Re: Giant Locked drivers

From: Steve Kargl <>
Date: Tue, 15 Nov 2022 17:52:24 UTC
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)

   This driver is required for the console driver syscons(4) or vt(4).

So, setting debug.giant_drivers=1 will brick all FreeBSD workstations?