From: Dave Barach <dave@barachs.net>
Date: Fri, 8 Nov 2019 13:22:28 +0000 (-0500)
Subject: vlib: fix handoff queue sequencing bug
X-Git-Tag: v20.05-rc0~403
X-Git-Url: https://gerrit.fd.io/r/gitweb?p=vpp.git;a=commitdiff_plain;h=320998a8126766c0db92d9c7652f765f9565a7b5

vlib: fix handoff queue sequencing bug

Set vm->check_frame_queues after actually enqueuing a frame. Under
obscure circumstances, the code managed to set check_frame_queues so
far in advance that 100 dispatch cycles could elapse before the frame
enqueue succeeded. That resulted in permanent lack of queue service.

Type: fix
Ticket: VPP-1734
Fixes: 18191

Signed-off-by: Dave Barach <dave@barachs.net>
Change-Id: If2d398202b4ba2b96581d25e8142daef3f74c9e5
---

diff --git a/src/vlib/buffer_node.h b/src/vlib/buffer_node.h
index 5ded5066563..96b50ae3551 100644
--- a/src/vlib/buffer_node.h
+++ b/src/vlib/buffer_node.h
@@ -517,7 +517,6 @@ vlib_buffer_enqueue_to_thread (vlib_main_t * vm, u32 frame_queue_index,
 	      n_drop++;
 	      goto next;
 	    }
-	  vlib_mains[next_thread_index]->check_frame_queues = 1;
 
 	  if (hf)
 	    hf->n_vectors = VLIB_FRAME_SIZE - n_left_to_next_thread;
@@ -539,6 +538,7 @@ vlib_buffer_enqueue_to_thread (vlib_main_t * vm, u32 frame_queue_index,
 	{
 	  hf->n_vectors = VLIB_FRAME_SIZE;
 	  vlib_put_frame_queue_elt (hf);
+	  vlib_mains[current_thread_index]->check_frame_queues = 1;
 	  current_thread_index = ~0;
 	  ptd->handoff_queue_elt_by_thread_index[next_thread_index] = 0;
 	  hf = 0;
@@ -567,6 +567,7 @@ vlib_buffer_enqueue_to_thread (vlib_main_t * vm, u32 frame_queue_index,
 	  if (1 || hf->n_vectors == hf->last_n_vectors)
 	    {
 	      vlib_put_frame_queue_elt (hf);
+	      vlib_mains[i]->check_frame_queues = 1;
 	      ptd->handoff_queue_elt_by_thread_index[i] = 0;
 	    }
 	  else