>>>>>>On Tue, 10 May 2005 17:27:01 +0200, Francois Wellenreiter
>>>>>><Francois.Wellenreiter@xxxxxxxx> said:
>
>
> Francois> - timeouts when exiting from KDB will never occur I have
> Francois> noticed that after a long time in KDB, some drivers enter
> Francois> in timeout sequences. Now, the different ITC values are
> Francois> saved when entering KDB and restored when going out.
>
> This sounds fragile to me. For one thing, the kernel may not use ITC
> at all for timeouts (true for most NUMA platforms). Also, even if the
> ITC is in use, you'd probably have to resync them on the slave CPUs
> after restoring the time-keeper's ITC value. Not to mention that if
> the timeout is related to an external event, then faking time won't
> help no matter what.
>
> --david
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David,
I agree that ITC management may be a bit risky and overall is
platform-dependent, but in my opinion, that was a better way than saving and
restoring global xtime variable which can be modified by only one CPU
(the main danger in such a case may occur when this CPU is working
when the other ones are already running KDB).
The time-outs that I have noticed dealt with journalled filesystem messages
(and sometimes lead to an unrecoverable machine crash),
that is the reason why I have implemented this feature. On the different
NUMA machines that I have tested, this problem did not appear again.
If you have some implementation ideas, they are really welcome.
Regards,
Francois
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