Monitor: Return before exiting with 'quit'

The 'quit' Monitor command (implemented by do_quit()) calls
exit() directly, this is problematic under QMP because QEMU
exits before having a chance to send the ok response.

Clients don't know if QEMU exited because of a problem or
because the 'quit' command has been executed.

This commit fixes that by moving the exit() call to the main
loop, so that do_quit() requests the system to quit, instead
of calling exit() directly.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>

monitor.c

@@ -1017,7 +1017,8 @@ static void do_info_cpu_stats(Monitor *mon)
  */
 static int do_quit(Monitor *mon, const QDict *qdict, QObject **ret_data)
 {
-    exit(0);
+    monitor_suspend(mon);
+    qemu_system_exit_request();
     return 0;
 }
 

sysemu.h

@@ -45,9 +45,11 @@ void cpu_disable_ticks(void);
 void qemu_system_reset_request(void);
 void qemu_system_shutdown_request(void);
 void qemu_system_powerdown_request(void);
+void qemu_system_exit_request(void);
 int qemu_shutdown_requested(void);
 int qemu_reset_requested(void);
 int qemu_powerdown_requested(void);
+int qemu_exit_requested(void);
 extern qemu_irq qemu_system_powerdown;
 void qemu_system_reset(void);
 

vl.c

@@ -1697,6 +1697,7 @@ static int shutdown_requested;
 static int powerdown_requested;
 int debug_requested;
 int vmstop_requested;
+static int exit_requested;
 
 int qemu_shutdown_requested(void)
 {
@@ -1719,6 +1720,12 @@ int qemu_powerdown_requested(void)
     return r;
 }
 
+int qemu_exit_requested(void)
+{
+    /* just return it, we'll exit() anyway */
+    return exit_requested;
+}
+
 static int qemu_debug_requested(void)
 {
     int r = debug_requested;
@@ -1789,6 +1796,12 @@ void qemu_system_powerdown_request(void)
     qemu_notify_event();
 }
 
+void qemu_system_exit_request(void)
+{
+    exit_requested = 1;
+    qemu_notify_event();
+}
+
 #ifdef _WIN32
 static void host_main_loop_wait(int *timeout)
 {
@@ -1925,6 +1938,8 @@ static int vm_can_run(void)
         return 0;
     if (debug_requested)
         return 0;
+    if (exit_requested)
+        return 0;
     return 1;
 }
 
@@ -1977,6 +1992,9 @@ static void main_loop(void)
         if ((r = qemu_vmstop_requested())) {
             vm_stop(r);
         }
+        if (qemu_exit_requested()) {
+            exit(0);
+        }
     }
     pause_all_vcpus();
 }