Re: bug in kernel 2.6.21-rc1-git1: conventional floppy drive cannotbe mounted without hanging up the whole system

From: Jiri Slaby
Date: Mon Feb 26 2007 - 10:12:05 EST


Jiri Slaby napsal(a):
Once again and for the last time: I do not state that floppy.c is broken. I only state that it is immpossible to mount a floppy drive with kernel 2.6.21-rc1-git1. Kernel 2.6.20 is OK. But 2.6.21-rc1-git1 is definitely buggy!
I did some work already:
a. I copied the following modules from the intact and sane kernel 2.6.20 into the 2.6.21-rc1-git1 tree:
cdrom.h, floppy.c, init.h, io.h, proc_misc.c, setup.c, timer.h, uaccess.h
b. I adjusted some hunks of the patch for module main.c (part of patch-2.6.21-rc1) to make the kernel compile without errors.
But the problem still persists, and I do not have any idea anymore where the offensive hunks in patch-2.6.21-rc1 could reside.

Questions:
a. Can someone please confirm the described problem?

Yup (last -mm).

Ok, this commit is the culprit:
Commit: 2ff2d3d74705d34ab71b21f54634fcf50d57bdd5
Author: Stephane Eranian <eranian@xxxxxxxxxx> Tue, 13 Feb 2007 13:26:22 +0100

[PATCH] i386: add idle notifier

Add a notifier mechanism to the low level idle loop. You can register a
callback function which gets invoked on entry and exit from the low level id
loop. The low level idle loop is defined as the polling loop, low-power cal
or the mwait instruction. Interrupts processed by the idle thread are not
considered part of the low level loop.

The notifier can be used to measure precisely how much is spent in useless
execution (or low power mode). The perfmon subsystem uses it to turn on/off
monitoring.

Signed-off-by: stephane eranian <eranian@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
Signed-off-by: Andi Kleen <ak@xxxxxxx>

---

Reverting (some manual work due to irq.c changes) this on latest -mm allows me to mount floppy again.

regards,
--
http://www.fi.muni.cz/~xslaby/ Jiri Slaby
faculty of informatics, masaryk university, brno, cz
e-mail: jirislaby gmail com, gpg pubkey fingerprint:
B674 9967 0407 CE62 ACC8 22A0 32CC 55C3 39D4 7A7E

Hnus <hnus@xxxxxxxxxx> is an alias for /dev/null
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