Merge remote-tracking branch 'remotes/kraxel/tags/ui-20201104-pull-request' into staging

ui: run screendump in coroutine

# gpg: Signature made Wed 04 Nov 2020 13:53:50 GMT
# gpg:                using RSA key 4CB6D8EED3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>" [full]
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>" [full]
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>" [full]
# Primary key fingerprint: A032 8CFF B93A 17A7 9901  FE7D 4CB6 D8EE D3E8 7138

* remotes/kraxel/tags/ui-20201104-pull-request:
  console: make QMP/HMP screendump run in coroutine
  console: modify ppm_save to take a pixman image ref
  coroutine: let CoQueue wake up outside a coroutine

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

6 files changed, 45 insertions, 17 deletions

diff --git a/hmp-commands.hx b/hmp-commands.hx
index cd06838..ff2d7aa 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -254,6 +254,7 @@ ERST
         .help       = "save screen from head 'head' of display device 'device' "
                       "into PPM image 'filename'",
         .cmd        = hmp_screendump,
+        .coroutine  = true,
     },
 
 SRST
diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
index 56e9bad..a6a6684 100644
--- a/monitor/hmp-cmds.c
+++ b/monitor/hmp-cmds.c
@@ -1762,7 +1762,8 @@ err_out:
     goto out;
 }
 
-void hmp_screendump(Monitor *mon, const QDict *qdict)
+void coroutine_fn
+hmp_screendump(Monitor *mon, const QDict *qdict)
 {
     const char *filename = qdict_get_str(qdict, "filename");
     const char *id = qdict_get_try_str(qdict, "device");
diff --git a/qapi/ui.json b/qapi/ui.json
index 9d67210..6c7b33c 100644
--- a/qapi/ui.json
+++ b/qapi/ui.json
@@ -98,7 +98,8 @@
 #
 ##
 { 'command': 'screendump',
-  'data': {'filename': 'str', '*device': 'str', '*head': 'int'} }
+  'data': {'filename': 'str', '*device': 'str', '*head': 'int'},
+  'coroutine': true }
 
 ##
 # == Spice
diff --git a/ui/console.c b/ui/console.c
index 820e408..e8e5970 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -168,6 +168,7 @@ struct QemuConsole {
     QEMUFIFO out_fifo;
     uint8_t out_fifo_buf[16];
     QEMUTimer *kbd_timer;
+    CoQueue dump_queue;
 
     QTAILQ_ENTRY(QemuConsole) next;
 };
@@ -195,7 +196,6 @@ static void dpy_refresh(DisplayState *s);
 static DisplayState *get_alloc_displaystate(void);
 static void text_console_update_cursor_timer(void);
 static void text_console_update_cursor(void *opaque);
-static bool ppm_save(int fd, DisplaySurface *ds, Error **errp);
 
 static void gui_update(void *opaque)
 {
@@ -264,6 +264,7 @@ static void gui_setup_refresh(DisplayState *ds)
 
 void graphic_hw_update_done(QemuConsole *con)
 {
+    qemu_co_queue_restart_all(&con->dump_queue);
 }
 
 void graphic_hw_update(QemuConsole *con)
@@ -311,16 +312,16 @@ void graphic_hw_invalidate(QemuConsole *con)
     }
 }
 
-static bool ppm_save(int fd, DisplaySurface *ds, Error **errp)
+static bool ppm_save(int fd, pixman_image_t *image, Error **errp)
 {
-    int width = pixman_image_get_width(ds->image);
-    int height = pixman_image_get_height(ds->image);
+    int width = pixman_image_get_width(image);
+    int height = pixman_image_get_height(image);
     g_autoptr(Object) ioc = OBJECT(qio_channel_file_new_fd(fd));
     g_autofree char *header = NULL;
     g_autoptr(pixman_image_t) linebuf = NULL;
     int y;
 
-    trace_ppm_save(fd, ds);
+    trace_ppm_save(fd, image);
 
     header = g_strdup_printf("P6\n%d %d\n%d\n", width, height, 255);
     if (qio_channel_write_all(QIO_CHANNEL(ioc),
@@ -330,7 +331,7 @@ static bool ppm_save(int fd, DisplaySurface *ds, Error **errp)
 
     linebuf = qemu_pixman_linebuf_create(PIXMAN_BE_r8g8b8, width);
     for (y = 0; y < height; y++) {
-        qemu_pixman_linebuf_fill(linebuf, ds->image, width, 0, y);
+        qemu_pixman_linebuf_fill(linebuf, image, width, 0, y);
         if (qio_channel_write_all(QIO_CHANNEL(ioc),
                                   (char *)pixman_image_get_data(linebuf),
                                   pixman_image_get_stride(linebuf), errp) < 0) {
@@ -341,9 +342,17 @@ static bool ppm_save(int fd, DisplaySurface *ds, Error **errp)
     return true;
 }
 
-void qmp_screendump(const char *filename, bool has_device, const char *device,
-                    bool has_head, int64_t head, Error **errp)
+static void graphic_hw_update_bh(void *con)
 {
+    graphic_hw_update(con);
+}
+
+/* Safety: coroutine-only, concurrent-coroutine safe, main thread only */
+void coroutine_fn
+qmp_screendump(const char *filename, bool has_device, const char *device,
+               bool has_head, int64_t head, Error **errp)
+{
+    g_autoptr(pixman_image_t) image = NULL;
     QemuConsole *con;
     DisplaySurface *surface;
     int fd;
@@ -366,12 +375,24 @@ void qmp_screendump(const char *filename, bool has_device, const char *device,
         }
     }
 
-    graphic_hw_update(con);
+    if (qemu_co_queue_empty(&con->dump_queue)) {
+        /* Defer the update, it will restart the pending coroutines */
+        aio_bh_schedule_oneshot(qemu_get_aio_context(),
+                                graphic_hw_update_bh, con);
+    }
+    qemu_co_queue_wait(&con->dump_queue, NULL);
+
+    /*
+     * All pending coroutines are woken up, while the BQL is held.  No
+     * further graphic update are possible until it is released.  Take
+     * an image ref before that.
+     */
     surface = qemu_console_surface(con);
     if (!surface) {
         error_setg(errp, "no surface");
         return;
     }
+    image = pixman_image_ref(surface->image);
 
     fd = qemu_open_old(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, 0666);
     if (fd == -1) {
@@ -380,7 +401,12 @@ void qmp_screendump(const char *filename, bool has_device, const char *device,
         return;
     }
 
-    if (!ppm_save(fd, surface, errp)) {
+    /*
+     * The image content could potentially be updated as the coroutine
+     * yields and releases the BQL. It could produce corrupted dump, but
+     * it should be otherwise safe.
+     */
+    if (!ppm_save(fd, image, errp)) {
         qemu_unlink(filename);
     }
 }
@@ -1296,6 +1322,7 @@ static QemuConsole *new_console(DisplayState *ds, console_type_t console_type,
 
     obj = object_new(TYPE_QEMU_CONSOLE);
     s = QEMU_CONSOLE(obj);
+    qemu_co_queue_init(&s->dump_queue);
     s->head = head;
     object_property_add_link(obj, "device", TYPE_DEVICE,
                              (Object **)&s->device,
diff --git a/ui/trace-events b/ui/trace-events
index b7d7270..0ffcdb4 100644
--- a/ui/trace-events
+++ b/ui/trace-events
@@ -15,7 +15,7 @@ displaysurface_create_pixman(void *display_surface) "surface=%p"
 displaysurface_free(void *display_surface) "surface=%p"
 displaychangelistener_register(void *dcl, const char *name) "%p [ %s ]"
 displaychangelistener_unregister(void *dcl, const char *name) "%p [ %s ]"
-ppm_save(int fd, void *display_surface) "fd=%d surface=%p"
+ppm_save(int fd, void *image) "fd=%d image=%p"
 
 # gtk-egl.c
 # gtk-gl-area.c
diff --git a/util/qemu-coroutine-lock.c b/util/qemu-coroutine-lock.c
index 36927b5..5816bf8 100644
--- a/util/qemu-coroutine-lock.c
+++ b/util/qemu-coroutine-lock.c
@@ -85,15 +85,13 @@ static bool qemu_co_queue_do_restart(CoQueue *queue, bool single)
     return true;
 }
 
-bool coroutine_fn qemu_co_queue_next(CoQueue *queue)
+bool qemu_co_queue_next(CoQueue *queue)
 {
-    assert(qemu_in_coroutine());
     return qemu_co_queue_do_restart(queue, true);
 }
 
-void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue)
+void qemu_co_queue_restart_all(CoQueue *queue)
 {
-    assert(qemu_in_coroutine());
     qemu_co_queue_do_restart(queue, false);
 }