Re: [PATCH v7 1/4] lib/percpu-list: Per-cpu list with associated per-cpu locks

[Waiman Long]

On 04/12/2016 10:09 PM, Boqun Feng wrote:
> Hi Waiman,
>
> On Tue, Apr 12, 2016 at 06:54:43PM -0400, Waiman Long wrote:
> [...]
> > +
> > +/*
> > + * Initialize the per-cpu list head
> > + */
> > +int init_pcpu_list_head(struct pcpu_list_head **ppcpu_head)
> > +{
> > +	struct pcpu_list_head *pcpu_head = alloc_percpu(struct pcpu_list_head);
> > +	int cpu;
> > +
> > +	if (!pcpu_head)
> > +		return -ENOMEM;
> > +
> > +	for_each_possible_cpu(cpu) {
> > +		struct pcpu_list_head *head = per_cpu_ptr(pcpu_head, cpu);
> > +
> > +		INIT_LIST_HEAD(&head->list);
> > +		head->lock = __SPIN_LOCK_UNLOCKED(&head->lock);
> > +		lockdep_set_class(&head->lock,&percpu_list_key);
> > +	}
> > +
> > +	*ppcpu_head = pcpu_head;
> > +	return 0;
> > +}
> The first time I looked at this patch, I had a hard time to figure out
> which "struct pcpu_list_head" pointer is pointing to percpu data(the
> pointer could be the parameter for per/this_cpu_ptr()), and which
> pointer is pointing to actual structure. For example, 'pcpu_head' and
> 'head' above are different types of pointers.
>
> So besides improving my code reading skills, I think the following patch
> helps ;-) Also it can resolve several splats of sparse when running
> 'make C=1 lib/'.
>
> Thoughts?

Yes, I think your patch is helpful. I will include your patch in my 
patchset.

Thanks,
Longman