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, 14 insertions, 23 deletions

diff --git a/src/vnet/misc.c b/src/vnet/misc.c
index ff85e3dedfe..ab0f823cb65 100644
--- a/src/vnet/misc.c
+++ b/src/vnet/misc.c
@@ -74,31 +74,9 @@ clib_error_t *
 vnet_main_init (vlib_main_t * vm)
 {
   vnet_main_t *vnm = vnet_get_main ();
-  clib_error_t *error;
   u32 hw_if_index;
   vnet_hw_interface_t *hw;
 
-  if ((error = vlib_call_init_function (vm, vnet_interface_init)))
-    return error;
-
-  if ((error = vlib_call_init_function (vm, fib_module_init)))
-    return error;
-
-  if ((error = vlib_call_init_function (vm, mfib_module_init)))
-    return error;
-
-  if ((error = vlib_call_init_function (vm, ip_main_init)))
-    return error;
-
-  if ((error = vlib_call_init_function (vm, ip4_lookup_init)))
-    return error;
-
-  if ((error = vlib_call_init_function (vm, ip6_lookup_init)))
-    return error;
-
-  if ((error = vlib_call_init_function (vm, mpls_init)))
-    return error;
-
   vnm->vlib_main = vm;
 
   hw_if_index = vnet_register_interface
@@ -117,7 +95,20 @@ vnet_main_init (vlib_main_t * vm)
   return 0;
 }
 
-VLIB_INIT_FUNCTION (vnet_main_init);
+/* *INDENT-OFF* */
+VLIB_INIT_FUNCTION (vnet_main_init)=
+{
+  .init_order = VLIB_INITS("vnet_interface_init",
+                           "ethernet_init",
+                           "fib_module_init",
+                           "mfib_module_init",
+                           "ip_main_init",
+                           "ip4_lookup_init",
+                           "ip6_lookup_init",
+                           "mpls_init",
+                           "vnet_main_init"),
+};
+/* *INDENT-ON* */
 
 /*
  * fd.io coding-style-patch-verification: ON