vcl: set want deq flag earlier in epoll ctl mod

On epoll ctl mod, set want deq flag before checking if unhandled events
are needed.

Type: fix

Signed-off-by: Florin Coras <fcoras@cisco.com>
Change-Id: Id1491837c7156a66c21e0e45af60b04b1c18601c

Author: florincoras

src/vcl/vppcom.c

@@ -2929,6 +2929,15 @@ vppcom_epoll_ctl (uint32_t vep_handle, int op, uint32_t session_handle,
 	  goto done;
 	}
 
+      txf = vcl_session_is_ct (s) ? s->ct_tx_fifo : s->tx_fifo;
+      if (txf)
+	{
+	  if (event->events & EPOLLOUT)
+	    svm_fifo_add_want_deq_ntf (txf, SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL);
+	  else
+	    svm_fifo_del_want_deq_ntf (txf, SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL);
+	}
+
       /* Generate EPOLLOUT if session write ready nd event was not on */
       if ((event->events & EPOLLOUT) && !(s->vep.ev.events & EPOLLOUT) &&
 	  (vcl_session_write_ready (s) > 0))
@@ -2945,14 +2954,7 @@ vppcom_epoll_ctl (uint32_t vep_handle, int op, uint32_t session_handle,
 	}
       s->vep.et_mask = VEP_DEFAULT_ET_MASK;
       s->vep.ev = *event;
-      txf = vcl_session_is_ct (s) ? s->ct_tx_fifo : s->tx_fifo;
-      if (txf)
-	{
-	  if (event->events & EPOLLOUT)
-	    svm_fifo_add_want_deq_ntf (txf, SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL);
-	  else
-	    svm_fifo_del_want_deq_ntf (txf, SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL);
-	}
+
       VDBG (1, "EPOLL_CTL_MOD: vep_sh %u, sh %u, events 0x%x, data 0x%llx!",
 	    vep_handle, session_handle, event->events, event->data.u64);
       break;