense for computer. Yes when device locks up you need a way to reset
> it. That is why you have reset button on computer and also reset hole on
> every PDA. I know it is internet tablet not computer or PDA but also
> Nokia should know that *this is not a phone* ;-)
> With reset hole one can reset device when (s)he wants. Watchdog may not
> make things worse when device locks up solid (i.e. kernel bug or
> feature) but rebooting device when some process dies of when things take
> too long can make more damage than benefit. I know this is hard to
> detect so my solution is to provide reset hole and do not try to guess.
> User probably can notice this situation and act accordingly.

This is improved a bit in latest release.  Most things are restartable
and device is rebooted only if restarting them fails too many times in
a row (Desktop, window manager etc).

However, without X server or D-BUS you cannot use the device at all
and all your UI processes exit automatically, so it doesn't make sense
to try to "keep the device up" if those exit/crash.

	- Eero

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