Re: Giant Locked drivers

In reply to: Warner Losh : "Giant Locked drivers"
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From: Ed Maste <emaste_at_freebsd.org>
Date: Tue, 15 Nov 2022 17:56:46 UTC

On Tue, 15 Nov 2022 at 12:37, Warner Losh <imp@bsdimp.com> wrote:
>
> Greetings,
>
> It's no secret Giant-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).

I think having such a tunable is a good idea, but let's use
positive-sense sysctls, so that we set the enable sysctl to 1 to allow
Giant-locked drivers and to 0 to disable.