Subject: Re: console lost to Ctrl+Alt+F$n in 2.6.0-test5
From: Pat LaVarre <p.lavarre@ieee.org>
To: mpm@selenic.com
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <20030912230637.GB4489@waste.org>
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	 <1063390768.2898.15.camel@patehci2>  <20030912230637.GB4489@waste.org>
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Date: 12 Sep 2003 18:49:08 -0600
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> I'm working on this, it's rather messy. Your lockup might be caused by
> printk spew during console switch, see if it still locks up with the
> sleep debugging turned off.

Yes, thank you, Ctrl+Alt+F$n now works if only I
CONFIG_DEBUG_SPINLOCK_SLEEP=n.

Also `sudo cat /proc/kmsg | tee ...` also suddenly starts working.

I wonder if somehow /proc/kmsg now working is a clue?  Back with =y, my
`dmesg` was clean but via /proc/kmsg I was seeing garbage like

mmae t itbl

or:

mmae t itle

for what now again is such reassuring chatter as:

<6>scsi2 : SCSI emulation for USB Mass Storage devices
<5>  Vendor: Iomega    Model: RRD               Rev: 23.D
<5>  Type:   CD-ROM                             ANSI SCSI revision: 02
<7>WARNING: USB Mass Storage data integrity not assured
<7>USB Mass Storage device found at 3
<4>sr1: scsi3-mmc drive: 125x/125x caddy
<4>sr1: scsi3-mmc maybe not writeable
<4>sr1: scsi3-mmc writable profile: 0x0002
<7>Attached scsi CD-ROM sr1 at scsi2, channel 0, id 0, lun 0

Pat LaVarre

P.S. I could easily check to see if =y kills an ssh session or just the
display, if that helps.

P.P.S.

Tentatively I conclude "sleep debugging ... off" meant this .config
change because I see:

$ make defconfig
...
$ grep -i sleep .config
CONFIG_ACPI_SLEEP=y
CONFIG_ACPI_SLEEP_PROC_FS=y
CONFIG_DEBUG_SPINLOCK_SLEEP=y
$ vi +/DEBUG_SPINLOCK_SLEEP .config
...
Kernel hacking ...

Sleep-inside-spinlock checking (DEBUG_SPINLOCK_SLEEP)

If you say Y here, various routines which may sleep will become very
noisy if they are called with a spinlock held.
...

Google isn't quickly confirming/ denying this tentative conclusion of
mine.


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