metrics: return error code on initialization failures

DPDK libraries should never call rte_exit on failure, so change the
function return type of rte_metrics_init to "int" to allow returning an
error code to the application rather than exiting the whole app on init
failure.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Morten Brørup <mb@smartsharesystems.com>

doc/guides/rel_notes/deprecation.rst

@@ -154,8 +154,5 @@ Deprecation Notices
   Event will be one of the configuration fields,
   together with additional vector parameters.
 
-* metrics: The function ``rte_metrics_init`` will have a non-void return
-  in order to notify errors instead of calling ``rte_exit``.
-
 * raw/dpaa2_cmdif: The ``dpaa2_cmdif`` rawdev driver will be deprecated
   in DPDK 22.11, as it is no longer in use, no active user known.

doc/guides/rel_notes/release_22_11.rst

@@ -247,6 +247,9 @@ API Changes
   and security capability structure ``rte_security_capability``
   to accommodate MACsec capabilities.
 
+* metrics: Updated ``rte_metrics_init`` so it returns an error code instead
+  of calling ``rte_exit``.
+
 * telemetry: The allowed characters in names for dictionary values
   are now limited to alphanumeric characters and a small subset of additional
   printable characters.

lib/metrics/rte_metrics.c

@@ -5,6 +5,7 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include <rte_errno.h>
 #include <rte_common.h>
 #include <rte_string_fns.h>
 #include <rte_metrics.h>
@@ -54,28 +55,29 @@ struct rte_metrics_data_s {
 	rte_spinlock_t lock;
 };
 
-void
+int
 rte_metrics_init(int socket_id)
 {
 	struct rte_metrics_data_s *stats;
 	const struct rte_memzone *memzone;
 
 	if (metrics_initialized)
-		return;
+		return 0;
 	if (rte_eal_process_type() != RTE_PROC_PRIMARY)
-		return;
+		return -E_RTE_SECONDARY;
 
 	memzone = rte_memzone_lookup(RTE_METRICS_MEMZONE_NAME);
 	if (memzone != NULL)
-		return;
+		return -EEXIST;
 	memzone = rte_memzone_reserve(RTE_METRICS_MEMZONE_NAME,
 		sizeof(struct rte_metrics_data_s), socket_id, 0);
 	if (memzone == NULL)
-		rte_exit(EXIT_FAILURE, "Unable to allocate stats memzone\n");
+		return -ENOMEM;
 	stats = memzone->addr;
 	memset(stats, 0, sizeof(struct rte_metrics_data_s));
 	rte_spinlock_init(&stats->lock);
 	metrics_initialized = 1;
+	return 0;
 }
 
 int

lib/metrics/rte_metrics.h

@@ -79,8 +79,14 @@ struct rte_metric_value {
  *
  * @param socket_id
  *   Socket to use for shared memory allocation.
+ * @return
+ *   0 on success
+ *   Negative error code (from rte_errno.h) on error:
+ *     -EEXIST - a memzone for metrics already exists but metrics is not initialized
+ *     -ENOMEM - cannot allocate metrics memzone
+ *     -E_RTE_SECONDARY - function called from secondary process
  */
-void rte_metrics_init(int socket_id);
+int rte_metrics_init(int socket_id);
 
 /**
  * Deinitialize metric module. This function must be called from