Re: [PATCHv1 3/6] zsmalloc: make zspage lock preemptible

[Sergey Senozhatsky]

On (25/01/29 16:22), Uros Bizjak wrote:
> > +static void zspage_read_lock(struct zspage *zspage)
> > +{
> > +	atomic_t *lock = &zspage->lock;
> > +	int old;
> > +
> > +	while (1) {
> > +		old = atomic_read(lock);
> > +		if (old == ZS_PAGE_WRLOCKED) {
> > +			cpu_relax();
> > +			continue;
> > +		}
> > +
> > +		if (atomic_try_cmpxchg(lock, &old, old + 1))
> > +			return;
> > +
> > +		cpu_relax();
> > +	}
> > +}

[..]

> Based on the above, cpu_relax() should be removed from the loop, which
> becomes:
> 
> {
>         atomic_t *lock = &zspage->lock;
>         int old = atomic_read(lock);
> 
>         do {
>                 if (old == ZS_PAGE_WRLOCKED) {
>                         cpu_relax();
>                         old = atomic_read(lock);
>                         continue;
>                 }
> 
>         } while (!atomic_try_cmpxchg(lock, &old, old + 1));
>  }

Ack.

> > +static int zspage_try_write_lock(struct zspage *zspage)
> 
> This function can be declared as bool, returning true/false.

Ack.  Thank you.