[dpdk-dev] [PATCH v2 2/2] ring: introduce rte_ring_init()

[Olivier Matz <olivier.matz@6wind.com>]

Allow to initialize a ring in an already allocated memory. The rte_ring_create()
function that allocates a ring in a rte_memzone is still available and now uses
the new rte_ring_init() function in order to factorize the code.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
---
 lib/librte_ring/rte_ring.c | 63 ++++++++++++++++++++++++++--------------------
 lib/librte_ring/rte_ring.h | 51 +++++++++++++++++++++++++++++++++----
 2 files changed, 82 insertions(+), 32 deletions(-)

diff --git a/lib/librte_ring/rte_ring.c b/lib/librte_ring/rte_ring.c
index 156fe49..2eaa6c8 100644
--- a/lib/librte_ring/rte_ring.c
+++ b/lib/librte_ring/rte_ring.c
@@ -113,18 +113,10 @@ rte_ring_get_memsize(unsigned count)
 	return sz;
 }
 
-/* create the ring */
-struct rte_ring *
-rte_ring_create(const char *name, unsigned count, int socket_id,
-		unsigned flags)
+int
+rte_ring_init(struct rte_ring *r, const char *name, unsigned count,
+	unsigned flags)
 {
-	char mz_name[RTE_MEMZONE_NAMESIZE];
-	struct rte_ring *r;
-	const struct rte_memzone *mz;
-	ssize_t ring_size;
-	int mz_flags = 0;
-	struct rte_ring_list* ring_list = NULL;
-
 	/* compilation-time checks */
 	RTE_BUILD_BUG_ON((sizeof(struct rte_ring) &
 			  CACHE_LINE_MASK) != 0);
@@ -141,11 +133,38 @@ rte_ring_create(const char *name, unsigned count, int socket_id,
 			  CACHE_LINE_MASK) != 0);
 #endif
 
+	/* init the ring structure */
+	memset(r, 0, sizeof(*r));
+	rte_snprintf(r->name, sizeof(r->name), "%s", name);
+	r->flags = flags;
+	r->prod.watermark = count;
+	r->prod.sp_enqueue = !!(flags & RING_F_SP_ENQ);
+	r->cons.sc_dequeue = !!(flags & RING_F_SC_DEQ);
+	r->prod.size = r->cons.size = count;
+	r->prod.mask = r->cons.mask = count-1;
+	r->prod.head = r->cons.head = 0;
+	r->prod.tail = r->cons.tail = 0;
+
+	return 0;
+}
+
+/* create the ring */
+struct rte_ring *
+rte_ring_create(const char *name, unsigned count, int socket_id,
+		unsigned flags)
+{
+	char mz_name[RTE_MEMZONE_NAMESIZE];
+	struct rte_ring *r;
+	const struct rte_memzone *mz;
+	ssize_t ring_size;
+	int mz_flags = 0;
+	struct rte_ring_list* ring_list = NULL;
+
 	/* check that we have an initialised tail queue */
-	if ((ring_list = 
+	if ((ring_list =
 	     RTE_TAILQ_LOOKUP_BY_IDX(RTE_TAILQ_RING, rte_ring_list)) == NULL) {
 		rte_errno = E_RTE_NO_TAILQ;
-		return NULL;	
+		return NULL;
 	}
 
 	ring_size = rte_ring_get_memsize(count);
@@ -164,26 +183,16 @@ rte_ring_create(const char *name, unsigned count, int socket_id,
 	mz = rte_memzone_reserve(mz_name, ring_size, socket_id, mz_flags);
 	if (mz != NULL) {
 		r = mz->addr;
-
-		/* init the ring structure */
-		memset(r, 0, sizeof(*r));
-		rte_snprintf(r->name, sizeof(r->name), "%s", name);
-		r->flags = flags;
-		r->prod.watermark = count;
-		r->prod.sp_enqueue = !!(flags & RING_F_SP_ENQ);
-		r->cons.sc_dequeue = !!(flags & RING_F_SC_DEQ);
-		r->prod.size = r->cons.size = count;
-		r->prod.mask = r->cons.mask = count-1;
-		r->prod.head = r->cons.head = 0;
-		r->prod.tail = r->cons.tail = 0;
-
+		/* no need to check return value here, we already checked the
+		 * arguments above */
+		rte_ring_init(r, name, count, flags);
 		TAILQ_INSERT_TAIL(ring_list, r, next);
 	} else {
 		r = NULL;
 		RTE_LOG(ERR, RING, "Cannot reserve memory\n");
 	}
 	rte_rwlock_write_unlock(RTE_EAL_TAILQ_RWLOCK);
-	
+
 	return r;
 }
 
diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h
index e8493f2..96232d3 100644
--- a/lib/librte_ring/rte_ring.h
+++ b/lib/librte_ring/rte_ring.h
@@ -215,13 +215,54 @@ struct rte_ring {
 ssize_t rte_ring_get_memsize(unsigned count);
 
 /**
+ * Initialize a ring structure.
+ *
+ * Initialize a ring structure in memory pointed by "r". The size of the
+ * memory area must be large enough to store the ring structure and the
+ * object table. It is advised to use rte_ring_get_memsize() to get the
+ * appropriate size.
+ *
+ * The ring size is set to *count*, which must be a power of two. Water
+ * marking is disabled by default. The real usable ring size is
+ * *count-1* instead of *count* to differentiate a free ring from an
+ * empty ring.
+ *
+ * The ring is not added in RTE_TAILQ_RING global list. Indeed, the
+ * memory given by the caller may not be shareable among dpdk
+ * processes.
+ *
+ * @param r
+ *   The pointer to the ring structure followed by the objects table.
+ * @param name
+ *   The name of the ring.
+ * @param count
+ *   The number of elements in the ring (must be a power of 2).
+ * @param flags
+ *   An OR of the following:
+ *    - RING_F_SP_ENQ: If this flag is set, the default behavior when
+ *      using ``rte_ring_enqueue()`` or ``rte_ring_enqueue_bulk()``
+ *      is "single-producer". Otherwise, it is "multi-producers".
+ *    - RING_F_SC_DEQ: If this flag is set, the default behavior when
+ *      using ``rte_ring_dequeue()`` or ``rte_ring_dequeue_bulk()``
+ *      is "single-consumer". Otherwise, it is "multi-consumers".
+ * @return
+ *   0 on success, or a negative value on error.
+ */
+int rte_ring_init(struct rte_ring *r, const char *name, unsigned count,
+	unsigned flags);
+
+/**
  * Create a new ring named *name* in memory.
  *
- * This function uses ``memzone_reserve()`` to allocate memory. Its size is
- * set to *count*, which must be a power of two. Water marking is
- * disabled by default.
- * Note that the real usable ring size is *count-1* instead of
- * *count*.
+ * This function uses ``memzone_reserve()`` to allocate memory. Then it
+ * calls rte_ring_init() to initialize an empty ring.
+ *
+ * The new ring size is set to *count*, which must be a power of
+ * two. Water marking is disabled by default. The real usable ring size
+ * is *count-1* instead of *count* to differentiate a free ring from an
+ * empty ring.
+ *
+ * The ring is added in RTE_TAILQ_RING list.
  *
  * @param name
  *   The name of the ring.
-- 
1.9.2