MINOR: init: add REGISTER_POST_DEINIT_MASTER() hook

Similar to REGISTER_POST_DEINIT() hook (which is invoked during deinit)
but for master process only, when haproxy was started in master-worker
mode. The goal is to be able to register cleanup functions that will
only run for the master process right before exiting.

include/haproxy/init.h

@@ -14,6 +14,7 @@ extern struct list post_server_check_list;
 extern struct list per_thread_alloc_list;
 extern struct list per_thread_init_list;
 extern struct list post_deinit_list;
+extern struct list post_deinit_master_list;
 extern struct list proxy_deinit_list;
 extern struct list server_deinit_list;
 extern struct list per_thread_free_list;
@@ -24,6 +25,7 @@ void hap_register_post_check(int (*fct)());
 void hap_register_post_proxy_check(int (*fct)(struct proxy *));
 void hap_register_post_server_check(int (*fct)(struct server *));
 void hap_register_post_deinit(void (*fct)());
+void hap_register_post_deinit_master(void (*fct)());
 void hap_register_proxy_deinit(void (*fct)(struct proxy *));
 void hap_register_server_deinit(void (*fct)(struct server *));
 
@@ -63,6 +65,10 @@ void hap_register_unittest(const char *name, int (*fct)(int, char **));
 #define REGISTER_POST_DEINIT(fct) \
 	INITCALL1(STG_REGISTER, hap_register_post_deinit, (fct))
 
+/* simplified way to declare a post-deinit (master process when launched in master/worker mode) callback in a file */
+#define REGISTER_POST_DEINIT_MASTER(fct) \
+	INITCALL1(STG_REGISTER, hap_register_post_deinit_master, (fct))
+
 /* simplified way to declare a proxy-deinit callback in a file */
 #define REGISTER_PROXY_DEINIT(fct) \
 	INITCALL1(STG_REGISTER, hap_register_proxy_deinit, (fct))

src/init.c

@@ -57,6 +57,11 @@ struct list per_thread_init_list = LIST_HEAD_INIT(per_thread_init_list);
  */
 struct list post_deinit_list = LIST_HEAD_INIT(post_deinit_list);
 
+/* These functions after everything is stopped, right before exit(), for the master
+ * process when haproxy was started in master-worker mode. They don't return anything.
+ */
+struct list post_deinit_master_list = LIST_HEAD_INIT(post_deinit_master_list);
+
 /* These functions are called when freeing a proxy during the deinit, after
  * everything isg stopped. They don't return anything. They should not release
  * the proxy itself or any shared resources that are possibly used by other
@@ -160,6 +165,22 @@ void hap_register_post_deinit(void (*fct)())
 	LIST_APPEND(&post_deinit_list, &b->list);
 }
 
+/* used to register some de-initialization functions to call after everything
+ * has stopped, but only for the master process (when started in master-worker mode).
+ */
+void hap_register_post_deinit_master(void (*fct)())
+{
+	struct post_deinit_fct *b;
+
+	b = calloc(1, sizeof(*b));
+	if (!b) {
+		fprintf(stderr, "out of memory\n");
+		exit(1);
+	}
+	b->fct = fct;
+	LIST_APPEND(&post_deinit_master_list, &b->list);
+}
+
 /* used to register some per proxy de-initialization functions to call after
  * everything has stopped.
  */

src/mworker.c

@@ -29,6 +29,7 @@
 #include <haproxy/list.h>
 #include <haproxy/log.h>
 #include <haproxy/listener.h>
+#include <haproxy/list.h>
 #include <haproxy/mworker.h>
 #include <haproxy/peers.h>
 #include <haproxy/proto_sockpair.h>
@@ -625,7 +626,13 @@ restart_wait:
 	}
 	/* Better rely on the system than on a list of process to check if it was the last one */
 	else if (exitpid == -1 && errno == ECHILD) {
+		struct post_deinit_fct *pdff;
+
 		ha_warning("All workers exited. Exiting... (%d)\n", (exitcode > 0) ? exitcode : EXIT_SUCCESS);
+
+		list_for_each_entry(pdff, &post_deinit_master_list, list)
+			pdff->fct();
+
 		atexit_flag = 0;
 		if (exitcode > 0)
 			exit(exitcode); /* parent must leave using the status code that provoked the exit */