Re: Fix false positive by LOCKDEP_CROSSRELEASE

Bart Van Assche
2017-10-19T14:53:01Z

On Thu, 2017-10-19 at 10:57 +0900, Byungchul Park wrote:
> On Wed, Oct 18, 2017 at 02:29:56PM +0000, Bart Van Assche wrote:
> > On Wed, 2017-10-18 at 18:38 +0900, Byungchul Park wrote:
> > > Several false positives were reported, so I tried to fix them.
> > >
> > > It would be appreciated if you tell me if it works as expected, or let
> > > me know your opinion.
> >
> > What I have been wondering about is whether the crosslock checking makes
> > sense from a conceptual point of view. I tried to find documentation for the
> > crosslock checking in Documentation/locking/lockdep-design.txt but
> > couldn't find a description of the crosslock checking. Shouldn't it be
> > documented somewhere what the crosslock checks do and what the theory is
> > behind these checks?
>
> Documentation/locking/crossrelease.txt would be helpful.

That document is incomplete. It does not mention that although it can be
proven that the traditional lock validation code won't produce false
positives, that the cross-release checks do not have a solid theoretical
foundation and are prone to produce false positive reports.

Bart.