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

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Date:	Fri, 15 Apr 2016 07:33:34 +0800
From:	Boqun Feng <boqun.feng@...il.com>
To:	Waiman Long <waiman.long@....com>
Cc:	Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.com>,
	Jeff Layton <jlayton@...chiereds.net>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Tejun Heo <tj@...nel.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andi Kleen <andi@...stfloor.org>,
	Dave Chinner <dchinner@...hat.com>,
	Scott J Norton <scott.norton@....com>,
	Douglas Hatch <doug.hatch@....com>
Subject: Re: [PATCH v7 1/4] lib/percpu-list: Per-cpu list with associated
 per-cpu locks

On Wed, Apr 13, 2016 at 01:38:33PM -0400, Waiman Long wrote:
> 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.
> 

Given that a renaming will happen in the next version, carrying this as
a standalone patch will be a pain, I think. So feel free to squash this
into the patch #1, if that could make your job eariser ;-)

Regards,
Boqun

> Thanks,
> Longman
> 

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