Re: [PATCH] locking/locktorture: reject zero resolved worker threads

[Paul E. McKenney]

On Sun, Jun 07, 2026 at 10:26:03AM -0400, Samuel Moelius wrote:
> On Fri, Jun 5, 2026 at 10:46 PM Paul E. McKenney <paulmck@xxxxxxxxxx> wrote:
> >
> > On Fri, Jun 05, 2026 at 06:47:05PM +0000, Samuel Moelius wrote:
> > > locktorture checks for a zero-worker configuration before it resolves
> > > the default reader count.  For reader-capable lock types, a user can
> > > pass nwriters_stress=0 and leave nreaders_stress at its default -1.
> > > This bypasses the early check, then derives the default real reader
> > > count from the real writer count, leaving both resolved counts at zero.
> > >
> > > The module can then load successfully, optionally creating helper
> > > threads such as the stats thread, but no lock-torture worker threads.
> > >
> > > Reject the resolved zero-worker state after reader defaults have been
> > > applied.
> > >
> > > Assisted-by: Codex:gpt-5.5-cyber-preview
> > > Signed-off-by: Samuel Moelius <sam.moelius@xxxxxxxxxxxxxxx>
> > > ---
> > >  kernel/locking/locktorture.c | 7 +++++++
> > >  1 file changed, 7 insertions(+)
> > >
> > > diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
> > > index e618bcf75e2d..7d553ecd3fab 100644
> > > --- a/kernel/locking/locktorture.c
> > > +++ b/kernel/locking/locktorture.c
> > > @@ -1320,6 +1320,13 @@ static int __init lock_torture_init(void)
> > >                       cxt.nrealreaders_stress = cxt.nrealwriters_stress;
> > >               }
> > >
> > > +             if (cxt.nrealwriters_stress == 0 &&
> > > +                 cxt.nrealreaders_stress == 0) {
> > > +                     pr_alert("lock-torture: must run at least one locking thread\n");
> > > +                     firsterr = -EINVAL;
> > > +                     goto unwind;
> > > +             }
> > > +
> > >               if (nreaders_stress) {
> > >                       cxt.lrsa = kmalloc_objs(*cxt.lrsa,
> > >                                               cxt.nrealreaders_stress);
> >
> > Fair point!
> >
> > Though if we are to fully handle erroneous combinations of module
> > parameters to this debug module, there is also later code that updates
> > cxt.nrealwriters_stress *after* having allocated and initialized the
> > cxt.lwsa array.  And likely other issues.
> >
> > Would you be willing to review lock_torture_init() to fix all aspects of
> > its error handling?  If we do it one at a time, we will after all likely
> > go in circles for some time.  And that won't be fun for any of us.  ;-)
> 
> Your point is well taken regarding this being a debug module. But I
> have limited access to the gpt-5.5-cyber model, and my goal is to find
> as many bugs with it in the time that I have. Could I respectfully
> request that this patch be considered in isolation?

If I get time to bring this module's error checking out of expert-only
mode, I will of course give you a Reported-by.

							Thanx, Paul