session svm: fix mq producer wait on q and ring

Make sure producer drops lock when it waits for empty ring slot.

Type: fix

Signed-off-by: Florin Coras <fcoras@cisco.com>
Change-Id: Id77d54ee8c01bed20c9eaf5ad372ed4b1e9fa712

2 files changed, 46 insertions, 5 deletions

diff --git a/src/svm/message_queue.c b/src/svm/message_queue.c
index a6af7962f73..2880645b427 100644
--- a/src/svm/message_queue.c
+++ b/src/svm/message_queue.c
@@ -243,8 +243,7 @@ svm_msg_q_lock_and_alloc_msg_w_ring (svm_msg_q_t * mq, u32 ring_index,
     {
       if (svm_msg_q_try_lock (mq))
 	return -1;
-      if (PREDICT_FALSE (svm_msg_q_is_full (mq)
-			 || svm_msg_q_ring_is_full (mq, ring_index)))
+      if (PREDICT_FALSE (svm_msg_q_or_ring_is_full (mq, ring_index)))
 	{
 	  svm_msg_q_unlock (mq);
 	  return -2;
@@ -254,9 +253,8 @@ svm_msg_q_lock_and_alloc_msg_w_ring (svm_msg_q_t * mq, u32 ring_index,
   else
     {
       svm_msg_q_lock (mq);
-      while (svm_msg_q_is_full (mq)
-	     || svm_msg_q_ring_is_full (mq, ring_index))
-	svm_msg_q_wait_prod (mq);
+      while (svm_msg_q_or_ring_is_full (mq, ring_index))
+	svm_msg_q_or_ring_wait_prod (mq, ring_index);
       *msg = svm_msg_q_alloc_msg_w_ring (mq, ring_index);
     }
   return 0;
@@ -569,6 +567,35 @@ svm_msg_q_wait_prod (svm_msg_q_t *mq)
 }
 
 int
+svm_msg_q_or_ring_wait_prod (svm_msg_q_t *mq, u32 ring_index)
+{
+  if (mq->q.evtfd == -1)
+    {
+      while (svm_msg_q_or_ring_is_full (mq, ring_index))
+	pthread_cond_wait (&mq->q.shr->condvar, &mq->q.shr->mutex);
+    }
+  else
+    {
+      u64 buf;
+      int rv;
+
+      while (svm_msg_q_or_ring_is_full (mq, ring_index))
+	{
+	  while ((rv = read (mq->q.evtfd, &buf, sizeof (buf))) < 0)
+	    {
+	      if (errno != EAGAIN)
+		{
+		  clib_unix_warning ("read error");
+		  return rv;
+		}
+	    }
+	}
+    }
+
+  return 0;
+}
+
+int
 svm_msg_q_timedwait (svm_msg_q_t *mq, double timeout)
 {
   if (mq->q.evtfd == -1)
diff --git a/src/svm/message_queue.h b/src/svm/message_queue.h
index bd76eda5d88..0780cca1c32 100644
--- a/src/svm/message_queue.h
+++ b/src/svm/message_queue.h
@@ -328,6 +328,12 @@ svm_msg_q_ring_is_full (svm_msg_q_t * mq, u32 ring_index)
   return (clib_atomic_load_relax_n (&ring->shr->cursize) >= ring->nitems);
 }
 
+static inline u8
+svm_msg_q_or_ring_is_full (svm_msg_q_t *mq, u32 ring_index)
+{
+  return (svm_msg_q_is_full (mq) || svm_msg_q_ring_is_full (mq, ring_index));
+}
+
 /**
  * Check if message queue is empty
  */
@@ -418,6 +424,14 @@ int svm_msg_q_wait (svm_msg_q_t *mq, svm_msg_q_wait_type_t type);
 int svm_msg_q_wait_prod (svm_msg_q_t *mq);
 
 /**
+ * Wait for message queue or ring event as producer
+ *
+ * Similar to @ref svm_msg_q_wait but lock (mutex or spinlock) must
+ * be held. Should only be called by producers.
+ */
+int svm_msg_q_or_ring_wait_prod (svm_msg_q_t *mq, u32 ring_index);
+
+/**
  * Timed wait for message queue event
  *
  * Must be called with mutex held.