vlib: Skip core 0 if workers are configured.

According to the description in the startup.conf, the assignment
of worker threads starts with the lcore following the main_lcore.
A non-zero skip_cores will correctly achieve this assignment.
However, prior to this patch when workers are assigned, the code
picks up and assigns core 0 even thought it shouldn't.
This patch determins if a non-zero number of workers are desired
and if so, marks CPU unavailable for a worker assignment.

Type: fix

Change-Id: I1fdf73a6f218dcbf146fda2efc90c553f7cd6d20
Signed-off-by: Jon Loeliger <jdl@netgate.com>
(cherry picked from commit 4a06846dd6)

src/vlib/threads.c

@@ -255,6 +255,21 @@ vlib_thread_init (vlib_main_t * vm)
     }
   avail_cpu = clib_bitmap_set (avail_cpu, tm->main_lcore, 0);
 
+  /*
+   * Determine if the number of workers is greater than 0.
+   * If so, mark CPU 0 unavailable so workers will be numbered after main.
+   */
+  u32 n_workers = 0;
+  uword *p = hash_get_mem (tm->thread_registrations_by_name, "workers");
+  if (p != 0)
+    {
+      vlib_thread_registration_t *tr = (vlib_thread_registration_t *) p[0];
+      int worker_thread_count = tr->count;
+      n_workers = worker_thread_count;
+    }
+  if (tm->skip_cores == 0 && n_workers)
+    avail_cpu = clib_bitmap_set (avail_cpu, 0, 0);
+
   /* assume that there is socket 0 only if there is no data from sysfs */
   if (!tm->cpu_socket_bitmap)
     tm->cpu_socket_bitmap = clib_bitmap_set (0, 0, 1);