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pad: gst_pad_activate_mode() always succeed if same mode

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Checking that the pad is in the correct mode before the parent is
checked makes the call always succeed if the mode is ok.

This fixes a race with ghostpad where gst_pad_activate_mode() could
trigger a g_critical() if the ghostpad is unparented while the
proxypad is deactivating, for instance if the ghostpad is released.
More specifically, gst_ghost_pad_internal_activate_push_default()'s
call to gst_pad_activate_mode() would fail if ghostpad doesn't have a
parent. With this patch it will return true of mode is already
correct.
This commit is contained in:
Stian Selnes 2017-08-18 14:30:32 +02:00 committed by Tim-Philipp Müller
parent df27ec3e67
commit 512cec3dea
2 changed files with 49 additions and 0 deletions
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15
gst/gstpad.c
View file

@ -1303,11 +1303,19 @@ gst_pad_activate_mode (GstPad * pad, GstPadMode mode, gboolean active)
{
GstObject *parent;
gboolean res;
GstPadMode old, new;
g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
GST_OBJECT_LOCK (pad);
old = GST_PAD_MODE (pad);
new = active ? mode : GST_PAD_MODE_NONE;
if (old == new)
goto was_ok;
ACQUIRE_PARENT (pad, parent, no_parent);
GST_OBJECT_UNLOCK (pad);
res = activate_mode_internal (pad, parent, mode, active);
@ -1316,6 +1324,13 @@ gst_pad_activate_mode (GstPad * pad, GstPadMode mode, gboolean active)
return res;
was_ok:
{
GST_OBJECT_UNLOCK (pad);
GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "already %s in %s mode",
active ? "activated" : "deactivated", gst_pad_mode_get_name (mode));
return TRUE;
}
no_parent:
{
GST_WARNING_OBJECT (pad, "no parent");

34
tests/check/gst/gstghostpad.c
View file

@ -1322,6 +1322,7 @@ GST_START_TEST (test_activate_sink_switch_mode)
GST_END_TEST;
static gboolean thread_running;
static gpointer
send_query_to_pad_func (GstPad * pad)
{
@ -1366,6 +1367,38 @@ GST_START_TEST (test_stress_upstream_queries_while_tearing_down)
GST_END_TEST;
GST_START_TEST (test_deactivate_already_deactive_with_no_parent)
{
/* This simulates the behavior where a ghostpad is released while
* deactivating (for instance because of a state change).
* gst_pad_activate_mode() may be be called from
* gst_ghost_pad_internal_activate_push_default() on a pad that is already
* deactivate and unparented. The call chain is really like somethink like
* this:
* gst_pad_activate_mode(ghostpad)
* -> ...
* -> gst_pad_activate_mode(proxypad)
* -> ...
* -> gst_pad_activate_mode(ghostpad)
*/
GstElement *bin = gst_bin_new ("testbin");
GstPad *pad = gst_ghost_pad_new_no_target ("src", GST_PAD_SRC);
gst_object_ref (pad);
/* We need to add/remove pad because that will update the pad's flags */
fail_unless (gst_element_add_pad (bin, pad));
fail_unless (gst_element_remove_pad (bin, pad));
/* Setting a pad that's already deactive to deactive should not fail. */
fail_if (gst_pad_is_active (pad));
fail_unless (gst_pad_activate_mode (pad, GST_PAD_MODE_PUSH, FALSE));
gst_object_unref (bin);
gst_object_unref (pad);
}
GST_END_TEST;
static Suite *
gst_ghost_pad_suite (void)
{
@ -1396,6 +1429,7 @@ gst_ghost_pad_suite (void)
tcase_add_test (tc_chain, test_activate_sink_and_src);
tcase_add_test (tc_chain, test_activate_src_pull_mode);
tcase_add_test (tc_chain, test_activate_sink_switch_mode);
tcase_add_test (tc_chain, test_deactivate_already_deactive_with_no_parent);
tcase_add_test (tc_chain, test_stress_upstream_queries_while_tearing_down);
return s;