Re: check && lockdep_no_validate (Was: lockdep: Introducewait-type checks)

[Oleg Nesterov]

On 01/12, Peter Zijlstra wrote:
>
> On Thu, Jan 09, 2014 at 06:54:48PM +0100, Oleg Nesterov wrote:
> >
> > --- a/kernel/locking/lockdep.c
> > +++ b/kernel/locking/lockdep.c
> > @@ -1939,7 +1939,8 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next)
> >  		 * Only non-recursive-read entries get new dependencies
> >  		 * added:
> >  		 */
> > -		if (hlock->read != 2) {
> > +		if (hlock->read != 2 &&
> > +		    hlock->instance->key != &__lockdep_no_validate__) {
> >  			if (!check_prev_add(curr, hlock, next,
> >  						distance, trylock_loop))
> >  				return 0;
> >
>
> Hmm, you are quite right indeed;

Thanks!

> although I would write it like:
>
>   if (hlock->read != 2 && hlock->check == 2)
>
> because the __lockdep_no_validate__ thing forces the ->check value to 1.

Agreed, hlock->check == 2 looks better. But this connects to another
patch I sent which removes hlock->check...

OK, I'll wait for review on that patch, then resend this one with
->check or __lockdep_no_validate__ depending on the result.

Oleg.

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