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>

3 files changed, 9 insertions, 5 deletions

diff --git a/src/plugins/dpdk/device/cli.c b/src/plugins/dpdk/device/cli.c
index 765b298f8a9..04cf37f5304 100644
--- a/src/plugins/dpdk/device/cli.c
+++ b/src/plugins/dpdk/device/cli.c
@@ -1737,6 +1737,12 @@ VLIB_CLI_COMMAND (show_vpe_version_command, static) = {
 };
 /* *INDENT-ON* */
 
+/* Dummy function to get us linked in. */
+void
+dpdk_cli_reference (void)
+{
+}
+
 clib_error_t *
 dpdk_cli_init (vlib_main_t * vm)
 {
diff --git a/src/plugins/dpdk/device/dpdk.h b/src/plugins/dpdk/device/dpdk.h
index bd9b35901d5..f79465cf8b4 100644
--- a/src/plugins/dpdk/device/dpdk.h
+++ b/src/plugins/dpdk/device/dpdk.h
@@ -512,6 +512,7 @@ clib_error_t *unformat_hqos (unformat_input_t * input,
 
 struct rte_pci_device *dpdk_get_pci_device (const struct rte_eth_dev_info
 					    *info);
+void dpdk_cli_reference (void);
 
 #if CLI_DEBUG
 int dpdk_buffer_validate_trajectory_all (u32 * uninitialized);
diff --git a/src/plugins/dpdk/device/init.c b/src/plugins/dpdk/device/init.c
index c83b2b57c4c..22ea659094b 100644
--- a/src/plugins/dpdk/device/init.c
+++ b/src/plugins/dpdk/device/init.c
@@ -1734,6 +1734,8 @@ dpdk_init (vlib_main_t * vm)
   STATIC_ASSERT (RTE_CACHE_LINE_SIZE == 1 << CLIB_LOG2_CACHE_LINE_BYTES,
 		 "DPDK RTE CACHE LINE SIZE does not match with 1<<CLIB_LOG2_CACHE_LINE_BYTES");
 
+  dpdk_cli_reference ();
+
   dm->vlib_main = vm;
   dm->vnet_main = vnet_get_main ();
   dm->conf = &dpdk_config_main;
@@ -1751,10 +1753,6 @@ dpdk_init (vlib_main_t * vm)
   dm->stat_poll_interval = DPDK_STATS_POLL_INTERVAL;
   dm->link_state_poll_interval = DPDK_LINK_POLL_INTERVAL;
 
-  /* init CLI */
-  if ((error = vlib_call_init_function (vm, dpdk_cli_init)))
-    return error;
-
   dm->log_default = vlib_log_register_class ("dpdk", 0);
 
   return error;
@@ -1762,7 +1760,6 @@ dpdk_init (vlib_main_t * vm)
 
 VLIB_INIT_FUNCTION (dpdk_init);
 
-
 /*
  * fd.io coding-style-patch-verification: ON
  *