Re: [PATCH rcu 12/12] refscale: Add srcu_read_lock_lite() support using "srcu-lite"

[Paul E. McKenney]

On Thu, Oct 10, 2024 at 05:38:34PM +0200, Frederic Weisbecker wrote:
> Le Wed, Oct 09, 2024 at 11:07:19AM -0700, Paul E. McKenney a écrit :
> > This commit creates a new srcu-lite option for the refscale.scale_type
> > module parameter that selects srcu_read_lock_lite() and
> > srcu_read_unlock_lite().
> > 
> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> > Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
> > Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > Cc: Kent Overstreet <kent.overstreet@xxxxxxxxx>
> > Cc: <bpf@xxxxxxxxxxxxxxx>
> 
> This one does not apply cleanly. I assume there is some dependency to another
> branch?

Quite possibly, since I made a stack rather than a set of branches.

I will branchify later today, make some updates from feedback, and
resend.

Apologies for the hassle!

							Thanx, Paul

> Thanks.
> 
> > ---
> >  kernel/rcu/refscale.c | 51 +++++++++++++++++++++++++++++++++----------
> >  1 file changed, 40 insertions(+), 11 deletions(-)
> > 
> > diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
> > index be66e5a67ee19..897d5b5494949 100644
> > --- a/kernel/rcu/refscale.c
> > +++ b/kernel/rcu/refscale.c
> > @@ -216,6 +216,36 @@ static const struct ref_scale_ops srcu_ops = {
> >  	.name		= "srcu"
> >  };
> >  
> > +static void srcu_lite_ref_scale_read_section(const int nloops)
> > +{
> > +	int i;
> > +	int idx;
> > +
> > +	for (i = nloops; i >= 0; i--) {
> > +		idx = srcu_read_lock_lite(srcu_ctlp);
> > +		srcu_read_unlock_lite(srcu_ctlp, idx);
> > +	}
> > +}
> > +
> > +static void srcu_lite_ref_scale_delay_section(const int nloops, const int udl, const int ndl)
> > +{
> > +	int i;
> > +	int idx;
> > +
> > +	for (i = nloops; i >= 0; i--) {
> > +		idx = srcu_read_lock_lite(srcu_ctlp);
> > +		un_delay(udl, ndl);
> > +		srcu_read_unlock_lite(srcu_ctlp, idx);
> > +	}
> > +}
> > +
> > +static const struct ref_scale_ops srcu_lite_ops = {
> > +	.init		= rcu_sync_scale_init,
> > +	.readsection	= srcu_lite_ref_scale_read_section,
> > +	.delaysection	= srcu_lite_ref_scale_delay_section,
> > +	.name		= "srcu-lite"
> > +};
> > +
> >  #ifdef CONFIG_TASKS_RCU
> >  
> >  // Definitions for RCU Tasks ref scale testing: Empty read markers.
> > @@ -1133,27 +1163,26 @@ ref_scale_init(void)
> >  	long i;
> >  	int firsterr = 0;
> >  	static const struct ref_scale_ops *scale_ops[] = {
> > -		&rcu_ops, &srcu_ops, RCU_TRACE_OPS RCU_TASKS_OPS &refcnt_ops, &rwlock_ops,
> > -		&rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, &sched_clock_ops, &clock_ops,
> > -		&jiffies_ops, &typesafe_ref_ops, &typesafe_lock_ops, &typesafe_seqlock_ops,
> > +		&rcu_ops, &srcu_ops, &srcu_lite_ops, RCU_TRACE_OPS RCU_TASKS_OPS
> > +		&refcnt_ops, &rwlock_ops, &rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops,
> > +		&sched_clock_ops, &clock_ops, &jiffies_ops, &typesafe_ref_ops, &typesafe_lock_ops,
> > +		&typesafe_seqlock_ops,
> >  	};
> >  
> >  	if (!torture_init_begin(scale_type, verbose))
> >  		return -EBUSY;
> >  
> >  	for (i = 0; i < ARRAY_SIZE(scale_ops); i++) {
> > -		cur_ops = scale_ops[i];
> > -		if (strcmp(scale_type, cur_ops->name) == 0)
> > +		cur_ops = scale_ops[i]; if (strcmp(scale_type,
> > +		cur_ops->name) == 0)
> >  			break;
> >  	}
> >  	if (i == ARRAY_SIZE(scale_ops)) {
> > -		pr_alert("rcu-scale: invalid scale type: \"%s\"\n", scale_type);
> > -		pr_alert("rcu-scale types:");
> > -		for (i = 0; i < ARRAY_SIZE(scale_ops); i++)
> > +		pr_alert("rcu-scale: invalid scale type: \"%s\"\n",
> > +		scale_type); pr_alert("rcu-scale types:"); for (i = 0;
> > +		i < ARRAY_SIZE(scale_ops); i++)
> >  			pr_cont(" %s", scale_ops[i]->name);
> > -		pr_cont("\n");
> > -		firsterr = -EINVAL;
> > -		cur_ops = NULL;
> > +		pr_cont("\n"); firsterr = -EINVAL; cur_ops = NULL;
> >  		goto unwind;
> >  	}
> >  	if (cur_ops->init)
> > -- 
> > 2.40.1
> >