2 files changed, 57 insertions, 2 deletions

diff --git a/src/svm/svm_fifo.c b/src/svm/svm_fifo.c
index 018827e0343..0c258b4259c 100644
--- a/src/svm/svm_fifo.c
+++ b/src/svm/svm_fifo.c
@@ -835,6 +835,53 @@ svm_fifo_dequeue_drop_all (svm_fifo_t * f)
   __sync_fetch_and_sub (&f->cursize, f->cursize);
 }
 
+int
+svm_fifo_segments (svm_fifo_t * f, svm_fifo_segment_t * fs)
+{
+  u32 cursize, nitems;
+
+  /* read cursize, which can only increase while we're working */
+  cursize = svm_fifo_max_dequeue (f);
+  if (PREDICT_FALSE (cursize == 0))
+    return -2;
+
+  nitems = f->nitems;
+
+  fs[0].len = ((nitems - f->head) < cursize) ? (nitems - f->head) : cursize;
+  fs[0].data = f->data + f->head;
+
+  if (fs[0].len < cursize)
+    {
+      fs[1].len = cursize - fs[0].len;
+      fs[1].data = f->data;
+    }
+  else
+    {
+      fs[1].len = 0;
+      fs[1].data = 0;
+    }
+  return cursize;
+}
+
+void
+svm_fifo_segments_free (svm_fifo_t * f, svm_fifo_segment_t * fs)
+{
+  u32 total_drop_bytes;
+
+  ASSERT (fs[0].data == f->data + f->head);
+  if (fs[1].len)
+    {
+      f->head = fs[1].len;
+      total_drop_bytes = fs[0].len + fs[1].len;
+    }
+  else
+    {
+      f->head = (f->head + fs[0].len) % f->nitems;
+      total_drop_bytes = fs[0].len;
+    }
+  __sync_fetch_and_sub (&f->cursize, total_drop_bytes);
+}
+
 u32
 svm_fifo_number_ooo_segments (svm_fifo_t * f)
 {
diff --git a/src/svm/svm_fifo.h b/src/svm/svm_fifo.h
index a8aea00996e..ec32fd5f40d 100644
--- a/src/svm/svm_fifo.h
+++ b/src/svm/svm_fifo.h
@@ -85,6 +85,12 @@ typedef enum
   SVM_FIFO_FULL = -2,
 } svm_fifo_err_t;
 
+typedef struct svm_fifo_segment_
+{
+  u8 *data;
+  u32 len;
+} svm_fifo_segment_t;
+
 #if SVM_FIFO_TRACE
 #define svm_fifo_trace_add(_f, _s, _l, _t)		\
 {							\
@@ -147,8 +153,8 @@ svm_fifo_has_ooo_data (svm_fifo_t * f)
 always_inline u8
 svm_fifo_set_event (svm_fifo_t * f)
 {
-//  return __sync_lock_test_and_set (&f->has_event, 1) == 0;
-//  return __sync_bool_compare_and_swap (&f->has_event, 0, 1);
+  /* return __sync_lock_test_and_set (&f->has_event, 1) == 0;
+     return __sync_bool_compare_and_swap (&f->has_event, 0, 1); */
   return !__atomic_exchange_n (&f->has_event, 1, __ATOMIC_RELEASE);
 }
 
@@ -175,6 +181,8 @@ int svm_fifo_dequeue_nowait (svm_fifo_t * f, u32 max_bytes, u8 * copy_here);
 int svm_fifo_peek (svm_fifo_t * f, u32 offset, u32 max_bytes, u8 * copy_here);
 int svm_fifo_dequeue_drop (svm_fifo_t * f, u32 max_bytes);
 void svm_fifo_dequeue_drop_all (svm_fifo_t * f);
+int svm_fifo_segments (svm_fifo_t * f, svm_fifo_segment_t * fs);
+void svm_fifo_segments_free (svm_fifo_t * f, svm_fifo_segment_t * fs);
 u32 svm_fifo_number_ooo_segments (svm_fifo_t * f);
 ooo_segment_t *svm_fifo_first_ooo_segment (svm_fifo_t * f);
 void svm_fifo_init_pointers (svm_fifo_t * f, u32 pointer);