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

From: Matthias Andree (matthias.andree@stud.uni-dortmund.de)
Date: Thu Dec 28 2000 - 08:53:37 EST


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 11 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
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
Please read the FAQ at http://www.tux.org/lkml/



This archive was generated by hypermail 2b29 : Sun Dec 31 2000 - 21:00:11 EST