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

From: Davidlohr Bueso
Date: Wed May 15 2013 - 21:10:19 EST


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@xxxxxx>
---
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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