linux-kernel - Re: [PATCH] locktorture: Add raw_spinlock* torture tests for PREEMPT

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Date:   Wed, 22 Feb 2023 20:34:11 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     "Zhang, Qiang1" <qiang1.zhang@...el.com>,
        "josh@...htriplett.org" <josh@...htriplett.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] locktorture: Add raw_spinlock* torture tests for
 PREEMPT_RT kernels

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@...el.com>
> > 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@...el.com>
> >    Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> 
> 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