Re: [PATCH 03/32] locking/lockdep: lockdep_set_no_check_recursion()

Kent Overstreet
2023-05-09T20:36:01Z

On Tue, May 09, 2023 at 04:27:46PM -0400, Waiman Long wrote:
>
> On 5/9/23 16:18, Kent Overstreet wrote:
> > On Tue, May 09, 2023 at 09:31:47PM +0200, Peter Zijlstra wrote:
> > > On Tue, May 09, 2023 at 12:56:28PM -0400, Kent Overstreet wrote:
> > > > This adds a method to tell lockdep not to check lock ordering within a
> > > > lock class - but to still check lock ordering w.r.t. other lock types.
> > > >
> > > > This is for bcachefs, where for btree node locks we have our own
> > > > deadlock avoidance strategy w.r.t. other btree node locks (cycle
> > > > detection), but we still want lockdep to check lock ordering w.r.t.
> > > > other lock types.
> > > >
> > > ISTR you had a much nicer version of this where you gave a custom order
> > > function -- what happend to that?
> > Actually, I spoke too soon; this patch and the other series with the
> > comparison function solve different problems.
> >
> > For bcachefs btree node locks, we don't have a defined lock ordering at
> > all - we do full runtime cycle detection, so we don't want lockdep
> > checking for self deadlock because we're handling that but we _do_ want
> > lockdep checking lock ordering of btree node locks w.r.t. other locks in
> > the system.
>
> Maybe you can use lock_set_novalidate_class() instead.

No, we want that to go away, this is the replacement.