[Qemu-devel] [PATCH v2 23/25] console: make screendump async

[Marc-André Lureau]

Make screendump async to provide correct screendumps.

HMP doesn't have async support, so it has to remain sync to avoid
potential races.

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

Signed-off-by: Marc-André Lureau <address@hidden>
---
 qapi-schema.json     |  5 +++-
 include/ui/console.h |  1 +
 hmp.c                |  2 +-
 ui/console.c         | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 4 files changed, 73 insertions(+), 3 deletions(-)

diff --git a/qapi-schema.json b/qapi-schema.json
index 2e7c96c122..2af8661357 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -4686,6 +4686,9 @@
 #
 # Returns: Nothing on success
 #
+# Note: the operation can be cancelled and the file not written if the
+# client disconnects before completion.
+#
 # Since: 0.14.0
 #
 # Example:
@@ -4695,7 +4698,7 @@
 # <- { "return": {} }
 #
 ##
-{ 'command': 'screendump', 'data': {'filename': 'str'} }
+{ 'command': 'screendump', 'data': {'filename': 'str'}, 'async': true }
 
 
 ##
diff --git a/include/ui/console.h b/include/ui/console.h
index e2d4f0df0d..4199e7008a 100644
--- a/include/ui/console.h
+++ b/include/ui/console.h
@@ -75,6 +75,7 @@ struct MouseTransformInfo {
 };
 
 void hmp_mouse_set(Monitor *mon, const QDict *qdict);
+void hmp_screendump_sync(const char *filename, Error **errp);
 
 /* keysym is a unicode code except for special keys (see QEMU_KEY_xxx
    constants) */
diff --git a/hmp.c b/hmp.c
index 8522efea26..6586247a31 100644
--- a/hmp.c
+++ b/hmp.c
@@ -1917,7 +1917,7 @@ void hmp_screendump(Monitor *mon, const QDict *qdict)
     const char *filename = qdict_get_str(qdict, "filename");
     Error *err = NULL;
 
-    qmp_screendump(filename, &err);
+    hmp_screendump_sync(filename, &err);
     hmp_handle_error(mon, &err);
 }
 
diff --git a/ui/console.c b/ui/console.c
index 46ad6abd94..199296525c 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -114,6 +114,12 @@ typedef enum {
     TEXT_CONSOLE_FIXED_SIZE
 } console_type_t;
 
+struct qmp_screendump {
+    gchar *filename;
+    QmpReturn *ret;
+    QLIST_ENTRY(qmp_screendump) link;
+};
+
 struct QemuConsole {
     Object parent;
 
@@ -163,6 +169,8 @@ struct QemuConsole {
     QEMUFIFO out_fifo;
     uint8_t out_fifo_buf[16];
     QEMUTimer *kbd_timer;
+
+    QLIST_HEAD(, qmp_screendump) qmp_screendumps;
 };
 
 struct DisplayState {
@@ -188,6 +196,8 @@ 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 void ppm_save(const char *filename, DisplaySurface *ds,
+                     Error **errp);
 
 static void gui_update(void *opaque)
 {
@@ -254,8 +264,39 @@ static void gui_setup_refresh(DisplayState *ds)
     ds->have_text = have_text;
 }
 
+static void qmp_screendump_finish(QemuConsole *con, const char *filename,
+                                  QmpReturn *ret)
+{
+    Error *err = NULL;
+    DisplaySurface *surface;
+
+    if (qmp_return_is_cancelled(ret)) {
+        return;
+    }
+
+    surface = qemu_console_surface(con);
+
+    /* FIXME: async save with coroutine? it would have to copy or lock
+     * the surface. */
+    ppm_save(filename, surface, &err);
+
+    if (err) {
+        qmp_return_error(ret, err);
+    } else {
+        qmp_screendump_return(ret);
+    }
+}
+
 void graphic_hw_update_done(QemuConsole *con)
 {
+    struct qmp_screendump *dump, *next;
+
+    QLIST_FOREACH_SAFE(dump, &con->qmp_screendumps, link, next) {
+        qmp_screendump_finish(con, dump->filename, dump->ret);
+        g_free(dump->filename);
+        QLIST_REMOVE(dump, link);
+        g_free(dump);
+    }
 }
 
 bool graphic_hw_update(QemuConsole *con)
@@ -356,7 +397,8 @@ write_err:
     goto out;
 }
 
-void qmp_screendump(const char *filename, Error **errp)
+/* this sync screendump may produce outdated dumps: use qmp instead */
+void hmp_screendump_sync(const char *filename, Error **errp)
 {
     QemuConsole *con = qemu_console_lookup_by_index(0);
     DisplaySurface *surface;
@@ -371,6 +413,29 @@ void qmp_screendump(const char *filename, Error **errp)
     ppm_save(filename, surface, errp);
 }
 
+void qmp_screendump(const char *filename, QmpReturn *qret)
+{
+    QemuConsole *con = qemu_console_lookup_by_index(0);
+    bool async;
+    Error *err = NULL;
+
+    if (con == NULL) {
+        error_setg(&err, "There is no QemuConsole I can screendump from.");
+        qmp_return_error(qret, err);
+        return;
+    }
+
+    async = graphic_hw_update(con);
+    if (async) {
+        struct qmp_screendump *dump = g_new(struct qmp_screendump, 1);
+        dump->filename = g_strdup(filename);
+        dump->ret = qret;
+        QLIST_INSERT_HEAD(&con->qmp_screendumps, dump, link);
+    } else {
+        qmp_screendump_finish(con, filename, qret);
+    }
+}
+
 void graphic_hw_text_update(QemuConsole *con, console_ch_t *chardata)
 {
     if (!con) {
@@ -1248,6 +1313,7 @@ static QemuConsole *new_console(DisplayState *ds, 
console_type_t console_type,
     obj = object_new(TYPE_QEMU_CONSOLE);
     s = QEMU_CONSOLE(obj);
     s->head = head;
+    QLIST_INIT(&s->qmp_screendumps);
     object_property_add_link(obj, "device", TYPE_DEVICE,
                              (Object **)&s->device,
                              object_property_allow_set_link,
-- 
2.11.0.295.gd7dffce1c