[PATCH] rculist.h: introduce list_entry_rcu and list_first_entry_rcu

[PATCH] rculist.h: introduce list_entry_rcu and list_first_entry_rcu

[Jiri Pirko]

I've run into the situation where I need to use list_first_entry with
rcu-guarded list. This patch introduces this. Also changed
list_for_each_entry_rcu to use new list_entry_rcu instead of list_entry.

Jirka

Signed-off-by: Jiri Pirko <jpirko@redhat.com>
---
 include/linux/rculist.h |   30 ++++++++++++++++++++++++++++--
 1 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index e649bd3..5710f43 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -198,6 +198,32 @@ static inline void list_splice_init_rcu(struct list_head *list,
 	at->prev = last;
 }
 
+/**
+ * list_entry_rcu - get the struct for this entry
+ * @ptr:        the &struct list_head pointer.
+ * @type:       the type of the struct this is embedded in.
+ * @member:     the name of the list_struct within the struct.
+ *
+ * This primitive may safely run concurrently with the _rcu list-mutation
+ * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
+ */
+#define list_entry_rcu(ptr, type, member) \
+	container_of(rcu_dereference(ptr), type, member)
+
+/**
+ * list_first_entry_rcu - get the first element from a list
+ * @ptr:        the list head to take the element from.
+ * @type:       the type of the struct this is embedded in.
+ * @member:     the name of the list_struct within the struct.
+ *
+ * Note, that list is expected to be not empty.
+ *
+ * This primitive may safely run concurrently with the _rcu list-mutation
+ * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
+ */
+#define list_first_entry_rcu(ptr, type, member) \
+	list_entry_rcu((ptr)->next, type, member)
+
 #define __list_for_each_rcu(pos, head) \
 	for (pos = rcu_dereference((head)->next); \
 		pos != (head); \
@@ -214,9 +240,9 @@ static inline void list_splice_init_rcu(struct list_head *list,
  * as long as the traversal is guarded by rcu_read_lock().
  */
 #define list_for_each_entry_rcu(pos, head, member) \
-	for (pos = list_entry(rcu_dereference((head)->next), typeof(*pos), member); \
+	for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \
 		prefetch(pos->member.next), &pos->member != (head); \
-		pos = list_entry(rcu_dereference(pos->member.next), typeof(*pos), member))
+		pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
 
 
 /**
-- 
1.6.0.6

Re: [PATCH] rculist.h: introduce list_entry_rcu and list_first_entry_rcu

[Paul E. McKenney]

On Tue, Apr 14, 2009 at 05:33:57PM +0200, Jiri Pirko wrote:
> I've run into the situation where I need to use list_first_entry with
> rcu-guarded list. This patch introduces this. Also changed
> list_for_each_entry_rcu to use new list_entry_rcu instead of list_entry.
> 
> Jirka

Looks good -- and very nice list_entry_rcu() primitive!

There are a couple more places where this primitive could be applied.
I would welcome a patch for these as well.

include/linux/sched.h next_task 1986 #define next_task(p) list_entry(rcu_dereference((p)->tasks.next), struct task_struct, tasks)
include/linux/sched.h next_thread 2025 return list_entry(rcu_dereference(p->thread_group.next),
ipc/sem.c exit_sem 1293 un = list_entry(rcu_dereference(ulp->list_proc.next),

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

> Signed-off-by: Jiri Pirko <jpirko@redhat.com>
> ---
>  include/linux/rculist.h |   30 ++++++++++++++++++++++++++++--
>  1 files changed, 28 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/rculist.h b/include/linux/rculist.h
> index e649bd3..5710f43 100644
> --- a/include/linux/rculist.h
> +++ b/include/linux/rculist.h
> @@ -198,6 +198,32 @@ static inline void list_splice_init_rcu(struct list_head *list,
>  	at->prev = last;
>  }
> 
> +/**
> + * list_entry_rcu - get the struct for this entry
> + * @ptr:        the &struct list_head pointer.
> + * @type:       the type of the struct this is embedded in.
> + * @member:     the name of the list_struct within the struct.
> + *
> + * This primitive may safely run concurrently with the _rcu list-mutation
> + * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
> + */
> +#define list_entry_rcu(ptr, type, member) \
> +	container_of(rcu_dereference(ptr), type, member)
> +
> +/**
> + * list_first_entry_rcu - get the first element from a list
> + * @ptr:        the list head to take the element from.
> + * @type:       the type of the struct this is embedded in.
> + * @member:     the name of the list_struct within the struct.
> + *
> + * Note, that list is expected to be not empty.
> + *
> + * This primitive may safely run concurrently with the _rcu list-mutation
> + * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
> + */
> +#define list_first_entry_rcu(ptr, type, member) \
> +	list_entry_rcu((ptr)->next, type, member)
> +
>  #define __list_for_each_rcu(pos, head) \
>  	for (pos = rcu_dereference((head)->next); \
>  		pos != (head); \
> @@ -214,9 +240,9 @@ static inline void list_splice_init_rcu(struct list_head *list,
>   * as long as the traversal is guarded by rcu_read_lock().
>   */
>  #define list_for_each_entry_rcu(pos, head, member) \
> -	for (pos = list_entry(rcu_dereference((head)->next), typeof(*pos), member); \
> +	for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \
>  		prefetch(pos->member.next), &pos->member != (head); \
> -		pos = list_entry(rcu_dereference(pos->member.next), typeof(*pos), member))
> +		pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
> 
> 
>  /**
> -- 
> 1.6.0.6
> 

Re: [PATCH] rculist.h: introduce list_entry_rcu and list_first_entry_rcu

[Jiri Pirko]

----- "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:
> There are a couple more places where this primitive could be applied.
> I would welcome a patch for these as well.
> 
Ok I will do this once this patch hits the tree.

Jirka

[tip:core/rcu] rculist.h: introduce list_entry_rcu() and list_first_entry_rcu()

[tip-bot for Jiri Pirko]

Commit-ID:  72c6a9870f901045f2464c3dc6ee8914bfdc07aa
Gitweb:     http://git.kernel.org/tip/72c6a9870f901045f2464c3dc6ee8914bfdc07aa
Author:     Jiri Pirko <jpirko@redhat.com>
AuthorDate: Tue, 14 Apr 2009 17:33:57 +0200
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 14 Apr 2009 18:41:15 +0200

rculist.h: introduce list_entry_rcu() and list_first_entry_rcu()

I've run into the situation where I need to use list_first_entry with
rcu-guarded list. This patch introduces this.

Also simplify list_for_each_entry_rcu() to use new list_entry_rcu()
instead of list_entry().

Signed-off-by: Jiri Pirko <jpirko@redhat.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: dipankar@in.ibm.com
LKML-Reference: <20090414153356.GC3999@psychotron.englab.brq.redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
 include/linux/rculist.h |   30 ++++++++++++++++++++++++++++--
 1 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index e649bd3..5710f43 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -198,6 +198,32 @@ static inline void list_splice_init_rcu(struct list_head *list,
 	at->prev = last;
 }
 
+/**
+ * list_entry_rcu - get the struct for this entry
+ * @ptr:        the &struct list_head pointer.
+ * @type:       the type of the struct this is embedded in.
+ * @member:     the name of the list_struct within the struct.
+ *
+ * This primitive may safely run concurrently with the _rcu list-mutation
+ * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
+ */
+#define list_entry_rcu(ptr, type, member) \
+	container_of(rcu_dereference(ptr), type, member)
+
+/**
+ * list_first_entry_rcu - get the first element from a list
+ * @ptr:        the list head to take the element from.
+ * @type:       the type of the struct this is embedded in.
+ * @member:     the name of the list_struct within the struct.
+ *
+ * Note, that list is expected to be not empty.
+ *
+ * This primitive may safely run concurrently with the _rcu list-mutation
+ * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
+ */
+#define list_first_entry_rcu(ptr, type, member) \
+	list_entry_rcu((ptr)->next, type, member)
+
 #define __list_for_each_rcu(pos, head) \
 	for (pos = rcu_dereference((head)->next); \
 		pos != (head); \
@@ -214,9 +240,9 @@ static inline void list_splice_init_rcu(struct list_head *list,
  * as long as the traversal is guarded by rcu_read_lock().
  */
 #define list_for_each_entry_rcu(pos, head, member) \
-	for (pos = list_entry(rcu_dereference((head)->next), typeof(*pos), member); \
+	for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \
 		prefetch(pos->member.next), &pos->member != (head); \
-		pos = list_entry(rcu_dereference(pos->member.next), typeof(*pos), member))
+		pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
 
 
 /**

Re: [PATCH] rculist.h: introduce list_entry_rcu and list_first_entry_rcu

[Ingo Molnar]

* Jiri Pirko <jpirko@redhat.com> wrote:

> ----- "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:
> > There are a couple more places where this primitive could be applied.
> > I would welcome a patch for these as well.
> > 
> Ok I will do this once this patch hits the tree.

it has just hit the RCU tree so feel free :)

  http://people.redhat.com/mingo/tip.git/README

	Ingo

Re: [PATCH] rculist.h: introduce list_entry_rcu and list_first_entry_rcu

[Paul E. McKenney]

On Tue, Apr 14, 2009 at 12:39:51PM -0400, Jiri Pirko wrote:
> ----- "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:
> > There are a couple more places where this primitive could be applied.
> > I would welcome a patch for these as well.
> > 
> Ok I will do this once this patch hits the tree.

Thank you!!!

							Thanx, Paul