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, 19 insertions, 16 deletions

diff --git a/src/vnet/ethernet/init.c b/src/vnet/ethernet/init.c
index 5d10c60fd5f..9fd95f1b75a 100644
--- a/src/vnet/ethernet/init.c
+++ b/src/vnet/ethernet/init.c
@@ -83,14 +83,6 @@ static clib_error_t *
 ethernet_init (vlib_main_t * vm)
 {
   ethernet_main_t *em = &ethernet_main;
-  clib_error_t *error;
-
-  /*
-   * Set up the L2 path now, or we'll wipe out the L2 ARP
-   * registration set up by ethernet_arp_init.
-   */
-  if ((error = vlib_call_init_function (vm, l2_init)))
-    return error;
 
   em->vlib_main = vm;
 
@@ -101,17 +93,28 @@ ethernet_init (vlib_main_t * vm)
 #include "types.def"
 #undef ethernet_type
 
-  if ((error = vlib_call_init_function (vm, llc_init)))
-    return error;
-  if ((error = vlib_call_init_function (vm, ethernet_input_init)))
-    return error;
-  if ((error = vlib_call_init_function (vm, vnet_feature_init)))
-    return error;
-
+  /*
+   * ethernet_input_init is effectively part of this function.
+   * Simply ensuring that it happens after we set up the hash tables
+   * is not sufficient.
+   */
+  ethernet_input_init (vm, em);
   return 0;
 }
 
-VLIB_INIT_FUNCTION (ethernet_init);
+/* *INDENT-OFF* */
+VLIB_INIT_FUNCTION (ethernet_init) =
+{
+  /*
+   * Set up the L2 path before ethernet_init, or we'll wipe out the L2 ARP
+   * registration set up by ethernet_arp_init.
+   */
+  .init_order = VLIB_INITS("l2_init",
+                           "ethernet_init",
+                           "llc_init",
+                           "vnet_feature_init"),
+};
+/* *INDENT-ON* */
 
 ethernet_main_t *
 ethernet_get_main (vlib_main_t * vm)