linux-kernel - [PATCH 07/11] ipc,msg: introduce lockless functions to obtain the ipc object

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Date:	Wed, 15 May 2013 18:08:06 -0700
From:	Davidlohr Bueso <davidlohr.bueso@...com>
To:	akpm@...ux-foundation.org
Cc:	torvalds@...ux-foundation.org, riel@...hat.com,
	linux-kernel@...r.kernel.org,
	Davidlohr Bueso <davidlohr.bueso@...com>
Subject: [PATCH 07/11] ipc,msg: introduce lockless functions to obtain the ipc object

Add msq_obtain_object() and msq_obtain_object_check(), which will
allow us to get the ipc object without acquiring the lock. Just
as with semaphores, these functions are basically wrappers around
ipc_obtain_object*().

Signed-off-by: Davidlohr Bueso <davidlohr.bueso@...com>
---
 ipc/msg.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/ipc/msg.c b/ipc/msg.c
index 20361b5..9ff295b 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -166,6 +166,27 @@ static inline struct msg_queue *msg_lock_check(struct ipc_namespace *ns,
 	return container_of(ipcp, struct msg_queue, q_perm);
 }
 
+static inline struct msg_queue *msq_obtain_object(struct ipc_namespace *ns, int id)
+{
+	struct kern_ipc_perm *ipcp = ipc_obtain_object(&msg_ids(ns), id);
+
+	if (IS_ERR(ipcp))
+		return ERR_CAST(ipcp);
+
+	return container_of(ipcp, struct msg_queue, q_perm);
+}
+
+static inline struct msg_queue *msq_obtain_object_check(struct ipc_namespace *ns,
+							int id)
+{
+	struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&msg_ids(ns), id);
+
+	if (IS_ERR(ipcp))
+		return ERR_CAST(ipcp);
+
+	return container_of(ipcp, struct msg_queue, q_perm);
+}
+
 static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
 {
 	ipc_rmid(&msg_ids(ns), &s->q_perm);
-- 
1.7.11.7

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