svm: add unidirectional message queue

Meant for single reader/writer message exchanges. Supports multiple
message rings.

Change-Id: I925de9a6ae19226c5c39a63caff76424ed123a13
Signed-off-by: Florin Coras <fcoras@cisco.com>

1 files changed, 159 insertions, 0 deletions

diff --git a/src/svm/message_queue.c b/src/svm/message_queue.c
new file mode 100644
index 00000000000..dc0f6251120
--- /dev/null
+++ b/src/svm/message_queue.c
@@ -0,0 +1,159 @@
+/*
+ * Copyright (c) 2018 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <svm/message_queue.h>
+#include <vppinfra/mem.h>
+
+svm_msg_q_t *
+svm_msg_q_alloc (svm_msg_q_cfg_t * cfg)
+{
+  svm_msg_q_ring_t *ring;
+  svm_msg_q_t *mq;
+  int i;
+
+  if (!cfg)
+    return 0;
+
+  mq = clib_mem_alloc_aligned (sizeof (svm_msg_q_t), CLIB_CACHE_LINE_BYTES);
+  memset (mq, 0, sizeof (*mq));
+  mq->q = svm_queue_init (cfg->q_nitems, sizeof (svm_msg_q_msg_t),
+			  cfg->consumer_pid, 0);
+  vec_validate (mq->rings, cfg->n_rings - 1);
+  for (i = 0; i < cfg->n_rings; i++)
+    {
+      ring = &mq->rings[i];
+      ring->elsize = cfg->ring_cfgs[i].elsize;
+      ring->nitems = cfg->ring_cfgs[i].nitems;
+      if (cfg->ring_cfgs[i].data)
+	ring->data = cfg->ring_cfgs[i].data;
+      else
+	ring->data = clib_mem_alloc_aligned (ring->nitems * ring->elsize,
+					     CLIB_CACHE_LINE_BYTES);
+    }
+
+  return mq;
+}
+
+void
+svm_msg_q_free (svm_msg_q_t * mq)
+{
+  svm_msg_q_ring_t *ring;
+
+  vec_foreach (ring, mq->rings)
+  {
+    clib_mem_free (ring->data);
+  }
+  vec_free (mq->rings);
+  clib_mem_free (mq);
+}
+
+svm_msg_q_msg_t
+svm_msg_q_alloc_msg (svm_msg_q_t * mq, u32 nbytes)
+{
+  svm_msg_q_msg_t msg = {.as_u64 = ~0 };
+  svm_msg_q_ring_t *ring;
+
+  vec_foreach (ring, mq->rings)
+  {
+    if (ring->elsize < nbytes || ring->cursize == ring->nitems)
+      continue;
+    msg.ring_index = ring - mq->rings;
+    msg.elt_index = ring->tail;
+    ring->tail = (ring->tail + 1) % ring->nitems;
+    __sync_fetch_and_add (&ring->cursize, 1);
+    break;
+  }
+  return msg;
+}
+
+static inline svm_msg_q_ring_t *
+svm_msg_q_get_ring (svm_msg_q_t * mq, u32 ring_index)
+{
+  return vec_elt_at_index (mq->rings, ring_index);
+}
+
+static inline void *
+svm_msg_q_ring_data (svm_msg_q_ring_t * ring, u32 elt_index)
+{
+  ASSERT (elt_index < ring->nitems);
+  return (ring->data + elt_index * ring->elsize);
+}
+
+void *
+svm_msg_q_msg_data (svm_msg_q_t * mq, svm_msg_q_msg_t * msg)
+{
+  svm_msg_q_ring_t *ring = svm_msg_q_get_ring (mq, msg->ring_index);
+  return svm_msg_q_ring_data (ring, msg->elt_index);
+}
+
+void
+svm_msg_q_free_msg (svm_msg_q_t * mq, svm_msg_q_msg_t * msg)
+{
+  svm_msg_q_ring_t *ring;
+
+  if (vec_len (mq->rings) <= msg->ring_index)
+    return;
+  ring = &mq->rings[msg->ring_index];
+  if (msg->elt_index == ring->head)
+    {
+      ring->head = (ring->head + 1) % ring->nitems;
+    }
+  else
+    {
+      /* for now, expect messages to be processed in order */
+      ASSERT (0);
+    }
+  __sync_fetch_and_sub (&ring->cursize, 1);
+}
+
+static int
+svm_msq_q_msg_is_valid (svm_msg_q_t * mq, svm_msg_q_msg_t * msg)
+{
+  svm_msg_q_ring_t *ring;
+  u32 dist1, dist2;
+
+  if (vec_len (mq->rings) <= msg->ring_index)
+    return 0;
+  ring = &mq->rings[msg->ring_index];
+
+  dist1 = ((ring->nitems + msg->ring_index) - ring->head) % ring->nitems;
+  if (ring->tail == ring->head)
+    dist2 = (ring->cursize == 0) ? 0 : ring->nitems;
+  else
+    dist2 = ((ring->nitems + ring->tail) - ring->head) % ring->nitems;
+  return (dist1 < dist2);
+}
+
+int
+svm_msg_q_add (svm_msg_q_t * mq, svm_msg_q_msg_t msg, int nowait)
+{
+  ASSERT (svm_msq_q_msg_is_valid (mq, &msg));
+  return svm_queue_add (mq->q, (u8 *) & msg, nowait);
+}
+
+int
+svm_msg_q_sub (svm_msg_q_t * mq, svm_msg_q_msg_t * msg,
+	       svm_q_conditional_wait_t cond, u32 time)
+{
+  return svm_queue_sub (mq->q, (u8 *) msg, cond, time);
+}
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */