[Qemu-devel] [RFC 1/5] ui/cocoa: Ensure we have the iothread lock when calling into QEMU

[Peter Maydell]

The Cocoa UI should run on the main thread; this is enforced
in OSX Mojave. In order to be able to run on the main thread,
we need to make sure we hold the iothread lock whenever we
call into various QEMU UI midlayer functions.

Signed-off-by: Peter Maydell <address@hidden>
---
 ui/cocoa.m | 83 ++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 59 insertions(+), 24 deletions(-)

diff --git a/ui/cocoa.m b/ui/cocoa.m
index ecf12bfc2e4..9148ecdeb4c 100644
--- a/ui/cocoa.m
+++ b/ui/cocoa.m
@@ -117,6 +117,21 @@ bool stretch_video;
 NSTextField *pauseLabel;
 NSArray * supportedImageFileTypes;
 
+// Utility function to run specified code block with iothread lock held
+typedef void (^CodeBlock)(void);
+
+static void with_iothread_lock(CodeBlock block)
+{
+    bool locked = qemu_mutex_iothread_locked();
+    if (!locked) {
+        qemu_mutex_lock_iothread();
+    }
+    block();
+    if (!locked) {
+        qemu_mutex_unlock_iothread();
+    }
+}
+
 // Mac to QKeyCode conversion
 const int mac_to_qkeycode_map[] = {
     [kVK_ANSI_A] = Q_KEY_CODE_A,
@@ -294,6 +309,7 @@ static void handleAnyDeviceErrors(Error * err)
 - (void) toggleFullScreen:(id)sender;
 - (void) handleMonitorInput:(NSEvent *)event;
 - (void) handleEvent:(NSEvent *)event;
+- (void) handleEventLocked:(NSEvent *)event;
 - (void) setAbsoluteEnabled:(BOOL)tIsAbsoluteEnabled;
 /* The state surrounding mouse grabbing is potentially confusing.
  * isAbsoluteEnabled tracks qemu_input_is_absolute() [ie "is the emulated
@@ -632,8 +648,14 @@ QemuCocoaView *cocoaView;
 
 - (void) handleEvent:(NSEvent *)event
 {
-    COCOA_DEBUG("QemuCocoaView: handleEvent\n");
+    with_iothread_lock(^{
+        [self handleEventLocked:event];
+    });
+}
 
+- (void) handleEventLocked:(NSEvent *)event
+{
+    COCOA_DEBUG("QemuCocoaView: handleEvent\n");
     int buttons = 0;
     int keycode = 0;
     bool mouse_event = false;
@@ -928,15 +950,18 @@ QemuCocoaView *cocoaView;
  */
 - (void) raiseAllKeys
 {
-    int index;
     const int max_index = ARRAY_SIZE(modifiers_state);
 
-   for (index = 0; index < max_index; index++) {
-       if (modifiers_state[index]) {
-           modifiers_state[index] = 0;
-           qemu_input_event_send_key_qcode(dcl->con, index, false);
-       }
-   }
+    with_iothread_lock(^{
+        int index;
+
+        for (index = 0; index < max_index; index++) {
+            if (modifiers_state[index]) {
+                modifiers_state[index] = 0;
+                qemu_input_event_send_key_qcode(dcl->con, index, false);
+            }
+        }
+    });
 }
 @end
 
@@ -1198,13 +1223,17 @@ QemuCocoaView *cocoaView;
 /* Restarts QEMU */
 - (void)restartQEMU:(id)sender
 {
-    qmp_system_reset(NULL);
+    with_iothread_lock(^{
+        qmp_system_reset(NULL);
+    });
 }
 
 /* Powers down QEMU */
 - (void)powerDownQEMU:(id)sender
 {
-    qmp_system_powerdown(NULL);
+    with_iothread_lock(^{
+        qmp_system_powerdown(NULL);
+    });
 }
 
 /* Ejects the media.
@@ -1220,9 +1249,11 @@ QemuCocoaView *cocoaView;
         return;
     }
 
-    Error *err = NULL;
-    qmp_eject(true, [drive cStringUsingEncoding: NSASCIIStringEncoding],
-              false, NULL, false, false, &err);
+    __block Error *err = NULL;
+    with_iothread_lock(^{
+        qmp_eject(true, [drive cStringUsingEncoding: NSASCIIStringEncoding],
+                  false, NULL, false, false, &err);
+    });
     handleAnyDeviceErrors(err);
 }
 
@@ -1254,16 +1285,18 @@ QemuCocoaView *cocoaView;
             return;
         }
 
-        Error *err = NULL;
-        qmp_blockdev_change_medium(true,
-                                   [drive cStringUsingEncoding:
-                                          NSASCIIStringEncoding],
-                                   false, NULL,
-                                   [file cStringUsingEncoding:
-                                         NSASCIIStringEncoding],
-                                   true, "raw",
-                                   false, 0,
-                                   &err);
+        __block Error *err = NULL;
+        with_iothread_lock(^{
+            qmp_blockdev_change_medium(true,
+                                       [drive cStringUsingEncoding:
+                                                  NSASCIIStringEncoding],
+                                       false, NULL,
+                                       [file cStringUsingEncoding:
+                                                 NSASCIIStringEncoding],
+                                       true, "raw",
+                                       false, 0,
+                                       &err);
+        });
         handleAnyDeviceErrors(err);
     }
 }
@@ -1402,7 +1435,9 @@ QemuCocoaView *cocoaView;
     // get the throttle percentage
     throttle_pct = [sender tag];
 
-    cpu_throttle_set(throttle_pct);
+    with_iothread_lock(^{
+        cpu_throttle_set(throttle_pct);
+    });
     COCOA_DEBUG("cpu throttling at %d%c\n", cpu_throttle_get_percentage(), 
'%');
 }
 
-- 
2.19.2