NetBSD Problem Report #44712

From dholland@macaran.localdomain  Sat Mar 12 03:33:36 2011
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Date: Fri, 11 Mar 2011 22:33:33 -0500 (EST)
Subject: wscons VT switching gets wedged
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>Number:         44712
>Category:       kern
>Synopsis:       wscons VT switching gets wedged
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Mar 12 03:35:00 +0000 2011
>Last-Modified:  Fri Dec 23 05:29:59 +0000 2011
>Originator:     David A. Holland
>Release:        NetBSD 5.99.41 (20101130)
System: NetBSD macaran 5.99.41 NetBSD 5.99.41 (MACARAN) #3: Tue Nov 30 21:52:01 EST 2010 dholland@macaran:/usr/src/sys/arch/amd64/compile/MACARAN amd64
Architecture: x86_64
Machine: amd64

Tonight while starting an X server (on screen 1; there was another one
running as screen 0, which might or might not be important) I hit
ctrl-alt-f1 at, apparently, just the wrong time. This left wscons
unable to switch VTs. Hitting ctrl-alt-Fn (for any n) did nothing;
explicitly switching with wsconscfg(*) yielded EBUSY.

It looks as if the EBUSY comes from line 1943 of wsdisplay.c, meaning
that the SC_SWITCHPENDING flag got set and some race condition
associated with starting up the X server caused the operation that's
supposed to clear the flag to get lost.

The EBUSY might instead be coming from line 1972 but I don't think so
judging from what SCR_GRAPHICS is documented to mean and the fact that
I have an ordinary x86 text console.

On the other hand it looks as if SC_SWITCHPENDING should be cleared by
suspending and resuming wsdisplay0. I tried to do that and couldn't
get it to do anything; but maybe I was doing it wrong.

(*) (Why is this functionality found in wscons*cfg* rather than


as above.




From: David Holland <>
Subject: Re: xsrc/44712: wscons VT switching gets wedged
Date: Fri, 23 Dec 2011 05:10:14 +0000

 On Sat, Mar 12, 2011 at 03:35:00AM +0000, wrote:
  > >Synopsis:       wscons VT switching gets wedged

 Ran into this again tonight, so it's still a live issue at least as of

 May also be the same as PR 22423.

 David A. Holland

Responsible-Changed-From-To: xsrc-manager->kern-bug-people
Responsible-Changed-When: Fri, 23 Dec 2011 05:29:59 +0000
regardless of what the X server may be doing, the bug is in wscons


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