On Mon, May 27, 2019 at 06:06:18PM +0200, Peter Zijlstra wrote:
> On Mon, May 27, 2019 at 05:14:38PM +0200, Peter Zijlstra wrote:
> > On Fri, May 24, 2019 at 11:15:09PM +0300, Imre Deak wrote:
> > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> > > index 967352d32af1..9e2a4ab6c731 100644
> > > --- a/kernel/locking/lockdep.c
> > > +++ b/kernel/locking/lockdep.c
> > > @@ -3637,6 +3637,11 @@ print_lock_nested_lock_not_held(struct task_struct
> > > *curr,
> > >
> > > static int __lock_is_held(const struct lockdep_map *lock, int read);
> > >
> > > +static int hlock_reference(int reference)
> > > +{
> > > + return reference ? : 1;
> > > +}
> > > +
> > > /*
> > > * This gets called for every mutex_lock*()/spin_lock*() operation.
> > > * We maintain the dependency maps and validate the locking attempt:
> > > @@ -3702,17 +3707,15 @@ static int __lock_acquire(struct lockdep_map
> > > *lock, unsigned int subclass,
> > > if (depth) {
> > > hlock = curr->held_locks + depth - 1;
> > > if (hlock->class_idx == class_idx && nest_lock) {
> > > - if (hlock->references) {
> > > - /*
> > > - * Check: unsigned int references overflow.
> > > - */
> > > - if (DEBUG_LOCKS_WARN_ON(hlock->references ==
> > > UINT_MAX))
> >
> > What tree is this against? Afaict this is still 12 bits ?!
> >
> > > - return 0;
> > > + /*
> > > + * Check: unsigned int references overflow.
> > > + */
> > > + if
> > > (DEBUG_LOCKS_WARN_ON(hlock_reference(hlock->references) >
> > > + UINT_MAX -
> > > hlock_reference(references)))
> >
> > Idem. Also very weird overflow check..
> >
> > > + return 0;
> > >
> > > - hlock->references++;
> > > - } else {
> > > - hlock->references = 2;
> > > - }
> > > + hlock->references = hlock_reference(hlock->references) +
> > > + hlock_reference(references);
> > >
> > > return 2;
> > > }
>
> I think you wanted something like this: ?
>
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -3731,6 +3731,11 @@ print_lock_nested_lock_not_held(struct t
>
> static int __lock_is_held(const struct lockdep_map *lock, int read);
>
> +static inline int hlock_references(struct held_lock *hlock)
> +{
> + return hlock->references ? : 1;
> +}
> +
> /*
> * This gets called for every mutex_lock*()/spin_lock*() operation.
> * We maintain the dependency maps and validate the locking attempt:
> @@ -3796,17 +3801,14 @@ static int __lock_acquire(struct lockdep
> if (depth) {
> hlock = curr->held_locks + depth - 1;
> if (hlock->class_idx == class_idx && nest_lock) {
> - if (hlock->references) {
> - /*
> - * Check: unsigned int references:12, overflow.
> - */
> - if (DEBUG_LOCKS_WARN_ON(hlock->references == (1
> << 12)-1))
> - return 0;
> -
> - hlock->references++;
> - } else {
> - hlock->references = 2;
> - }
> + if (!references)
> + references++;
> +
> + hlock->references = hlock_references(hlock) +
> references;
> +
> + /* Overflow */
> + if (DEBUG_LOCKS_WARN_ON(hlock->references < references))
> + return 0;
Yes, it works.
>
> return 2;
> }
