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gl/dispmanx: fix deadlock triggered by set_render_rectangle
When the gstglimagesink is started with the option `glimagesink
render-rectangle="<0,0,1920,1080>"`, the pipeline reaches a deadlock.
The reason the deadlock occurs is that the
`gst_gl_window_set_render_rectangle` takes locks on the window, in
addition it calls `window_class->set_render_rectangle(...)` which
executes the `_on_resize` function. Since the `_on_resize` function also
takes locks on the window the deadlock is achieved.

By scheduling the adjustment of the render rectangle through an async
message for `gst_gl_window_dispmanx_set_render_rectangle`, the actual
resize happens in another context and therefore doesn't suffers from the
lock taken in `gst_gl_window_set_render_rectangle`.

This solution follows the same approach as gl/wayland. The problem was
introduced by b887db1. For the full discussion check #849.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/merge_requests/1030>
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Alexander Vandenbulcke committed Feb 10, 2021
1 parent 278b10d commit 57029ba
Showing 1 changed file with 41 additions and 6 deletions.
47 changes: 41 additions & 6 deletions gst-libs/gst/gl/dispmanx/gstglwindow_dispmanx_egl.c
Expand Up @@ -286,18 +286,53 @@ window_resize (GstGLWindowDispmanxEGL * window_egl, guint width, guint height,
window_egl->native.height = height;
}

struct SetRenderRectangle
{
GstGLWindowDispmanxEGL *window_egl;
GstVideoRectangle rect;
};

static void
_free_set_render_rectangle (struct SetRenderRectangle *render)
{
if (render) {
if (render->window_egl)
gst_object_unref (render->window_egl);
g_free (render);
}
}

static void
_set_render_rectangle (gpointer data)
{
struct SetRenderRectangle *render = data;

GST_LOG_OBJECT (render->window_egl, "setting render rectangle %i,%i+%ix%i",
render->rect.x, render->rect.y, render->rect.w, render->rect.h);

window_resize (render->window_egl, render->rect.w, render->rect.h, TRUE);

render->window_egl->render_rect = render->rect;
}

static gboolean
gst_gl_window_dispmanx_egl_set_render_rectangle (GstGLWindow * window,
gint x, gint y, gint width, gint height)
{
GstGLWindowDispmanxEGL *window_egl = GST_GL_WINDOW_DISPMANX_EGL (window);
window_egl->render_rect.x = x;
window_egl->render_rect.y = y;
window_egl->render_rect.w = width;
window_egl->render_rect.h = height;
struct SetRenderRectangle *render;

render = g_new0 (struct SetRenderRectangle, 1);
render->window_egl = gst_object_ref (window_egl);
render->rect.x = x;
render->rect.y = y;
render->rect.w = width;
render->rect.h = height;

gst_gl_window_send_message_async (window,
(GstGLWindowCB) _set_render_rectangle, render,
(GDestroyNotify) _free_set_render_rectangle);

window_resize (window_egl, window_egl->render_rect.w,
window_egl->render_rect.h, TRUE);
return TRUE;
}

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