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Date: Wed, 13 Apr 2016 10:09:29 +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
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@...il.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@...il.com>
---
include/linux/percpu-list.h | 16 +++++++++-------
lib/percpu-list.c | 8 +++++---
2 files changed, 14 insertions(+), 10 deletions(-)
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;
--
2.8.0
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