linux-kernel - [BUG] Interesting race between cpufreq_ondemand and snd

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Message-Id: <200706160233.47659.caglar@pardus.org.tr>
Date:	Sat, 16 Jun 2007 02:33:41 +0300
From:	"S.Çağlar Onur" <caglar@...dus.org.tr>
To:	linux-kernel@...r.kernel.org
Cc:	davej@...emonkey.org.uk, cpufreq@...ts.linux.org.uk, tiwai@...e.de
Subject: [BUG] Interesting race between cpufreq_ondemand and snd_atiixp

Hi;

One of our colleagues found following problem with his old laptop while 
testing Linus's latest git with external alsa-driver (v1.0.14). And we can 
also reproduce same problem with 2.6.18.8 so it seems not a new regression 
(if it is a regression).

As a summary "sound stops to work if cpufreq_ondemand governor is used" on 
that laptop. Problem occurs only if cpufreq_* modules are loaded and %100 
reproducable if system configured for ondemand governor. 

Here are the steps to reproduce the problem on that laptop;

1. Boot system with cpufreq_* modules blacklisted
   strace -o log -f -tttTTT mpg123 some.mp3

works without a problem [full log @ 1]

2. modprobe cpufreq_ondemand
   echo "ondemand" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
   strace -o log -f -tttTTT mpg123 some.mp3

hangs and no sound at all [full log @ 2]

3. echo "ondemand" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
   strace -o log -f -tttTTT mpg123 some.mp3

works without a problem [full log @ 3]
	
And with both 2.6.18.8 and 2.6.22-rc4 KDE (artsd) starts to gave "Operation 
not denied" errors on login, and after that error occured stracing mpg123 
from console gaves following output (the very same check of semctl fails with 
EINTR with second) [full log @ 4];
 
...
4004  1181948891.899907 semget(5678293, 1, IPC_CREAT|0660) = 1081344 
<0.000010>
4004  1181948891.899945 semctl(1081344, 0, IPC_64|IPC_STAT, 0xbfd1b498) = 0 
<0.000009>
4004  1181948891.899981 semctl(1081344, 0, IPC_64|IPC_SET, 0xbfd1b498) = -1 
EPERM (Operation not permitted) <0.000009>
4004  1181948891.900026 semop(1081344, 0xbfd1b6a0, 2) = -1 EINTR (Interrupted 
system call) <15.979441>
4004  1181948907.879574 --- SIGTERM (Terminated) @ 0 (0) ---
4004  1181948907.879782 +++ killed by SIGTERM +++

You can also find dmesg [5], lspci -vv [6], lsmod [7], /proc/cpuinfo 
[8], /proc/interrupts [9] and used .config [10] from there.

I have also a physical access to that laptop so please just ask if you want 
anything else.

[1] http://cekirdek.pardus.org.tr/~caglar/kernel/working
[2] http://cekirdek.pardus.org.tr/~caglar/kernel/notworking
[3] http://cekirdek.pardus.org.tr/~caglar/kernel/againworking
[4] http://cekirdek.pardus.org.tr/~caglar/kernel/perm
[5] http://cekirdek.pardus.org.tr/~caglar/kernel/dmesg_2.6.22
[6] http://cekirdek.pardus.org.tr/~caglar/kernel/lspci
[7] http://cekirdek.pardus.org.tr/~caglar/kernel/lsmod_2.6.22
[8] http://cekirdek.pardus.org.tr/~caglar/kernel/cpuinfo
[9] http://cekirdek.pardus.org.tr/~caglar/kernel/interrupts
[10] http://cekirdek.pardus.org.tr/~caglar/kernel/config

Cheers
-- 
S.Çağlar Onur <caglar@...dus.org.tr>
http://cekirdek.pardus.org.tr/~caglar/

Linux is like living in a teepee. No Windows, no Gates and an Apache in house!

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