Date: Thu, 22 Jul 1999 21:32:09 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: "Chris D. Faulhaber" <jedgar@fxp.org> Cc: Kazutaka YOKOTA <yokota@zodiac.mech.utsunomiya-u.ac.jp>, freebsd-smp@FreeBSD.ORG Subject: Re: SMP + XDM = keyboard lockup Message-ID: <199907230432.VAA21465@apollo.backplane.com> References: <Pine.BSF.4.10.9907230012350.13821-100000@pawn.primelocation.net>
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:> execution.
:>
:> If xdm happens to run before other getty processes, it may grab a vty
:> which will be eventually opened by a getty later.
:>
:
:vty's are assigned in /etc/ttys, though:
:
:ttyv4 "/usr/X11R6/bin/xdm -nodaemon" xterm off secure
:^^^^^
:so it the starting order shouldn't matter, unless you have a getty and xdm
:assigned the same vty, and then it _should_ lock up whether using SMP or
:not.
:
:-----
:Chris D. Faulhaber <jedgar@fxp.org> | All the true gurus I've met never
That's what I thought too... and it's correct for getty's. But xdm
ignores the argument init passes to it.
So here is what happens:
init opens the vty and runs xdm.
xdm runs X which ignores the vty and locates a new one by scanning
the vty's sequentially looking for one that is unused.
In this case a race is possible. X will not, in fact, run in vty 0
like we expected.
I tested this. My /etc/ttys runs xdm from ttyv0, but the X sessions
winds up on ttyv4.
However X does search vty's sequentially, so all you need to do is make
sure the first two slots in /etc/ttys for ttyv0 and ttyv1 are turned off.
So this is my recommendation now: Run xdm on ttyv0, leave ttyv1 turned
off. Run your getty's starting with ttyv2.
#
ttyv0 "/usr/X11R6/bin/xdm -nodaemon cons25 on secure
ttyv1 "/usr/libexec/getty Pc" cons25 off secure
ttyv2 "/usr/libexec/getty Pc" cons25 on secure
ttyv3 "/usr/libexec/getty Pc" cons25 on secure
Or, if you want to run xdm from your rc.local, leave both ttyv0
AND ttyv1 turned off. Why? Because ttyv0 will be allocated while
the rc files are being run so you still have to leave at least ttyv1
turned off in init to avoid a race.
If you do this I believe there is no possibility of a race.
It would be nice if we could specify the vty that X is to allocate
as an option to X. I couldn't find anything in the man pages right
offhand to accomplish this, though.
-Matt
Matthew Dillon
<dillon@backplane.com>
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