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, 7 deletions

diff --git a/src/plugins/tlsopenssl/tls_openssl.c b/src/plugins/tlsopenssl/tls_openssl.c
index f6de0e003e8..4d4c4c37170 100644
--- a/src/plugins/tlsopenssl/tls_openssl.c
+++ b/src/plugins/tlsopenssl/tls_openssl.c
@@ -835,14 +835,10 @@ tls_openssl_init (vlib_main_t * vm)
 {
   vlib_thread_main_t *vtm = vlib_get_thread_main ();
   openssl_main_t *om = &openssl_main;
-  clib_error_t *error;
   u32 num_threads;
 
   num_threads = 1 /* main thread */  + vtm->n_threads;
 
-  if ((error = vlib_call_init_function (vm, tls_init)))
-    return error;
-
   SSL_library_init ();
   SSL_load_error_strings ();
 
@@ -864,6 +860,12 @@ tls_openssl_init (vlib_main_t * vm)
 
   return 0;
 }
+/* *INDENT-OFF* */
+VLIB_INIT_FUNCTION (tls_openssl_init) =
+{
+  .runs_after = VLIB_INITS("tls_init"),
+};
+/* *INDENT-ON* */
 
 #ifdef HAVE_OPENSSL_ASYNC
 static clib_error_t *
@@ -938,9 +940,6 @@ VLIB_CLI_COMMAND (tls_openssl_set_command, static) =
 /* *INDENT-ON* */
 #endif
 
-
-VLIB_INIT_FUNCTION (tls_openssl_init);
-
 /* *INDENT-OFF* */
 VLIB_PLUGIN_REGISTER () = {
     .version = VPP_BUILD_VER,