monitor: unify global init

There are many places where the monitor initializes its globals:

- monitor_init_qmp_commands() at the very beginning
- single function to init monitor_lock
- in the first entry of monitor_init() using "is_first_init"

Unify them a bit.

monitor_lock is not used before monitor_init() (as confirmed by code
analysis and gdb watchpoints); so we are safe delaying what was a
constructor-time initialization of the mutex into the later first call
to monitor_init().

Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20180309090006.10018-8-peterx@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

include/monitor/monitor.h

@@ -16,7 +16,7 @@ extern Monitor *cur_mon;
 
 bool monitor_cur_is_qmp(void);
 
-void monitor_init_qmp_commands(void);
+void monitor_init_globals(void);
 void monitor_init(Chardev *chr, int flags);
 void monitor_cleanup(void);
 

monitor.c

@@ -1006,7 +1006,7 @@ static void qmp_unregister_commands_hack(void)
 #endif
 }
 
-void monitor_init_qmp_commands(void)
+static void monitor_init_qmp_commands(void)
 {
     /*
      * Two command lists:
@@ -3988,6 +3988,14 @@ static void sortcmdlist(void)
     qsort((void *)info_cmds, array_num, elem_size, compare_mon_cmd);
 }
 
+void monitor_init_globals(void)
+{
+    monitor_init_qmp_commands();
+    monitor_qapi_event_init();
+    sortcmdlist();
+    qemu_mutex_init(&monitor_lock);
+}
+
 /* These functions just adapt the readline interface in a typesafe way.  We
  * could cast function pointers but that discards compiler checks.
  */
@@ -4028,23 +4036,10 @@ void error_vprintf_unless_qmp(const char *fmt, va_list ap)
     }
 }
 
-static void __attribute__((constructor)) monitor_lock_init(void)
-{
-    qemu_mutex_init(&monitor_lock);
-}
-
 void monitor_init(Chardev *chr, int flags)
 {
-    static int is_first_init = 1;
-    Monitor *mon;
+    Monitor *mon = g_malloc(sizeof(*mon));
 
-    if (is_first_init) {
-        monitor_qapi_event_init();
-        sortcmdlist();
-        is_first_init = 0;
-    }
-
-    mon = g_malloc(sizeof(*mon));
     monitor_data_init(mon, false);
 
     qemu_chr_fe_init(&mon->chr, chr, &error_abort);

vl.c

@@ -3066,7 +3066,6 @@ int main(int argc, char **argv, char **envp)
     qemu_init_exec_dir(argv[0]);
 
     module_call_init(MODULE_INIT_QOM);
-    monitor_init_qmp_commands();
 
     qemu_add_opts(&qemu_drive_opts);
     qemu_add_drive_opts(&qemu_legacy_drive_opts);
@@ -4537,6 +4536,12 @@ int main(int argc, char **argv, char **envp)
     default_drive(default_floppy, snapshot, IF_FLOPPY, 0, FD_OPTS);
     default_drive(default_sdcard, snapshot, IF_SD, 0, SD_OPTS);
 
+    /*
+     * Note: qtest_enabled() (which is used in monitor_qapi_event_init())
+     * depends on configure_accelerator() above.
+     */
+    monitor_init_globals();
+
     if (qemu_opts_foreach(qemu_find_opts("mon"),
                           mon_init_func, NULL, NULL)) {
         exit(1);