Re: gettimeofday problem

Gabriel Paubert
2002-06-26T10:58:11Z

Chris Friesen wrote:

> "Richard B. Johnson" wrote:
>
>
>>This has been running since I first read your mail about 10:00 this
>>morning. The kernel is 2.4.18
>>
>
>
>
> Using that code, I can reliably trigger the fault on 2.2.17 on a G4 desktop,
> while it doesn't trigger on 2.4.18 on a G4 cPCI blade.

Given the fact that the relevant code has been almost completely rewritten
for 2.4 (I'm the culprit), this is not surprising.

The rewrite was mostly to make the code more robust in case of missed
ticks: all PPC are now guaranteed to withstand at least (HZ-1) lost clock
interrupts before things go awfully wrong (this was very useful when the
frame buffer drivers blocked interrupts for too long during screen
switching). There are also several other less visible bug fixes: when
connected to an NTP server, in some cases the timebase frequency appeared
to vary depending on system load (fixed by a different algorithm to
compute values to load into the decrementer) and other bogosities.

Now if you are able to trigger a problem with 2.4. I'm extremely interested.

>
> I saw this a long time back (a year or two) on 2.2 but never really tracked it
> down properly as it wasn't a showstopper and I had other things to do at the
> time.

I have a patch for 2.2, but it is mixed up in a set of huge patches for
Motorola VME boards (MVME2600 and 2400 series) with a bootloader
(including an x86 emulator to initialize graphics boards by executing the
BIOS ROM), VME drivers and other things that you can find at:

ftp://vlab1.iram.es/pub/linux-2.2

I could extract the timing patches if somebody is interested, but not in
the next few days (I have patches which apply to more recent versions than
the ones I put on the FTP area).

Gabriel.