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/avf/device.c b/src/plugins/avf/device.c
index 7d01149a1a0..74b6ab4e4b0 100644
--- a/src/plugins/avf/device.c
+++ b/src/plugins/avf/device.c
@@ -1433,12 +1433,8 @@ clib_error_t *
 avf_init (vlib_main_t * vm)
 {
   avf_main_t *am = &avf_main;
-  clib_error_t *error;
   vlib_thread_main_t *tm = vlib_get_thread_main ();
 
-  if ((error = vlib_call_init_function (vm, pci_bus_init)))
-    return error;
-
   vec_validate_aligned (am->per_thread_data, tm->n_vlib_mains - 1,
 			CLIB_CACHE_LINE_BYTES);
 
@@ -1448,7 +1444,12 @@ avf_init (vlib_main_t * vm)
   return 0;
 }
 
-VLIB_INIT_FUNCTION (avf_init);
+/* *INDENT-OFF* */
+VLIB_INIT_FUNCTION (avf_init) =
+{
+  .runs_after = VLIB_INITS ("pci_bus_init"),
+};
+/* *INDENT-OFF* */
 
 /*
  * fd.io coding-style-patch-verification: ON