Bug 244187 - hald slows down system clock on systems with apm
Summary: hald slows down system clock on systems with apm
Keywords:
Status: CLOSED NOTABUG
Alias: None
Product: Fedora
Classification: Fedora
Component: hal
Version: 7
Hardware: All
OS: Linux
low
low
Target Milestone: ---
Assignee: David Zeuthen
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2007-06-14 13:14 UTC by nvwarr
Modified: 2013-03-06 03:51 UTC (History)
2 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed: 2008-05-30 11:30:57 UTC
Type: ---
Embargoed:


Attachments (Terms of Use)

Description nvwarr 2007-06-14 13:14:37 UTC
Description of problem:
hald reads /proc/apm every 2 seconds, which causes the system clock to slow down.

Version-Release number of selected component (if applicable):
hal-0.5.9-8.fc7

How reproducible:
Always

Steps to Reproduce:
1. Stop hald.
2. System clock runs normally.
3. Restart hald.
4. System clock runs slow.
  
Actual results:
Hald slows down the system clock to such an extent and with such a large jitter
that ntp is no longer able to keep the system time synchronized, resulting in
massive clock drifts (i.e. hours). On my system, the slowdown was about 10 hours
per week.

Expected results:
Hald shouldn't slow down the system clock.

Additional info:
Actually, this is really a kernel bug, because any user can cat /proc/apm, which
has the same effect. I have filed a bug report against the kernel package too
(see https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=244177). However, this
is not a new bug in the kernel and when it was reported against kernel 2.2.18
over six years ago, the thread ended with Erik Mouw suggesting caching the
results of /proc/apm and Alan Cox saying this is a userspace issue:
http://www.ussg.iu.edu/hypermail/linux/kernel/0012.3/0669.html

In other words, unless the kernel people can fix the problem with /proc/apm,
userspace programs shouldn't read /proc/apm that frequently.

Commenting out lines 391 and 392 in hald/linux/apm.c (i.e. so read_from_apm is
no longer called) works around the problem.

Comment 1 Bug Zapper 2008-05-14 13:04:46 UTC
This message is a reminder that Fedora 7 is nearing the end of life. Approximately 30 (thirty) days from now Fedora will stop maintaining and issuing updates for Fedora 7. It is Fedora's policy to close all bug reports from releases that are no longer maintained. At that time this bug will be closed as WONTFIX if it remains open with a Fedora 'version' of '7'.

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Comment 2 Richard Hughes 2008-05-30 11:30:57 UTC
We need /proc/apm for the battery and AC detection. It sounds like a kernel bug
that needs fixing, not HAL. Sorry.


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