diff mbox

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

Message ID 20160413020929.GA23058@fixme-laptop.cn.ibm.com (mailing list archive)
State New, archived
Headers show

Commit Message

Boqun Feng April 13, 2016, 2:09 a.m. UTC 
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?

Regards,
Boqun

-------------------------------------------->8
From: Boqun Feng <boqun.feng@gmail.com>
Date: Wed, 13 Apr 2016 09:49:13 +0800
Subject: [PATCH] lib/percpu-list: Add __percpu modifier for parameters

Add __percpu modifier properly to help:

1.	Differ pointers to actual structures with those to percpu
	structures, which could improve readability.

2. 	Prevent sparse from complaining about "different address spaces"

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
 include/linux/percpu-list.h | 16 +++++++++-------
 lib/percpu-list.c           |  8 +++++---
 2 files changed, 14 insertions(+), 10 deletions(-)

Comments

Waiman Long April 13, 2016, 5:38 p.m. UTC | #1 
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

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Boqun Feng April 14, 2016, 11:33 p.m. UTC | #2 
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
>
Waiman Long April 15, 2016, 5:14 p.m. UTC | #3 
On 04/14/2016 07:33 PM, Boqun Feng wrote:
> 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
>
>

That is not a problem. I do want to acknowledge your contribution to 
this patchset.

Cheers,
Longman
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diff mbox

Patch

diff --git a/include/linux/percpu-list.h b/include/linux/percpu-list.h
index ce8238a78198..4c8496004dc2 100644
--- a/include/linux/percpu-list.h
+++ b/include/linux/percpu-list.h
@@ -107,7 +107,8 @@  static inline void init_pcpu_list_node(struct pcpu_list_node *node)
 	node->lockptr = NULL;
 }
 
-static inline void free_pcpu_list_head(struct pcpu_list_head **ppcpu_head)
+static inline void
+free_pcpu_list_head(struct pcpu_list_head __percpu **ppcpu_head)
 {
 	free_percpu(*ppcpu_head);
 	*ppcpu_head = NULL;
@@ -116,7 +117,7 @@  static inline void free_pcpu_list_head(struct pcpu_list_head **ppcpu_head)
 /*
  * Check if all the per-cpu lists are empty
  */
-static inline bool pcpu_list_empty(struct pcpu_list_head *pcpu_head)
+static inline bool pcpu_list_empty(struct pcpu_list_head __percpu *pcpu_head)
 {
 	int cpu;
 
@@ -133,7 +134,8 @@  static inline bool pcpu_list_empty(struct pcpu_list_head *pcpu_head)
  * Return: true if the entry is found, false if all the lists exhausted
  */
 static __always_inline bool
-__pcpu_list_next_cpu(struct pcpu_list_head *head, struct pcpu_list_state *state)
+__pcpu_list_next_cpu(struct pcpu_list_head __percpu *head,
+		     struct pcpu_list_state *state)
 {
 	if (state->lock)
 		spin_unlock(state->lock);
@@ -170,7 +172,7 @@  next_cpu:
  *
  * Return: true if the next entry is found, false if all the entries iterated
  */
-static inline bool pcpu_list_iterate(struct pcpu_list_head *head,
+static inline bool pcpu_list_iterate(struct pcpu_list_head __percpu *head,
 				     struct pcpu_list_state *state)
 {
 	/*
@@ -198,7 +200,7 @@  static inline bool pcpu_list_iterate(struct pcpu_list_head *head,
  *
  * Return: true if the next entry is found, false if all the entries iterated
  */
-static inline bool pcpu_list_iterate_safe(struct pcpu_list_head *head,
+static inline bool pcpu_list_iterate_safe(struct pcpu_list_head __percpu *head,
 					  struct pcpu_list_state *state)
 {
 	/*
@@ -224,8 +226,8 @@  static inline bool pcpu_list_iterate_safe(struct pcpu_list_head *head,
 }
 
 extern void pcpu_list_add(struct pcpu_list_node *node,
-			  struct pcpu_list_head *head);
+			  struct pcpu_list_head __percpu *head);
 extern void pcpu_list_del(struct pcpu_list_node *node);
-extern int  init_pcpu_list_head(struct pcpu_list_head **ppcpu_head);
+extern int  init_pcpu_list_head(struct pcpu_list_head __percpu **ppcpu_head);
 
 #endif /* __LINUX_PERCPU_LIST_H */
diff --git a/lib/percpu-list.c b/lib/percpu-list.c
index 8a9600169966..ef2bcb8e5a1b 100644
--- a/lib/percpu-list.c
+++ b/lib/percpu-list.c
@@ -27,9 +27,10 @@  static struct lock_class_key percpu_list_key;
 /*
  * Initialize the per-cpu list head
  */
-int init_pcpu_list_head(struct pcpu_list_head **ppcpu_head)
+int init_pcpu_list_head(struct pcpu_list_head __percpu **ppcpu_head)
 {
-	struct pcpu_list_head *pcpu_head = alloc_percpu(struct pcpu_list_head);
+	struct pcpu_list_head __percpu *pcpu_head =
+				alloc_percpu(struct pcpu_list_head);
 	int cpu;
 
 	if (!pcpu_head)
@@ -52,7 +53,8 @@  int init_pcpu_list_head(struct pcpu_list_head **ppcpu_head)
  * function is called. However, deletion may be done by a different CPU.
  * So we still need to use a lock to protect the content of the list.
  */
-void pcpu_list_add(struct pcpu_list_node *node, struct pcpu_list_head *head)
+void pcpu_list_add(struct pcpu_list_node *node,
+		   struct pcpu_list_head __percpu *head)
 {
 	struct pcpu_list_head *myhead;