Linux 2.2.18: /proc/apm slows system time (was: Linux 2.2.19pre3)

[Matthias Andree <matthias.andree@stud.uni-dortmund.de>]

On Thu, 28 Dec 2000, Alan Cox wrote:

> > CONFIG_APM_ALLOW_INTS. I'll investigate this right now and report back
> > what I find.
> 
> That would be interesting

Forget this all.

I found the problem trigger, it's reading from /proc/apm, for a reason I
cannot currently see.

Current config, as far as it's APM-related:
CONFIG_APM=y
# CONFIG_APM_IGNORE_USER_SUSPEND is not set
# CONFIG_APM_DO_ENABLE is not set
# CONFIG_APM_CPU_IDLE is not set
# CONFIG_APM_DISPLAY_BLANK is not set
CONFIG_APM_RTC_IS_GMT=y
CONFIG_APM_ALLOW_INTS=y
# CONFIG_APM_REAL_MODE_POWER_OFF is not set
# CONFIG_TOSHIBA is not set

I had found out that my clock was slow while dnetc was running. I had a
dummy loader that just did while(1) {} which did not slow my clock. Now, I
straced that dnetc beast and found out that it reads /proc/apm quite
often.

I can have my clock almost halt with this one:

while cat /proc/apm ; do : ; done

If I leave this running for 15 s, my system time drifts back 11½ s.


Relevant dmesg:
apm: BIOS version 1.2 Flags 0x03 (Driver version 1.13)


Board: Gigabyte 7ZXR, BIOS rev. F4 (VIA KT133 chip set, AMIBIOS).



I can and will test further, also with recompiled kernels, but I need
directions what to test.

-- 
Matthias Andree
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