Re: [PATCH v3 2/8] cxl/acpi: Add root device lockdep validation

From: Dan Williams
Date: Mon Apr 25 2022 - 12:06:14 EST

On Mon, Apr 25, 2022 at 3:33 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Sat, Apr 23, 2022 at 10:27:52AM -0700, Dan Williams wrote:
> > I'm going to drop it and just add a comment about the
> > expectations. As Peter said there's already a multitude of ways to
> > cause false positive / negative results with lockdep so this is just
> > one more area where one needs to be careful and understand the lock
> > context they might be overriding.
> One safe-guard might be to check the class you're overriding is indeed
> __no_validate__, and WARN if not. Then the unconditional reset is
> conistent.
> Then, if/when, that WARN ever triggers you can revisit all this.

Ok, that does seem to need a dummy definition of lockdep_match_class()
in the CONFIG_LOCKDEP=n case, but that seems worth it to me for the
sanity check.