virtio: fix txq locking

Initialize txq lock only if some txq are shared and check if another
worker is already operating on the txq before processing gro timeouts
in input node.

Type: fix

Change-Id: I89dab6c0e6eb6a7aa621fa1548b0a2c76e6c7581
Signed-off-by: Benoît Ganne <bganne@cisco.com>
(cherry picked from commit b6b484d01a)

src/vnet/devices/virtio/node.c

@@ -279,10 +279,12 @@ virtio_device_input_gso_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
   u16 last = vring->last_used_idx;
   u16 n_left = vring->used->idx - last;
 
-  if (vif->packet_coalesce)
+  if (vif->packet_coalesce
+      && clib_spinlock_trylock_if_init (&txq_vring->lockp))
     {
       vnet_gro_flow_table_schedule_node_on_dispatcher (vm,
 						       txq_vring->flow_table);
+      clib_spinlock_unlock_if_init (&txq_vring->lockp);
     }
 
   if ((vring->used->flags & VRING_USED_F_NO_NOTIFY) == 0 &&

src/vnet/devices/virtio/pci.c

@@ -494,6 +494,7 @@ virtio_pci_control_vring_init (vlib_main_t * vm, virtio_if_t * vif,
 clib_error_t *
 virtio_pci_vring_init (vlib_main_t * vm, virtio_if_t * vif, u16 queue_num)
 {
+  vlib_thread_main_t *vtm = vlib_get_thread_main ();
   clib_error_t *error = 0;
   u16 queue_size = 0;
   virtio_vring_t *vring;
@@ -519,6 +520,7 @@ virtio_pci_vring_init (vlib_main_t * vm, virtio_if_t * vif, u16 queue_num)
       vec_validate_aligned (vif->txq_vrings, TX_QUEUE_ACCESS (queue_num),
 			    CLIB_CACHE_LINE_BYTES);
       vring = vec_elt_at_index (vif->txq_vrings, TX_QUEUE_ACCESS (queue_num));
+      if (vif->max_queue_pairs < vtm->n_vlib_mains)
 	clib_spinlock_init (&vring->lockp);
     }
   else

src/vppinfra/lock.h

@@ -91,6 +91,15 @@ clib_spinlock_lock (clib_spinlock_t * p)
   CLIB_LOCK_DBG (p);
 }
 
+static_always_inline int
+clib_spinlock_trylock (clib_spinlock_t * p)
+{
+  if (PREDICT_FALSE (CLIB_SPINLOCK_IS_LOCKED (p)))
+    return 0;
+  clib_spinlock_lock (p);
+  return 1;
+}
+
 static_always_inline void
 clib_spinlock_lock_if_init (clib_spinlock_t * p)
 {
@@ -98,6 +107,14 @@ clib_spinlock_lock_if_init (clib_spinlock_t * p)
     clib_spinlock_lock (p);
 }
 
+static_always_inline int
+clib_spinlock_trylock_if_init (clib_spinlock_t * p)
+{
+  if (PREDICT_FALSE (*p != 0))
+    return clib_spinlock_trylock (p);
+  return 1;
+}
+
 static_always_inline void
 clib_spinlock_unlock (clib_spinlock_t * p)
 {