Re: [PATCH] locktorture: Add raw_spinlock* torture tests for PREEMPT_RT kernels

From: Paul E. McKenney
Date: Wed Feb 22 2023 - 23:34:20 EST


On Wed, Feb 22, 2023 at 07:53:59PM -0800, Davidlohr Bueso wrote:
> On Wed, 22 Feb 2023, Paul E. McKenney wrote:
>
> > commit edc9d419ee8c22821ffd664466a5cf19208c3f02
> > Author: Zqiang <qiang1.zhang@xxxxxxxxx>
> > Date: Wed Feb 15 14:10:35 2023 +0800
> >
> > locktorture: Add raw_spinlock* torture tests for PREEMPT_RT kernels
> >
> > In PREEMPT_RT kernels, both spin_lock() and spin_lock_irq() are converted
> > to sleepable rt_spin_lock(). This means that the interrupt related suffix
> > for spin_lock/unlock(_irq, irqsave/irqrestore) do not affect the CPU's
> > interrupt state. This commit therefore adds raw spin-lock torture tests.
> > This in turn permits pure spin locks to be tested in PREEMPT_RT kernels.
> >
> > Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
>
> This is a nice addition, thanks. Just one comment below.
>
> > diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
> > index 9425aff089365..ed8e5baafe49f 100644
> > --- a/kernel/locking/locktorture.c
> > +++ b/kernel/locking/locktorture.c
> > @@ -257,6 +257,61 @@ static struct lock_torture_ops spin_lock_irq_ops = {
> > .name = "spin_lock_irq"
> > };
> >
> > +#ifdef CONFIG_PREEMPT_RT
> > +static DEFINE_RAW_SPINLOCK(torture_raw_spinlock);
>
> How about leaving raw spinlocks regardless of preempt-rt, and instead
> change the default lock (which is spin_lock) based on CONFIG_PREEMPT_RT
> and use the raw one in that case?

That makes a lot of sense to me! In fact, I tested this by deleting
those #ifdef statements. ;-)

Zqiang, would you like to take the patch and make that change, with
attribution?

Thanx, Paul