FaSTTUBe/GST-Tensordecoder-ov_ep
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tracers: Fix deadlock in latency tracer

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Fixes https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/4317

This patch fixes a regression in
a35bf1e3847351703542869755b6b9e536b9d2fd.

The new calls to tracers in the affected change were being done while
holding the pad object lock, which wasn't the case in the old ones,
leading to the latency tracer deadlocking in gst_object_get_parent().

The dependency on the pad lock for those calls was accidental. This
patch removes it by temporarily unlocking during the affected calls,
not unlike how it's done when calling a probe callback or the
send_event() function of the downstream element.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8925>
This commit is contained in:
Alicia Boya García 2025-05-02 10:23:18 +02:00 committed by GStreamer Marge Bot
parent ddd6a708cb
commit 371100c743
2 changed files with 44 additions and 8 deletions
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4
girs/Gst-1.0.gir
View File

@ -32820,11 +32820,11 @@ MT safe.</doc>
</return-value>
<parameters>
<instance-parameter name="pad" transfer-ownership="none">
<doc xml:space="preserve" filename="../subprojects/gstreamer/gst/gstpad.c">a #GstPad to push the event to.</doc>
<doc xml:space="preserve" filename="../subprojects/gstreamer/gst/gstpad.c">the #GstPad that will push the event.</doc>
<type name="Pad" c:type="GstPad*"/>
</instance-parameter>
<parameter name="event" transfer-ownership="full">
<doc xml:space="preserve" filename="../subprojects/gstreamer/gst/gstpad.c">the #GstEvent to send to the pad.</doc>
<doc xml:space="preserve" filename="../subprojects/gstreamer/gst/gstpad.c">the #GstEvent to push out of the pad.</doc>
<type name="Event" c:type="GstEvent*"/>
</parameter>
</parameters>

48
subprojects/gstreamer/gst/gstpad.c
View File

@ -4075,7 +4075,14 @@ typedef struct
GstEvent *event;
} PushStickyData;
/* should be called with pad LOCK */
/* Push the sticky event in the #PadEvent pointed by @ev.
*
* Must be called with pad LOCK.
*
* This function will temporarily unlock the pad during the event push, so care
* must be taken that all the arguments remain valid during the entire duration
* of the call. Note that events_foreach() already guarantees this by making a
* stack copy of PadEvent and increasing the reference count of the event. */
static gboolean
push_sticky (GstPad * pad, PadEvent * ev, gpointer user_data)
{
@ -4101,10 +4108,25 @@ push_sticky (GstPad * pad, PadEvent * ev, gpointer user_data)
data_sticky_order < ev->sticky_order) {
data->ret = GST_FLOW_CUSTOM_SUCCESS_1;
} else {
GST_OBJECT_UNLOCK (pad);
/* The event argument remains valid during the unlock as the caller must
* hold a strong reference to event during the call. */
GST_TRACER_PAD_PUSH_EVENT_PRE (pad, event);
GST_OBJECT_LOCK (pad);
/* Note that serialized events (and by extension, the events in the sticky
* event list of the pad) are meant to be pushed while holding the srcpad
* stream lock.
* A FLUSH_START may have been pushed within the unlocked period, which
* would set the pad flushing flag, but a FLUSH_STOP requires the stream
* lock. */
data->ret = gst_pad_push_event_unchecked (pad, gst_event_ref (event),
GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM);
GST_OBJECT_UNLOCK (pad);
GST_TRACER_PAD_PUSH_EVENT_POST (pad, data->ret >= GST_FLOW_OK);
GST_OBJECT_LOCK (pad);
if (data->ret == GST_FLOW_CUSTOM_SUCCESS_1)
data->ret = GST_FLOW_OK;
}
@ -4151,8 +4173,11 @@ push_sticky (GstPad * pad, PadEvent * ev, gpointer user_data)
return data->ret == GST_FLOW_OK;
}
/* check sticky events and push them when needed. should be called
* with pad LOCK */
/* Check the sticky event list of the pad and push all sticky events that
* have not been yet received by downstream and that aren't priority-ordered
* after the optional @event passed as argument.
*
* Must be called with pad LOCK. */
static inline GstFlowReturn
check_sticky (GstPad * pad, GstEvent * event)
{
@ -4175,10 +4200,21 @@ check_sticky (GstPad * pad, GstEvent * event)
PadEvent *ev = find_event_by_type (pad, GST_EVENT_EOS, 0);
if (ev && !ev->received) {
/* Store and ref the event *before* unlocking, as the PadEvent list
* may be modified during the unlocked period (e.g. by a flush or
* instant rate change event). */
GstEvent *event = gst_event_ref (ev->event);
GST_OBJECT_UNLOCK (pad);
GST_TRACER_PAD_PUSH_EVENT_PRE (pad, event);
data.ret = gst_pad_push_event_unchecked (pad, gst_event_ref (ev->event),
GST_OBJECT_LOCK (pad);
data.ret = gst_pad_push_event_unchecked (pad, event,
GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM);
GST_OBJECT_UNLOCK (pad);
GST_TRACER_PAD_PUSH_EVENT_POST (pad, data.ret >= GST_FLOW_OK);
GST_OBJECT_LOCK (pad);
/* the event could have been dropped. Because this can only
* happen if the user asked for it, it's not an error */
if (data.ret == GST_FLOW_CUSTOM_SUCCESS)
@ -5737,8 +5773,8 @@ idle_probe_stopped:
/**
* gst_pad_push_event:
* @pad: a #GstPad to push the event to.
* @event: (transfer full): the #GstEvent to send to the pad.
* @pad: the #GstPad that will push the event.
* @event: (transfer full): the #GstEvent to push out of the pad.
*
* Sends the event to the peer of the given pad. This function is
* mainly used by elements to send events to their peer