glcontext: track sharedness with a cookie

The previous approach of traversing the other_context weak ref tree was
1. Less performant
2. Incorrect for context destruction removing a link in the tree

Example of 2:
c1 = context_create (NULL)
c2 = context_create (c1)
c3 = context_create (c2)
context_can_share (c1, c3) == TRUE
context_destroy (c2)
unref (c2)
context_can_share (c1, c3) returns FALSE when it should be TRUE!

This does not remove the restriction that context sharedness can only
be tracked between GstGLContext's.
This commit is contained in:
Matthew Waters 2015-07-16 00:37:58 +10:00
parent b679cc2238
commit be9ad5eeb2
2 changed files with 80 additions and 48 deletions

View file

@ -133,6 +133,35 @@ load_self_module (gpointer user_data)
#error "Add module loading support for GLES3"
#endif
/* Context sharedness es tracked by a unique id stored in each context object
* in order track complex creation/deletion scenarios. As a result, sharedness
* can only be successfully validated between two GstGLContext's where one is
* not a wrapped context.
*
* As there is no API at the winsys level to tell whether two OpenGL contexts
* can share GL resources, this is the next best thing.
*/
static volatile guint sharegroup_idx;
static guint
_new_sharegroup_id (void)
{
guint current, ret;
do {
current = g_atomic_int_get (&sharegroup_idx);
ret = current + 1;
/* 0 is special */
if (ret == 0)
ret++;
} while (!g_atomic_int_compare_and_exchange (&sharegroup_idx, current, ret));
GST_TRACE ("generated new share group id %u", ret);
return ret;
}
#define GST_CAT_DEFAULT gst_gl_context_debug
GST_DEBUG_CATEGORY (GST_CAT_DEFAULT);
@ -163,6 +192,7 @@ struct _GstGLContextPrivate
gboolean alive;
GWeakRef other_context_ref;
guint sharegroup_id;
GError **error;
gint gl_major;
@ -359,6 +389,7 @@ gst_gl_context_new_wrapped (GstGLDisplay * display, guintptr handle,
context = (GstGLContext *) context_wrap;
context->display = gst_object_ref (display);
context->priv->sharegroup_id = _new_sharegroup_id ();
context_wrap->handle = handle;
context_wrap->platform = context_type;
context_wrap->available_apis = available_apis;
@ -822,53 +853,13 @@ gst_gl_context_get_window (GstGLContext * context)
return gst_object_ref (context->window);
}
static gboolean
_share_group_descendant (GstGLContext * context, GstGLContext * other_context,
GstGLContext ** root)
{
GstGLContext *next = gst_object_ref (context);
GstGLContext *prev = NULL;
/* given a context tree where --> means "has other gl context":
*
* a-->b-->c-->d
* / /
* e /
* /
* f-->g
*
* return TRUE if @other_context is a descendant of @context
*
* e.g. [a, b], [f, d], [e, c] are all descendants
* but [b, a], [d, f], [e, f] are not descendants. Provide the root node (d)
* so that we can check if two chains end up at the end with the same
* GstGLContext
*/
while (next != NULL) {
if (next == other_context) {
gst_object_unref (next);
if (root)
*root = NULL;
return TRUE;
}
prev = next;
next = g_weak_ref_get (&next->priv->other_context_ref);
gst_object_unref (prev);
}
if (root != NULL)
*root = prev;
return FALSE;
}
/**
* gst_gl_context_can_share:
* @context: a #GstGLContext
* @other_context: another #GstGLContext
*
* Note: This will always fail for two wrapped #GstGLContext's
*
* Returns: whether @context and @other_context are able to share OpenGL
* resources.
*
@ -877,16 +868,12 @@ _share_group_descendant (GstGLContext * context, GstGLContext * other_context,
gboolean
gst_gl_context_can_share (GstGLContext * context, GstGLContext * other_context)
{
GstGLContext *root1, *root2;
g_return_val_if_fail (GST_GL_IS_CONTEXT (context), FALSE);
g_return_val_if_fail (GST_GL_IS_CONTEXT (other_context), FALSE);
/* check if the contexts are descendants or the root nodes are the same */
return context == other_context
|| _share_group_descendant (context, other_context, &root1)
|| _share_group_descendant (other_context, context, &root2)
|| ((root1 != NULL || root2 != NULL) && root1 == root2);
return context->priv->sharegroup_id != 0
&& context->priv->sharegroup_id == other_context->priv->sharegroup_id;
}
/**
@ -926,6 +913,10 @@ gst_gl_context_create (GstGLContext * context,
if (!context->priv->created) {
g_weak_ref_set (&context->priv->other_context_ref, other_context);
context->priv->error = error;
if (other_context == NULL)
context->priv->sharegroup_id = _new_sharegroup_id ();
else
context->priv->sharegroup_id = other_context->priv->sharegroup_id;
context->priv->gl_thread = g_thread_new ("gstglcontext",
(GThreadFunc) gst_gl_context_create_thread, context);

View file

@ -442,6 +442,46 @@ GST_START_TEST (test_current_context)
GST_END_TEST;
GST_START_TEST (test_context_can_share)
{
GstGLContext *c1, *c2, *c3;
GError *error = NULL;
c1 = gst_gl_context_new (display);
gst_gl_context_create (c1, NULL, &error);
fail_if (error != NULL, "Error creating context %s\n",
error ? error->message : "Unknown Error");
c2 = gst_gl_context_new (display);
gst_gl_context_create (c2, c1, &error);
fail_if (error != NULL, "Error creating context %s\n",
error ? error->message : "Unknown Error");
fail_unless (gst_gl_context_can_share (c1, c2));
fail_unless (gst_gl_context_can_share (c2, c1));
c3 = gst_gl_context_new (display);
gst_gl_context_create (c3, c2, &error);
fail_if (error != NULL, "Error creating context %s\n",
error ? error->message : "Unknown Error");
fail_unless (gst_gl_context_can_share (c1, c3));
fail_unless (gst_gl_context_can_share (c3, c1));
fail_unless (gst_gl_context_can_share (c2, c3));
fail_unless (gst_gl_context_can_share (c3, c2));
/* destroy the middle context */
gst_object_unref (c2);
c2 = NULL;
fail_unless (gst_gl_context_can_share (c1, c3));
fail_unless (gst_gl_context_can_share (c3, c1));
gst_object_unref (c1);
gst_object_unref (c3);
}
GST_END_TEST;
static Suite *
gst_gl_context_suite (void)
@ -454,6 +494,7 @@ gst_gl_context_suite (void)
tcase_add_test (tc_chain, test_share);
tcase_add_test (tc_chain, test_wrapped_context);
tcase_add_test (tc_chain, test_current_context);
tcase_add_test (tc_chain, test_context_can_share);
return s;
}