On Fri, 7 Jul 2006 23:23:07 +0200 "Rafael J. Wysocki" <[EMAIL PROTECTED]> wrote:
> On Friday 07 July 2006 21:13, Rafael J. Wysocki wrote:
> > On Friday 07 July 2006 15:02, Tim Dijkstra wrote:
> > > On Fri, 7 Jul 2006 14:44:19 +0200
> > > "Rafael J. Wysocki" <[EMAIL PROTECTED]> wrote:
> > >
> > > > On Friday 07 July 2006 14:30, Tim Dijkstra wrote:
> > > > > On Fri, 7 Jul 2006 13:25:20 +0200
> > > > > "Rafael J. Wysocki" <[EMAIL PROTECTED]> wrote:
> > > > >
> > > > > > Hi,
> > > > > >
> > > > > > Apparently we have used wrond console ioctls around
> > > > > > freeze() in suspend_system() and in a wrong order. The
> > > > > > appended patch fixes this.
> > > > > >
> > > > > > Comments welcome.
> > > > >
> > > > > Just some questions. You told me this was a hack to get the
> > > > > user not to switch VTs.
> > > > >
> > > > > I guess the VT_ACTIVATE before the freeze is need because we
> > > > > can't be sure the user didn't switch since the last time with
> > > > > switched. Is the second needed, because there is a (slim)
> > > > > chance they did just before the freeze after the first
> > > > > VT_ACTIVATE?
> > > >
> > > > It just returns to the previous state.
> > >
> > > Because freeze will mess with the VT state?
> >
> > It shouldn't, but generally we can't assume it never will.
> >
> > > > I think even if the user manages to
> > > > trigger the switch after the first VT_ACTIVATE, it won't hurt
> > > > us after the second VT_ACTIVATE, because X is now frozen and it
> > > > won't take over the hardware.
> > >
> > > > > Why do we switch to KD_GRAPHIC just before freeze and KD_TEXT
> > > > > just after? Shouldn't we KDGETMODE and restore that?
> > > >
> > > > prepare_console() is supposed to leave is in KD_TEXT. However
> > > > it's probably a good idea to use KDGETMODE anyway.
> > >
> > > I did a bit of reading on this, isn't using VT_SETMODE to set
> > > VT_PROCESS precisely what we want? If I read it correctly that
> > > will block all VT switching unless we issue the VT_RELDISP ioctl.
> >
> > Well, that should work, at least at first sight.
>
> At the second sight, however, it looks like after VT_PROCESS the
> kernel will block switching _to_ the VT in question and not _from_
> it, and we're trying to prevent the latter from happening here.
Hmm, maybe your right. I was reading this
The "switch-from" process will need to perform any cleanup, and
issue the VT_RELDISP ioctl, telling the kernel that it is OK to
continue the switch. It is also possible for it to deny the
switch, in which case the kernel discontinues the switch.
But maybe this is only true if the _to_ process set the VT_PROCESS,
seems odd though. There should also be a way to prevent switching
from. Maybe I'll try and test this tomorrow.
grts Tim
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