svm: fix multi-chunk fifo alloc and add more tests

Type: fix

- make sure that chunks and the rbtree are initialized if fifo segment
allocates multiple chunks for the fifo.
- ensure head/tail chunks are updated on all enqueue/dequeue events,
including when dropping data.
- more unit tests

Also fixes dequeue drop updates of head chunk.

Change-Id: I77f3550bc4e8b4e077f80ea87fe82b83ed013aeb
Signed-off-by: Florin Coras <fcoras@cisco.com>

1 files changed, 97 insertions, 6 deletions

diff --git a/src/svm/svm_fifo.c b/src/svm/svm_fifo.c
index 3d538293c70..56f53a3d339 100644
--- a/src/svm/svm_fifo.c
+++ b/src/svm/svm_fifo.c
@@ -404,6 +404,31 @@ svm_fifo_init (svm_fifo_t * f, u32 size)
   f->head_chunk = f->tail_chunk = f->ooo_enq = f->ooo_deq = f->start_chunk;
 }
 
+void
+svm_fifo_init_chunks (svm_fifo_t * f)
+{
+  svm_fifo_chunk_t *c, *prev;
+
+  if (f->start_chunk->next == f->start_chunk)
+    return;
+
+  f->flags |= SVM_FIFO_F_MULTI_CHUNK;
+  rb_tree_init (&f->chunk_lookup);
+  rb_tree_add2 (&f->chunk_lookup, 0, pointer_to_uword (f->start_chunk));
+
+  f->start_chunk->start_byte = 0;
+  prev = f->start_chunk;
+  c = prev->next;
+
+  while (c != f->start_chunk)
+    {
+      c->start_byte = prev->start_byte + prev->length;
+      rb_tree_add2 (&f->chunk_lookup, c->start_byte, pointer_to_uword (c));
+      prev = c;
+      c = c->next;
+    }
+}
+
 /**
  * Creates a fifo in the current heap. Fails vs blow up the process
  */
@@ -559,6 +584,7 @@ svm_fifo_add_chunk (svm_fifo_t * f, svm_fifo_chunk_t * c)
    * that this is called with the heap where the rbtree's pool is pushed. */
   if (!(f->flags & SVM_FIFO_F_MULTI_CHUNK))
     {
+      ASSERT (f->start_chunk->next == f->start_chunk);
       rb_tree_init (&f->chunk_lookup);
       rb_tree_add2 (&f->chunk_lookup, 0, pointer_to_uword (f->start_chunk));
       f->flags |= SVM_FIFO_F_MULTI_CHUNK;
@@ -626,7 +652,7 @@ svm_fifo_collect_chunks (svm_fifo_t * f)
 void
 svm_fifo_try_shrink (svm_fifo_t * f, u32 head, u32 tail)
 {
-  u32 len_to_shrink = 0, tail_pos, len;
+  u32 len_to_shrink = 0, tail_pos, len, last_pos;
   svm_fifo_chunk_t *cur, *prev, *next, *start;
 
   tail_pos = tail;
@@ -649,13 +675,24 @@ svm_fifo_try_shrink (svm_fifo_t * f, u32 head, u32 tail)
    * - not wrapped
    * - last used byte less than start of last chunk
    */
-  if (tail_pos >= head && tail_pos <= f->end_chunk->start_byte)
+  if (tail_pos >= head && tail_pos < f->end_chunk->start_byte)
     {
       /* Lookup the last position not to be removed. Since size still needs
-       * to be nitems + 1, nitems must fall within the usable space */
-      tail_pos = tail_pos > 0 ? tail_pos - 1 : tail_pos;
-      prev = svm_fifo_find_chunk (f, clib_max (f->nitems, tail_pos));
+       * to be nitems + 1, nitems must fall within the usable space. Also,
+       * first segment is not removable, so tail_pos can be 0. */
+      last_pos = tail_pos > 0 ? tail_pos - 1 : tail_pos;
+      prev = svm_fifo_find_chunk (f, clib_max (f->nitems, last_pos));
       next = prev->next;
+      /* If tail_pos is first position in next, skip the chunk, otherwise,
+       * we must update the tail and, if fifo size is 0, even the head.
+       * We should not invalidate the tail for the caller and must not change
+       * consumer owned variables from code that's typically called by the
+       * producer */
+      if (next->start_byte == tail_pos)
+	{
+	  prev = next;
+	  next = next->next;
+	}
       while (next != f->start_chunk)
 	{
 	  cur = next;
@@ -790,7 +827,11 @@ svm_fifo_enqueue (svm_fifo_t * f, u32 len, const u8 * src)
 
   /* collect out-of-order segments */
   if (PREDICT_FALSE (f->ooos_list_head != OOO_SEGMENT_INVALID_INDEX))
-    len += ooo_segment_try_collect (f, len, &tail);
+    {
+      len += ooo_segment_try_collect (f, len, &tail);
+      if (!svm_fifo_chunk_includes_pos (f->tail_chunk, tail))
+	f->tail_chunk = svm_fifo_find_chunk (f, tail);
+    }
 
   /* store-rel: producer owned index (paired with load-acq in consumer) */
   clib_atomic_store_rel_n (&f->tail, tail);
@@ -847,6 +888,10 @@ svm_fifo_enqueue_nocopy (svm_fifo_t * f, u32 len)
   /* load-relaxed: producer owned index */
   tail = f->tail;
   tail = (tail + len) % f->size;
+
+  if (!svm_fifo_chunk_includes_pos (f->tail_chunk, tail))
+    f->tail_chunk = svm_fifo_find_chunk (f, tail);
+
   /* store-rel: producer owned index (paired with load-acq in consumer) */
   clib_atomic_store_rel_n (&f->tail, tail);
 }
@@ -919,6 +964,9 @@ svm_fifo_dequeue_drop (svm_fifo_t * f, u32 len)
   /* move head */
   head = (head + total_drop_bytes) % f->size;
 
+  if (!svm_fifo_chunk_includes_pos (f->head_chunk, head))
+    f->head_chunk = svm_fifo_find_chunk (f, head);
+
   /* store-rel: consumer owned index (paired with load-acq in producer) */
   clib_atomic_store_rel_n (&f->head, head);
 
@@ -930,6 +978,10 @@ svm_fifo_dequeue_drop_all (svm_fifo_t * f)
 {
   /* consumer foreign index */
   u32 tail = clib_atomic_load_acq_n (&f->tail);
+
+  if (!svm_fifo_chunk_includes_pos (f->head_chunk, tail))
+    f->head_chunk = svm_fifo_find_chunk (f, tail);
+
   /* store-rel: consumer owned index (paired with load-acq in producer) */
   clib_atomic_store_rel_n (&f->head, tail);
 }
@@ -1055,6 +1107,45 @@ svm_fifo_del_subscriber (svm_fifo_t * f, u8 subscriber)
     }
 }
 
+u8
+svm_fifo_is_sane (svm_fifo_t * f)
+{
+  if (f->size - 1 != f->nitems && !(f->flags & SVM_FIFO_F_SHRINK))
+    return 0;
+  if (!svm_fifo_chunk_includes_pos (f->head_chunk, f->head))
+    return 0;
+  if (!svm_fifo_chunk_includes_pos (f->tail_chunk, f->tail))
+    return 0;
+
+  if (f->start_chunk->next != f->start_chunk)
+    {
+      svm_fifo_chunk_t *c, *prev = 0, *tmp;
+      u32 size = 0;
+
+      if (!(f->flags & SVM_FIFO_F_MULTI_CHUNK))
+	return 0;
+
+      c = f->start_chunk;
+      do
+	{
+	  tmp = svm_fifo_find_chunk (f, c->start_byte);
+	  if (tmp != c)
+	    return 0;
+	  if (prev && (prev->start_byte + prev->length != c->start_byte))
+	    return 0;
+	  size += c->length;
+	  prev = c;
+	  c = c->next;
+	}
+      while (c != f->start_chunk);
+
+      if (size != f->size)
+	return 0;
+    }
+
+  return 1;
+}
+
 u8 *
 format_ooo_segment (u8 * s, va_list * args)
 {