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, 6 deletions

diff --git a/src/vnet/ethernet/arp.c b/src/vnet/ethernet/arp.c
index 12c3fa47eac..f294893d846 100644
--- a/src/vnet/ethernet/arp.c
+++ b/src/vnet/ethernet/arp.c
@@ -1761,12 +1761,8 @@ ethernet_arp_init (vlib_main_t * vm)
 {
   ethernet_arp_main_t *am = &ethernet_arp_main;
   ip4_main_t *im = &ip4_main;
-  clib_error_t *error;
   pg_node_t *pn;
 
-  if ((error = vlib_call_init_function (vm, ethernet_init)))
-    return error;
-
   ethernet_register_input_type (vm, ETHERNET_TYPE_ARP, arp_input_node.index);
 
   pn = pg_get_node (arp_input_node.index);
@@ -1809,8 +1805,12 @@ ethernet_arp_init (vlib_main_t * vm)
 
   return 0;
 }
-
-VLIB_INIT_FUNCTION (ethernet_arp_init);
+/* *INDENT-OFF* */
+VLIB_INIT_FUNCTION (ethernet_arp_init) =
+{
+  .runs_after = VLIB_INITS("ethernet_init"),
+};
+/* *INDENT-ON* */
 
 static void
 arp_entry_free (ethernet_arp_interface_t * eai, ethernet_arp_ip4_entry_t * e)