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/devices/virtio/vhost_user.c b/src/vnet/devices/virtio/vhost_user.c
index 1d52b42b73b..72b71f98763 100644
--- a/src/vnet/devices/virtio/vhost_user.c
+++ b/src/vnet/devices/virtio/vhost_user.c
@@ -953,14 +953,9 @@ vhost_user_socksvr_accept_ready (clib_file_t * uf)
 static clib_error_t *
 vhost_user_init (vlib_main_t * vm)
 {
-  clib_error_t *error;
   vhost_user_main_t *vum = &vhost_user_main;
   vlib_thread_main_t *tm = vlib_get_thread_main ();
 
-  error = vlib_call_init_function (vm, ip4_init);
-  if (error)
-    return error;
-
   vum->log_default = vlib_log_register_class ("vhost-user", 0);
 
   vum->coalesce_frames = 32;
@@ -983,7 +978,12 @@ vhost_user_init (vlib_main_t * vm)
   return 0;
 }
 
-VLIB_INIT_FUNCTION (vhost_user_init);
+/* *INDENT-OFF* */
+VLIB_INIT_FUNCTION (vhost_user_init) =
+{
+  .runs_after = VLIB_INITS("ip4_init"),
+};
+/* *INDENT-ON* */
 
 static uword
 vhost_user_send_interrupt_process (vlib_main_t * vm,