[PATCH] console: make QMP screendump use coroutine

[Marc-André Lureau]

Thanks to the QMP coroutine support, the screendump handler can
trigger a graphic_hw_update(), yield and let the main loop run until
update is done. Then the handler is resumed, and the ppm_save() will
write the screen image to disk in the coroutine context (thus
non-blocking).

For now, HMP doesn't have coroutine support, so it remains potentially
outdated or glitched.

Fixes:
https://bugzilla.redhat.com/show_bug.cgi?id=1230527

Based-on: <address@hidden>

Cc: Kevin Wolf <address@hidden>
Signed-off-by: Marc-André Lureau <address@hidden>
---
 qapi/ui.json    |  3 ++-
 ui/console.c    | 35 +++++++++++++++++++++++++++--------
 ui/trace-events |  2 +-
 3 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/qapi/ui.json b/qapi/ui.json
index e04525d8b4..d941202f34 100644
--- a/qapi/ui.json
+++ b/qapi/ui.json
@@ -96,7 +96,8 @@
 #
 ##
 { '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 ac79d679f5..db184b473f 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -167,6 +167,7 @@ struct QemuConsole {
     QEMUFIFO out_fifo;
     uint8_t out_fifo_buf[16];
     QEMUTimer *kbd_timer;
+    Coroutine *screendump_co;
 
     QTAILQ_ENTRY(QemuConsole) next;
 };
@@ -194,7 +195,6 @@ 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)
 {
@@ -263,6 +263,9 @@ static void gui_setup_refresh(DisplayState *ds)
 
 void graphic_hw_update_done(QemuConsole *con)
 {
+    if (con && con->screendump_co) {
+        aio_co_wake(con->screendump_co);
+    }
 }
 
 void graphic_hw_update(QemuConsole *con)
@@ -310,16 +313,16 @@ 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),
@@ -329,7 +332,7 @@ 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) 
{
@@ -340,11 +343,18 @@ static bool ppm_save(int fd, DisplaySurface *ds, Error 
**errp)
     return true;
 }
 
+static void graphic_hw_update_bh(void *con)
+{
+    graphic_hw_update(con);
+}
+
+/* may be called in coroutine context or not */
 void qmp_screendump(const char *filename, bool has_device, const char *device,
                     bool has_head, int64_t head, Error **errp)
 {
     QemuConsole *con;
     DisplaySurface *surface;
+    g_autoptr(pixman_image_t) image = NULL;
     int fd;
 
     if (has_device) {
@@ -365,7 +375,15 @@ void qmp_screendump(const char *filename, bool has_device, 
const char *device,
         }
     }
 
-    graphic_hw_update(con);
+    if (qemu_in_coroutine()) {
+        assert(!con->screendump_co);
+        con->screendump_co = qemu_coroutine_self();
+        aio_bh_schedule_oneshot(qemu_get_aio_context(),
+                                graphic_hw_update_bh, con);
+        qemu_coroutine_yield();
+        con->screendump_co = NULL;
+    }
+
     surface = qemu_console_surface(con);
     if (!surface) {
         error_setg(errp, "no surface");
@@ -379,7 +397,8 @@ void qmp_screendump(const char *filename, bool has_device, 
const char *device,
         return;
     }
 
-    if (!ppm_save(fd, surface, errp)) {
+    image = pixman_image_ref(surface->image);
+    if (!ppm_save(fd, image, errp)) {
         qemu_unlink(filename);
     }
 }
diff --git a/ui/trace-events b/ui/trace-events
index 0dcda393c1..e8726fc969 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.c
 # gtk-gl-area.c
-- 
2.25.0.rc2.1.g09a9a1a997