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Date:      Fri, 23 Jul 1999 12:45:28 +0900
From:      Kazutaka YOKOTA <yokota@zodiac.mech.utsunomiya-u.ac.jp>
To:        "Richard A. Scheper" <scheper@toad.net>
Cc:        freebsd-smp@freebsd.org, yokota@zodiac.mech.utsunomiya-u.ac.jp
Subject:   Re: SMP + XDM = keyboard lockup 
Message-ID:  <199907230345.MAA01470@zodiac.mech.utsunomiya-u.ac.jp>
In-Reply-To: Your message of "Thu, 22 Jul 1999 21:33:34 -0400." <3797C66E.B9382583@toad.net> 
References:  <199907221845.LAA10738@usr05.primenet.com>  <3797C66E.B9382583@toad.net> 

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It is true that switching between X and text vtys fast by hitting
CTL-ALT-Fx repeatedly may cause keyboard lockup.

You can lock up the keyboard if you try to switch between them at the
*wrong* moment.  For example, many people have reported the keyboard
lockup when they tried to switch vtys while the X server is starting
up.

VT switching is a tricky business and the XFree86 servers and syscons,
from time to time, do not see each other in eye to eye...  

This is not I/O contention.  It is an algorithm problem.

# This, I believe, is mostly fixed in 4.0-CURRENT.

But, I do not believe this is the cause of your problem.  Because it
is the xdm/X server alone that is switching vtys when your keyboard
lockup happens.  You, the user, are not switching vtys when this is
happening.  Nor over-loaded I/O is the cause; the X server alone is
exercising inb()/outb() when your lockup happens.  There is no I/O
contention.

Kazu

>It looks like your suspiscions are correct.  After further attempts at
>starting
>xdm from a root seesion, it does in fact hang more often than not. Perhaps
>I was just "lucky" and it only worked with a quiet system.
>
>I'll try the ps test and see what I get
>
>-Rich
>
>Terry Lambert wrote:
>
>> > Wow! That's a lot to chew and mostly over my head, but a couple of
>> > questions..
>> >
>> > If what you say is true, then wouldn't I have toruble running xdm even
>> > from a root login after the boot process is over? I don't.
>>
>> No, not if the system is relatively quiescent.
>>
>> As I told Nate, you should be able to easily test this by loading
>> the I/O system (preferrably *not* your disks) and bouncing the
>> console in and out of X using ctrl-alt-F1/[ctrl-]alt-F4.  If it
>> locks up, the problem has been identified.
[...]



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