Re: [PATCH 1/8] locking: Introduce local_lock()

Peter Zijlstra
2020-05-22T13:02:25Z

On Fri, May 22, 2020 at 01:05:56PM +0200, Sebastian Andrzej Siewior wrote:
> On 2020-05-20 14:04:50 [+0200], Peter Zijlstra wrote:
> > On Tue, May 19, 2020 at 10:19:05PM +0200, Sebastian Andrzej Siewior wrote:
> > > +/**
> > > + * DEFINE_LOCAL_LOCK - Define and initialize a per CPU local lock
> > > + * @lock: Name of the lock instance
> > > + */
> > > +#define DEFINE_LOCAL_LOCK(lvar) \
> > > + DEFINE_PER_CPU(struct local_lock, lvar) = { INIT_LOCAL_LOCK(lvar) }
> > > +
> > > +/**
> > > + * DECLARE_LOCAL_LOCK - Declare a defined per CPU local lock
> > > + * @lock: Name of the lock instance
> > > + */
> > > +#define DECLARE_LOCAL_LOCK(lvar) \
> > > + DECLARE_PER_CPU(struct local_lock, lvar)
> >
> > So I think I'm going to argue having these is a mistake. The local_lock
> > should be put in a percpu structure along with the data it actually
> > protects.
>
> So I got rid of these and made the local_lock part of the per-CPU
> struct.

Great!

> > > +#ifdef CONFIG_DEBUG_LOCK_ALLOC
> > > +# define LL_DEP_MAP_INIT(lockname) .dep_map = { .name = #lockname }
> >
> > That wants to be:
> >
> > .dep_map = {
> > .name = #lockname,
> > .wait_type_inner = LD_WAIT_SPIN,
>
> Why LD_WAIT_SPIN and not LD_WAIT_SLEEP? On RT the lock becomes sleeping
> and none of the SPIN restrictions apply.

Ah, then it wants to be LD_WAIT_CONFIG. I completely forgot what RT did
here.