Merge remote-tracking branch 'remotes/armbru/tags/pull-monitor-2018-10-30-v2' into staging

Monitor patches for 2018-10-30

# gpg: Signature made Tue 06 Nov 2018 17:37:16 GMT
# gpg:                using RSA key 3870B400EB918653
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>"
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>"
# Primary key fingerprint: 354B C8B3 D7EB 2A6B 6867  4E5F 3870 B400 EB91 8653

* remotes/armbru/tags/pull-monitor-2018-10-30-v2:
  vl: Avoid crash when -mon is underspecified
  monitor: delay monitor iothread creation
  monitor: guard iothread access by mon->use_io_thread
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

monitor.c

@@ -708,9 +708,14 @@ static void monitor_qapi_event_init(void)
 
 static void handle_hmp_command(Monitor *mon, const char *cmdline);
 
+static void monitor_iothread_init(void);
+
 static void monitor_data_init(Monitor *mon, bool skip_flush,
                               bool use_io_thread)
 {
+    if (use_io_thread && !mon_iothread) {
+        monitor_iothread_init();
+    }
     memset(mon, 0, sizeof(Monitor));
     qemu_mutex_init(&mon->mon_lock);
     qemu_mutex_init(&mon->qmp.qmp_queue_lock);
@@ -4292,7 +4297,7 @@ int monitor_suspend(Monitor *mon)
 
     atomic_inc(&mon->suspend_cnt);
 
-    if (monitor_is_qmp(mon)) {
+    if (monitor_is_qmp(mon) && mon->use_io_thread) {
         /*
          * Kick I/O thread to make sure this takes effect.  It'll be
          * evaluated again in prepare() of the watch object.
@@ -4461,15 +4466,6 @@ static AioContext *monitor_get_aio_context(void)
 static void monitor_iothread_init(void)
 {
     mon_iothread = iothread_create("mon_iothread", &error_abort);
-
-    /*
-     * The dispatcher BH must run in the main loop thread, since we
-     * have commands assuming that context.  It would be nice to get
-     * rid of those assumptions.
-     */
-    qmp_dispatcher_bh = aio_bh_new(iohandler_get_aio_context(),
-                                   monitor_qmp_bh_dispatcher,
-                                   NULL);
 }
 
 void monitor_init_globals(void)
@@ -4479,7 +4475,15 @@ void monitor_init_globals(void)
     sortcmdlist();
     qemu_mutex_init(&monitor_lock);
     qemu_mutex_init(&mon_fdsets_lock);
-    monitor_iothread_init();
+
+    /*
+     * The dispatcher BH must run in the main loop thread, since we
+     * have commands assuming that context.  It would be nice to get
+     * rid of those assumptions.
+     */
+    qmp_dispatcher_bh = aio_bh_new(iohandler_get_aio_context(),
+                                   monitor_qmp_bh_dispatcher,
+                                   NULL);
 }
 
 /* These functions just adapt the readline interface in a typesafe way.  We
@@ -4624,7 +4628,9 @@ void monitor_cleanup(void)
      * we need to unregister from chardev below in
      * monitor_data_destroy(), and chardev is not thread-safe yet
      */
-    iothread_stop(mon_iothread);
+    if (mon_iothread) {
+        iothread_stop(mon_iothread);
+    }
 
     /* Flush output buffers and destroy monitors */
     qemu_mutex_lock(&monitor_lock);
@@ -4639,9 +4645,10 @@ void monitor_cleanup(void)
     /* QEMUBHs needs to be deleted before destroying the I/O thread */
     qemu_bh_delete(qmp_dispatcher_bh);
     qmp_dispatcher_bh = NULL;
-
-    iothread_destroy(mon_iothread);
-    mon_iothread = NULL;
+    if (mon_iothread) {
+        iothread_destroy(mon_iothread);
+        mon_iothread = NULL;
+    }
 }
 
 QemuOptsList qemu_mon_opts = {

vl.c

@@ -2323,6 +2323,10 @@ static int mon_init_func(void *opaque, QemuOpts *opts, Error **errp)
     }
 
     chardev = qemu_opt_get(opts, "chardev");
+    if (!chardev) {
+        error_report("chardev is required");
+        exit(1);
+    }
     chr = qemu_chr_find(chardev);
     if (chr == NULL) {
         error_setg(errp, "chardev \"%s\" not found", chardev);