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gstelement: protect async state changes against spurious wake ups

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When a pipeline is pre-rolling, it waits for all sink elements to report
they have received a buffer before completing the transition to paused.
This async wait is done using a state condition variable. The way this
waits are currently implemented do not protect against spurious conditional
wake ups, which may happen due to external factors in the kernel.

This change implements the wait within a loop that iterates over the protected
variable to reinitiates the wait if the wakeup was spurious. More details in
the [GCond docs](https://docs.gtk.org/glib/struct.Cond.html).

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4086>
This commit is contained in:
Michael Gruner 2023-02-28 11:48:27 -06:00 committed by GStreamer Marge Bot
parent 6ce4a12f0b
commit 53c145a158
1 changed files with 57 additions and 49 deletions
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106
subprojects/gstreamer/gst/gstelement.c
View file

@ -2500,72 +2500,80 @@ gst_element_get_state_func (GstElement * element,
{
GstStateChangeReturn ret = GST_STATE_CHANGE_FAILURE;
GstState old_pending;
gint64 end_time;
GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "getting state, timeout %"
GST_TIME_FORMAT, GST_TIME_ARGS (timeout));
GST_OBJECT_LOCK (element);
ret = GST_STATE_RETURN (element);
GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "RETURN is %s",
gst_element_state_change_return_get_name (ret));
/* we got an error, report immediately */
if (ret == GST_STATE_CHANGE_FAILURE)
goto done;
if (timeout != GST_CLOCK_TIME_NONE) {
/* make timeout absolute */
end_time = g_get_monotonic_time () + (timeout / 1000);
}
/* we got no_preroll, report immediately */
if (ret == GST_STATE_CHANGE_NO_PREROLL)
goto done;
do {
ret = GST_STATE_RETURN (element);
GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "RETURN is %s",
gst_element_state_change_return_get_name (ret));
/* no need to wait async if we are not async */
if (ret != GST_STATE_CHANGE_ASYNC)
goto done;
/* we got an error, report immediately */
if (ret == GST_STATE_CHANGE_FAILURE)
goto done;
old_pending = GST_STATE_PENDING (element);
if (old_pending != GST_STATE_VOID_PENDING) {
gboolean signaled;
guint32 cookie;
/* we got no_preroll, report immediately */
if (ret == GST_STATE_CHANGE_NO_PREROLL)
goto done;
/* get cookie to detect state changes during waiting */
cookie = element->state_cookie;
/* no need to wait async if we are not async */
if (ret != GST_STATE_CHANGE_ASYNC)
goto done;
GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
"waiting for element to commit state");
old_pending = GST_STATE_PENDING (element);
if (old_pending != GST_STATE_VOID_PENDING) {
gboolean signaled = TRUE;
guint32 cookie;
/* we have a pending state change, wait for it to complete */
if (timeout != GST_CLOCK_TIME_NONE) {
gint64 end_time;
/* make timeout absolute */
end_time = g_get_monotonic_time () + (timeout / 1000);
signaled = GST_STATE_WAIT_UNTIL (element, end_time);
} else {
GST_STATE_WAIT (element);
signaled = TRUE;
}
/* get cookie to detect state changes during waiting */
cookie = element->state_cookie;
if (!signaled) {
GST_CAT_INFO_OBJECT (GST_CAT_STATES, element, "timed out");
/* timeout triggered */
ret = GST_STATE_CHANGE_ASYNC;
} else {
if (cookie != element->state_cookie)
goto interrupted;
GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
"waiting for element to commit state");
/* could be success or failure */
if (old_pending == GST_STATE (element)) {
GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "got success");
ret = GST_STATE_CHANGE_SUCCESS;
/* we have a pending state change, wait for it to complete or for
an interruption */
if (timeout != GST_CLOCK_TIME_NONE) {
signaled = GST_STATE_WAIT_UNTIL (element, end_time);
} else {
GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "got failure");
ret = GST_STATE_CHANGE_FAILURE;
GST_STATE_WAIT (element);
signaled = TRUE;
}
if (!signaled) {
GST_CAT_INFO_OBJECT (GST_CAT_STATES, element, "timed out");
/* timeout triggered */
ret = GST_STATE_CHANGE_ASYNC;
goto done;
} else {
if (cookie != element->state_cookie)
goto interrupted;
/* could be success or failure */
if (old_pending == GST_STATE (element)) {
GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "got success");
ret = GST_STATE_CHANGE_SUCCESS;
} else {
GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "got failure");
ret = GST_STATE_CHANGE_FAILURE;
}
}
/* if nothing is pending anymore we can return SUCCESS */
if (GST_STATE_PENDING (element) == GST_STATE_VOID_PENDING) {
GST_CAT_LOG_OBJECT (GST_CAT_STATES, element, "nothing pending");
ret = GST_STATE_CHANGE_SUCCESS;
}
}
/* if nothing is pending anymore we can return SUCCESS */
if (GST_STATE_PENDING (element) == GST_STATE_VOID_PENDING) {
GST_CAT_LOG_OBJECT (GST_CAT_STATES, element, "nothing pending");
ret = GST_STATE_CHANGE_SUCCESS;
}
}
} while (old_pending != GST_STATE (element));
done:
if (state)