init / exit function ordering

The vlib init function subsystem now supports a mix of procedural and
formally-specified ordering constraints. We should eliminate procedural
knowledge wherever possible.

The following schemes are *roughly* equivalent:

static clib_error_t *init_runs_first (vlib_main_t *vm)
{
   clib_error_t *error;

   ... do some stuff...

   if ((error = vlib_call_init_function (init_runs_next)))
     return error;
   ...
}
VLIB_INIT_FUNCTION (init_runs_first);

and

static clib_error_t *init_runs_first (vlib_main_t *vm)
{
   ... do some stuff...
}
VLIB_INIT_FUNCTION (init_runs_first) =
{
    .runs_before = VLIB_INITS("init_runs_next"),
};

The first form will [most likely] call "init_runs_next" on the
spot. The second form means that "init_runs_first" runs before
"init_runs_next," possibly much earlier in the sequence.

Please DO NOT construct sets of init functions where A before B
actually means A *right before* B. It's not necessary - simply combine
A and B - and it leads to hugely annoying debugging exercises when
trying to switch from ad-hoc procedural ordering constraints to formal
ordering constraints.

Change-Id: I5e4353503bf43b4acb11a45fb33c79a5ade8426c
Signed-off-by: Dave Barach <dave@barachs.net>

1 files changed, 6 insertions, 5 deletions

diff --git a/src/plugins/cdp/cdp_input.c b/src/plugins/cdp/cdp_input.c
index 946aaf7f845..dbe179ad095 100644
--- a/src/plugins/cdp/cdp_input.c
+++ b/src/plugins/cdp/cdp_input.c
@@ -408,15 +408,11 @@ cdp_input (vlib_main_t * vm, vlib_buffer_t * b0, u32 bi0)
 static clib_error_t *
 cdp_input_init (vlib_main_t * vm)
 {
-  clib_error_t *error;
   cdp_main_t *cm = &cdp_main;
   void vnet_cdp_node_reference (void);
 
   vnet_cdp_node_reference ();
 
-  if ((error = vlib_call_init_function (vm, cdp_periodic_init)))
-    return error;
-
   cm->vlib_main = vm;
   cm->vnet_main = vnet_get_main ();
   cm->neighbor_by_sw_if_index = hash_create (0, sizeof (uword));
@@ -424,7 +420,12 @@ cdp_input_init (vlib_main_t * vm)
   return 0;
 }
 
-VLIB_INIT_FUNCTION (cdp_input_init);
+/* *INDENT-OFF* */
+VLIB_INIT_FUNCTION (cdp_input_init) =
+{
+  .runs_after = VLIB_INITS("cdp_periodic_init"),
+};
+/* *INDENT-ON* */
 
 
 static u8 *