svm: convert fifo want_deq_ntf ops to atomics

[vpp.git] / src / svm / svm_fifo.h

diff --git a/src/svm/svm_fifo.h b/src/svm/svm_fifo.h
index 42efb5a..7ea114f 100644 (file)
--- a/src/svm/svm_fifo.h
+++ b/src/svm/svm_fifo.h
@@ -35,8 +35,6 @@ typedef enum svm_fifo_deq_ntf_
   SVM_FIFO_WANT_DEQ_NOTIF = 1,         /**< Notify on dequeue */
   SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL = 2, /**< Notify on transition from full */
   SVM_FIFO_WANT_DEQ_NOTIF_IF_EMPTY = 4, /**< Notify on transition to empty */
-  SVM_FIFO_WANT_DEQ_NOTIF_IF_LEQ_THRESH = 5, /**< Notify on transition to less
-                                              than or equal threshold */
 } svm_fifo_deq_ntf_t;
 
 typedef enum svm_fifo_flag_
@@ -433,8 +431,8 @@ void svm_fifo_dequeue_drop_all (svm_fifo_t * f);
  * @param max_bytes    max bytes to be mapped to fifo segments
  * @return             number of bytes in fifo segments or SVM_FIFO_EEMPTY
  */
-int svm_fifo_segments (svm_fifo_t * f, u32 offset, svm_fifo_seg_t * fs,
-                      u32 n_segs, u32 max_bytes);
+int svm_fifo_segments (svm_fifo_t *f, u32 offset, svm_fifo_seg_t *fs,
+                      u32 *n_segs, u32 max_bytes);
 /**
  * Add io events subscriber to list
  *
@@ -761,7 +759,7 @@ svm_fifo_unset_event (svm_fifo_t * f)
 static inline void
 svm_fifo_add_want_deq_ntf (svm_fifo_t * f, u8 ntf_type)
 {
-  f->shr->want_deq_ntf |= ntf_type;
+  __atomic_or_fetch (&f->shr->want_deq_ntf, ntf_type, __ATOMIC_RELEASE);
 }
 
 /**
@@ -775,7 +773,21 @@ svm_fifo_add_want_deq_ntf (svm_fifo_t * f, u8 ntf_type)
 static inline void
 svm_fifo_del_want_deq_ntf (svm_fifo_t * f, u8 ntf_type)
 {
-  f->shr->want_deq_ntf &= ~ntf_type;
+  __atomic_and_fetch (&f->shr->want_deq_ntf, ~ntf_type, __ATOMIC_RELEASE);
+}
+
+/**
+ * Get want notification flag
+ *
+ * Done atomically with acquire memory ordering
+ *
+ * @param f    fifo
+ * @return     value of want_deq_ntf flag
+ */
+static inline u32
+svm_fifo_get_want_deq_ntf (svm_fifo_t *f)
+{
+  return clib_atomic_load_acq_n (&f->shr->want_deq_ntf);
 }
 
 /**
@@ -792,11 +804,27 @@ svm_fifo_del_want_deq_ntf (svm_fifo_t * f, u8 ntf_type)
 static inline void
 svm_fifo_clear_deq_ntf (svm_fifo_t * f)
 {
-  /* Set the flag if want_notif_if_full was the only ntf requested */
-  f->shr->has_deq_ntf =
-    f->shr->want_deq_ntf == SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL;
-  svm_fifo_del_want_deq_ntf (f, SVM_FIFO_WANT_DEQ_NOTIF |
-                                 SVM_FIFO_WANT_DEQ_NOTIF_IF_LEQ_THRESH);
+  u32 want_deq_ntf = svm_fifo_get_want_deq_ntf (f);
+  /* Set the flag if want ntf if full or empty was requested */
+  if (want_deq_ntf &
+      (SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL | SVM_FIFO_WANT_DEQ_NOTIF_IF_EMPTY))
+    clib_atomic_store_rel_n (&f->shr->has_deq_ntf, 1);
+  if (want_deq_ntf & SVM_FIFO_WANT_DEQ_NOTIF)
+    svm_fifo_del_want_deq_ntf (f, SVM_FIFO_WANT_DEQ_NOTIF);
+}
+
+/**
+ * Get has dequeue notification flag
+ *
+ * Done atomically with acquire memory ordering
+ *
+ * @param f    fifo
+ * @return     has_deq_ntf flag
+ */
+static inline u32
+svm_fifo_has_deq_ntf (svm_fifo_t *f)
+{
+  return clib_atomic_load_acq_n (&f->shr->has_deq_ntf);
 }
 
 /**
@@ -827,29 +855,23 @@ svm_fifo_reset_has_deq_ntf (svm_fifo_t * f)
 static inline u8
 svm_fifo_needs_deq_ntf (svm_fifo_t * f, u32 n_last_deq)
 {
-  u8 want_ntf = f->shr->want_deq_ntf;
+  u32 want_ntf = svm_fifo_get_want_deq_ntf (f);
 
-  if (PREDICT_TRUE (want_ntf == SVM_FIFO_NO_DEQ_NOTIF))
+  if (want_ntf == SVM_FIFO_NO_DEQ_NOTIF)
     return 0;
   else if (want_ntf & SVM_FIFO_WANT_DEQ_NOTIF)
-    return 1;
+    return (svm_fifo_max_enqueue (f) >= f->shr->deq_thresh);
   if (want_ntf & SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL)
     {
       u32 max_deq = svm_fifo_max_dequeue_cons (f);
       u32 size = f->shr->size;
-      if (!f->shr->has_deq_ntf && max_deq < size &&
-         max_deq + n_last_deq >= size)
+      if (max_deq < size && max_deq + n_last_deq >= size &&
+         !svm_fifo_has_deq_ntf (f))
        return 1;
     }
   if (want_ntf & SVM_FIFO_WANT_DEQ_NOTIF_IF_EMPTY)
     {
-      if (!f->shr->has_deq_ntf && svm_fifo_is_empty (f))
-       return 1;
-    }
-  if (want_ntf & SVM_FIFO_WANT_DEQ_NOTIF_IF_LEQ_THRESH)
-    {
-      if (!f->shr->has_deq_ntf &&
-         (svm_fifo_max_dequeue (f) <= f->shr->deq_thresh))
+      if (!svm_fifo_has_deq_ntf (f) && svm_fifo_is_empty (f))
        return 1;
     }
   return 0;
@@ -859,7 +881,7 @@ svm_fifo_needs_deq_ntf (svm_fifo_t * f, u32 n_last_deq)
  * Set the fifo dequeue threshold which will be used for notifications.
  *
  * Note: If not set, by default threshold is zero, equivalent to
- * empty.
+ * generating notification on each dequeue event.
  */
 static inline void
 svm_fifo_set_deq_thresh (svm_fifo_t *f, u32 thresh)