[Qemu-devel] [PATCH] sdl: Avoid unnecessary resizing of the display surface

[Stefan Weil]

If neither width nor height changes, nothing has to be done.

Cc: Anthony Liguori <address@hidden>
Signed-off-by: Stefan Weil <address@hidden>
---

This patch improves SDL for any host (for example with remote X displays),
but the main reason why I wrote it was another problem:

On w32 / w64 hosts, qemu-system-arm has a deadlock when it calls
sdl_resize_displaysurface during Linux boot. One thread waits for
a critical region, another thread waits inside SDL_SetVideoMode.

The patch avoids this problem. Paolo, maybe you have an idea what
could cause the deadlock. Debugging on wxx is terrible - up to now,
I did not succeed in analysing the lock situation with gdb.

Regards,
Stefan W.

 ui/sdl.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/ui/sdl.c b/ui/sdl.c
index 8700b7a..8c1c71c 100644
--- a/ui/sdl.c
+++ b/ui/sdl.c
@@ -224,8 +224,11 @@ static void sdl_free_displaysurface(DisplaySurface 
*surface)
 
 static DisplaySurface* sdl_resize_displaysurface(DisplaySurface *surface, int 
width, int height)
 {
-    sdl_free_displaysurface(surface);
-    return sdl_create_displaysurface(width, height);
+    if (surface->width != width || surface->height != height) {
+        sdl_free_displaysurface(surface);
+        surface = sdl_create_displaysurface(width, height);
+    }
+    return surface;
 }
 
 /* generic keyboard conversion */
-- 
1.7.9