Re: Giant Locked drivers

On Tue, Nov 15, 2022 at 10:52 AM Steve Kargl <
sgk@troutmask.apl.washington.edu> wrote:

> On Tue, Nov 15, 2022 at 10:37:36AM -0700, Warner Losh wrote:
> >
> > It's no secret fiant-locked drivers' days are numbered. We've been more
> > sluggish about eliminating Giant than had been hoped. I plan in the
> coming
> > weeks to add a tunable 'debug.giant_drivers' which initially will be set
> to
> > enable/disable giant-locked drivers in the tree.
> >
> > When set to 0, you get today's behavior. If set to 1, it will no longer
> > allow drivers that don't request MPSAFE interrupt handlers from
> registering
> > (the interrupt setup will return an error).
> >
> > This will allow us to understand what is lost if we throw the switch, and
> > allow users to proactively test their systems to see if they are
> > affected or not (and if they are, if they want to live without the
> > functionality, or want to fund work in the area).
> >
> > Comments?
> >
>
> Is there a list of effected drivers?  Grepping /var/run/dmesg.boot
> on my system shows only "atkbd0: [GIANT-LOCKED]".  A scan of atkbd(4)
> shows
>
>    This driver is required for the console driver syscons(4) or vt(4).
>
> So, setting debug.giant_drivers=1 will brick all FreeBSD workstations?
>

You could still access them via serial port or the network.

And I think USB-based systems would be fine. The comment you quoted is
slightly overstated.

And yes, the point is to show the pain and get people to get off their !$#^
and do something if they care.

Warner