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basesrc: Don't hold LIVE_LOCK in create/alloc/fill

Browse source 
Holding this lock on live source prevents the source from changing
the caps in ::create() without risking a deadlock. This has consequences
as the LIVE_LOCK was replacing the STREAM_LOCK in many situation. As a
side effect:

- We no longer need to unlock when doing play/pause as the LIVE_LOCK
  isn't held. We then let the create() call finish, but will block if
  the state have changed meanwhile. This has the benefit that
  wait_preroll() calls in subclass is no longer needed.
- We no longer need to change the state to unlock, simplifying the
  set_flushing() interface
- We need different handling for EOS depending if we are in push or pull
  mode.

This patch also document the locking of each private class member and
the locking order.

https://bugzilla.gnome.org/show_bug.cgi?id=783301
This commit is contained in:
Nicolas Dufresne 2017-06-01 10:36:26 -04:00
parent 946622ec3f
commit 523de1a9dc
1 changed files with 180 additions and 153 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

333
libs/gst/base/gstbasesrc.c
View file

@ -204,59 +204,64 @@ enum
#define GST_BASE_SRC_GET_PRIVATE(obj) \
(G_TYPE_INSTANCE_GET_PRIVATE ((obj), GST_TYPE_BASE_SRC, GstBaseSrcPrivate))
/* The basesrc implementation need to respect the following locking order:
* 1. STREAM_LOCK
* 2. LIVE_LOCK
* 3. OBJECT_LOCK
*/
struct _GstBaseSrcPrivate
{
gboolean discont;
gboolean flushing;
gboolean discont; /* STREAM_LOCK */
gboolean flushing; /* LIVE_LOCK */
GstFlowReturn start_result;
gboolean async;
GstFlowReturn start_result; /* OBJECT_LOCK */
gboolean async; /* OBJECT_LOCK */
/* if a stream-start event should be sent */
gboolean stream_start_pending;
gboolean stream_start_pending; /* STREAM_LOCK */
/* if segment should be sent and a
* seqnum if it was originated by a seek */
gboolean segment_pending;
guint32 segment_seqnum;
gboolean segment_pending; /* OBJECT_LOCK */
guint32 segment_seqnum; /* OBJECT_LOCK */
/* if EOS is pending (atomic) */
GstEvent *pending_eos;
gint has_pending_eos;
GstEvent *pending_eos; /* OBJECT_LOCK */
gint has_pending_eos; /* atomic */
/* if the eos was caused by a forced eos from the application */
gboolean forced_eos;
gboolean forced_eos; /* LIVE_LOCK */
/* startup latency is the time it takes between going to PLAYING and producing
* the first BUFFER with running_time 0. This value is included in the latency
* reporting. */
GstClockTime latency;
GstClockTime latency; /* OBJECT_LOCK */
/* timestamp offset, this is the offset add to the values of gst_times for
* pseudo live sources */
GstClockTimeDiff ts_offset;
GstClockTimeDiff ts_offset; /* OBJECT_LOCK */
gboolean do_timestamp;
volatile gint dynamic_size;
volatile gint automatic_eos;
gboolean do_timestamp; /* OBJECT_LOCK */
volatile gint dynamic_size; /* atomic */
volatile gint automatic_eos; /* atomic */
/* stream sequence number */
guint32 seqnum;
guint32 seqnum; /* STREAM_LOCK */
/* pending events (TAG, CUSTOM_BOTH, CUSTOM_DOWNSTREAM) to be
* pushed in the data stream */
GList *pending_events;
volatile gint have_events;
GList *pending_events; /* OBJECT_LOCK */
volatile gint have_events; /* OBJECT_LOCK */
/* QoS *//* with LOCK */
gboolean qos_enabled;
gdouble proportion;
GstClockTime earliest_time;
gboolean qos_enabled; /* unused */
gdouble proportion; /* OBJECT_LOCK */
GstClockTime earliest_time; /* OBJECT_LOCK */
GstBufferPool *pool;
GstAllocator *allocator;
GstAllocationParams params;
GstBufferPool *pool; /* OBJECT_LOCK */
GstAllocator *allocator; /* OBJECT_LOCK */
GstAllocationParams params; /* OBJECT_LOCK */
GCond async_cond;
GCond async_cond; /* OBJECT_LOCK */
};
static GstElementClass *parent_class = NULL;
@ -328,7 +333,7 @@ static gboolean gst_base_src_decide_allocation_default (GstBaseSrc * basesrc,
GstQuery * query);
static gboolean gst_base_src_set_flushing (GstBaseSrc * basesrc,
gboolean flushing, gboolean live_play, gboolean * playing);
gboolean flushing);
static gboolean gst_base_src_start (GstBaseSrc * basesrc);
static gboolean gst_base_src_stop (GstBaseSrc * basesrc);
@ -484,6 +489,31 @@ gst_base_src_finalize (GObject * object)
G_OBJECT_CLASS (parent_class)->finalize (object);
}
/* Call with LIVE_LOCK held */
static GstFlowReturn
gst_base_src_wait_playing_unlocked (GstBaseSrc * src)
{
while (G_UNLIKELY (!src->live_running && !src->priv->flushing)) {
/* block until the state changes, or we get a flush, or something */
GST_DEBUG_OBJECT (src, "live source waiting for running state");
GST_LIVE_WAIT (src);
GST_DEBUG_OBJECT (src, "live source unlocked");
}
if (src->priv->flushing)
goto flushing;
return GST_FLOW_OK;
/* ERRORS */
flushing:
{
GST_DEBUG_OBJECT (src, "we are flushing");
return GST_FLOW_FLUSHING;
}
}
/**
* gst_base_src_wait_playing:
* @src: the src
@ -503,25 +533,15 @@ gst_base_src_finalize (GObject * object)
GstFlowReturn
gst_base_src_wait_playing (GstBaseSrc * src)
{
GstFlowReturn ret;
g_return_val_if_fail (GST_IS_BASE_SRC (src), GST_FLOW_ERROR);
do {
/* block until the state changes, or we get a flush, or something */
GST_DEBUG_OBJECT (src, "live source waiting for running state");
GST_LIVE_WAIT (src);
GST_DEBUG_OBJECT (src, "live source unlocked");
if (src->priv->flushing)
goto flushing;
} while (G_UNLIKELY (!src->live_running));
GST_LIVE_LOCK (src);
ret = gst_base_src_wait_playing_unlocked (src);
GST_LIVE_UNLOCK (src);
return GST_FLOW_OK;
/* ERRORS */
flushing:
{
GST_DEBUG_OBJECT (src, "we are flushing");
return GST_FLOW_FLUSHING;
}
return ret;
}
/**
@ -855,6 +875,7 @@ gst_base_src_new_seamless_segment (GstBaseSrc * src, gint64 start, gint64 stop,
return res;
}
/* called with STREAM_LOCK */
static gboolean
gst_base_src_send_stream_start (GstBaseSrc * src)
{
@ -1577,7 +1598,7 @@ gst_base_src_perform_seek (GstBaseSrc * src, GstEvent * event, gboolean unlock)
GstSeekFlags flags;
GstSeekType start_type, stop_type;
gint64 start, stop;
gboolean flush, playing;
gboolean flush;
gboolean update;
gboolean relative_seek = FALSE;
gboolean seekseg_configured = FALSE;
@ -1629,7 +1650,7 @@ gst_base_src_perform_seek (GstBaseSrc * src, GstEvent * event, gboolean unlock)
/* unblock streaming thread. */
if (unlock)
gst_base_src_set_flushing (src, TRUE, FALSE, &playing);
gst_base_src_set_flushing (src, TRUE);
/* grab streaming lock, this should eventually be possible, either
* because the task is paused, our streaming thread stopped
@ -1645,7 +1666,7 @@ gst_base_src_perform_seek (GstBaseSrc * src, GstEvent * event, gboolean unlock)
}
if (unlock)
gst_base_src_set_flushing (src, FALSE, playing, NULL);
gst_base_src_set_flushing (src, FALSE);
/* If we configured the seeksegment above, don't overwrite it now. Otherwise
* copy the current segment info into the temp segment that we can actually
@ -1762,51 +1783,30 @@ gst_base_src_send_event (GstElement * element, GstEvent * event)
/* bidirectional events */
case GST_EVENT_FLUSH_START:
GST_DEBUG_OBJECT (src, "pushing flush-start event downstream");
result = gst_pad_push_event (src->srcpad, event);
/* also unblock the create function */
gst_base_src_activate_pool (src, FALSE);
/* unlock any subclasses, we need to do this before grabbing the
* LIVE_LOCK since we hold this lock before going into ::create. We pass an
* unlock to the params because of backwards compat (see seek handler)*/
if (bclass->unlock)
bclass->unlock (src);
/* the live lock is released when we are blocked, waiting for playing or
* when we sync to the clock. */
GST_LIVE_LOCK (src);
src->priv->flushing = TRUE;
/* clear pending EOS if any */
if (g_atomic_int_get (&src->priv->has_pending_eos)) {
GST_OBJECT_LOCK (src);
CLEAR_PENDING_EOS (src);
src->priv->forced_eos = FALSE;
GST_OBJECT_UNLOCK (src);
}
if (bclass->unlock_stop)
bclass->unlock_stop (src);
if (src->clock_id)
gst_clock_id_unschedule (src->clock_id);
GST_DEBUG_OBJECT (src, "signal");
GST_LIVE_SIGNAL (src);
GST_LIVE_UNLOCK (src);
result = gst_pad_push_event (src->srcpad, event);
gst_base_src_set_flushing (src, TRUE);
event = NULL;
break;
case GST_EVENT_FLUSH_STOP:
{
gboolean start;
GST_LIVE_LOCK (src);
src->priv->segment_pending = TRUE;
src->priv->flushing = FALSE;
GST_PAD_STREAM_LOCK (src->srcpad);
gst_base_src_set_flushing (src, FALSE);
GST_DEBUG_OBJECT (src, "pushing flush-stop event downstream");
result = gst_pad_push_event (src->srcpad, event);
gst_base_src_activate_pool (src, TRUE);
/* For external flush, restart the task .. */
GST_LIVE_LOCK (src);
src->priv->segment_pending = TRUE;
GST_OBJECT_LOCK (src->srcpad);
start = (GST_PAD_MODE (src->srcpad) == GST_PAD_MODE_PUSH);
GST_OBJECT_UNLOCK (src->srcpad);
/* ... and for live sources, only if in playing state */
if (src->is_live) {
if (!src->live_running)
start = FALSE;
@ -1815,7 +1815,10 @@ gst_base_src_send_event (GstElement * element, GstEvent * event)
if (start)
gst_pad_start_task (src->srcpad, (GstTaskFunction) gst_base_src_loop,
src->srcpad, NULL);
GST_LIVE_UNLOCK (src);
GST_PAD_STREAM_UNLOCK (src->srcpad);
event = NULL;
break;
}
@ -1823,47 +1826,68 @@ gst_base_src_send_event (GstElement * element, GstEvent * event)
/* downstream serialized events */
case GST_EVENT_EOS:
{
gboolean push_mode;
/* queue EOS and make sure the task or pull function performs the EOS
* actions.
*
* We have two possibilities:
* For push mode, This will be done in 3 steps. It is required to not
* block here as gst_element_send_event() will hold the STATE_LOCK, hence
* blocking would prevent asynchronous state change to complete.
*
* - Before we are to enter the _create function, we check the has_pending_eos
* first and do EOS instead of entering it.
* - If we are in the _create function or we did not manage to set the
* flag fast enough and we are about to enter the _create function,
* we unlock it so that we exit with FLUSHING immediately. We then
* check the EOS flag and do the EOS logic.
* 1. We stop the streaming thread
* 2. We set the pending eos
* 3. We start the streaming thread again, so it is performed
* asynchronously.
*
* For pull mode, we simply mark the pending EOS without flushing.
*/
GST_OBJECT_LOCK (src);
g_atomic_int_set (&src->priv->has_pending_eos, TRUE);
if (src->priv->pending_eos)
gst_event_unref (src->priv->pending_eos);
src->priv->pending_eos = event;
GST_OBJECT_LOCK (src->srcpad);
push_mode = GST_PAD_MODE (src->srcpad) == GST_PAD_MODE_PUSH;
GST_OBJECT_UNLOCK (src->srcpad);
if (push_mode) {
gst_base_src_set_flushing (src, TRUE);
GST_PAD_STREAM_LOCK (src->srcpad);
gst_base_src_set_flushing (src, FALSE);
GST_OBJECT_LOCK (src);
g_atomic_int_set (&src->priv->has_pending_eos, TRUE);
if (src->priv->pending_eos)
gst_event_unref (src->priv->pending_eos);
src->priv->pending_eos = event;
GST_OBJECT_UNLOCK (src);
GST_DEBUG_OBJECT (src,
"EOS marked, start task for asynchronous handling");
gst_pad_start_task (src->srcpad, (GstTaskFunction) gst_base_src_loop,
src->srcpad, NULL);
GST_PAD_STREAM_UNLOCK (src->srcpad);
} else {
/* In pull mode, we need not to return flushing to downstream, though
* the stream lock is not kept after getrange was unblocked */
GST_OBJECT_LOCK (src);
g_atomic_int_set (&src->priv->has_pending_eos, TRUE);
if (src->priv->pending_eos)
gst_event_unref (src->priv->pending_eos);
src->priv->pending_eos = event;
GST_OBJECT_UNLOCK (src);
gst_base_src_activate_pool (src, FALSE);
if (bclass->unlock)
bclass->unlock (src);
GST_PAD_STREAM_LOCK (src->srcpad);
if (bclass->unlock_stop)
bclass->unlock_stop (src);
GST_PAD_STREAM_UNLOCK (src->srcpad);
}
event = NULL;
GST_OBJECT_UNLOCK (src);
GST_DEBUG_OBJECT (src, "EOS marked, calling unlock");
/* unlock the _create function so that we can check the has_pending_eos flag
* and we can do EOS. This will eventually release the LIVE_LOCK again so
* that we can grab it and stop the unlock again. We don't take the stream
* lock so that this operation is guaranteed to never block. */
gst_base_src_activate_pool (src, FALSE);
if (bclass->unlock)
bclass->unlock (src);
GST_DEBUG_OBJECT (src, "unlock called, waiting for LIVE_LOCK");
GST_LIVE_LOCK (src);
GST_DEBUG_OBJECT (src, "LIVE_LOCK acquired, calling unlock_stop");
/* now stop the unlock of the streaming thread again. Grabbing the live
* lock is enough because that protects the create function. */
if (bclass->unlock_stop)
bclass->unlock_stop (src);
gst_base_src_activate_pool (src, TRUE);
GST_LIVE_UNLOCK (src);
result = TRUE;
break;
}
@ -2005,10 +2029,10 @@ gst_base_src_default_event (GstBaseSrc * src, GstEvent * event)
case GST_EVENT_FLUSH_START:
/* cancel any blocking getrange, is normally called
* when in pull mode. */
result = gst_base_src_set_flushing (src, TRUE, FALSE, NULL);
result = gst_base_src_set_flushing (src, TRUE);
break;
case GST_EVENT_FLUSH_STOP:
result = gst_base_src_set_flushing (src, FALSE, TRUE, NULL);
result = gst_base_src_set_flushing (src, FALSE);
break;
case GST_EVENT_QOS:
{
@ -2427,7 +2451,7 @@ gst_base_src_get_range (GstBaseSrc * src, guint64 offset, guint length,
again:
if (src->is_live) {
if (G_UNLIKELY (!src->live_running)) {
ret = gst_base_src_wait_playing (src);
ret = gst_base_src_wait_playing_unlocked (src);
if (ret != GST_FLOW_OK)
goto stopped;
}
@ -2470,7 +2494,23 @@ again:
res_buf = in_buf = *buf;
GST_LIVE_UNLOCK (src);
ret = bclass->create (src, offset, length, &res_buf);
GST_LIVE_LOCK (src);
/* As we released the LIVE_LOCK, the state may have changed */
if (src->is_live) {
if (G_UNLIKELY (!src->live_running)) {
GstFlowReturn wait_ret;
wait_ret = gst_base_src_wait_playing_unlocked (src);
if (wait_ret != GST_FLOW_OK) {
if (ret == GST_FLOW_OK && *buf == NULL)
gst_buffer_unref (res_buf);
ret = wait_ret;
goto stopped;
}
}
}
/* The create function could be unlocked because we have a pending EOS. It's
* possible that we have a valid buffer from create that we need to
@ -2677,6 +2717,7 @@ start_failed:
}
}
/* Called with STREAM_LOCK */
static void
gst_base_src_loop (GstPad * pad)
{
@ -2698,6 +2739,14 @@ gst_base_src_loop (GstPad * pad)
goto flushing;
GST_LIVE_UNLOCK (src);
/* Just return if EOS is pushed again, as the app might be unaware that an
* EOS have been sent already */
if (GST_PAD_IS_EOS (pad)) {
GST_DEBUG_OBJECT (src, "Pad is marked as EOS, pause the task");
gst_pad_pause_task (pad);
goto done;
}
gst_base_src_send_stream_start (src);
/* The stream-start event could've caused something to flush us */
@ -3427,7 +3476,7 @@ gst_base_src_start_complete (GstBaseSrc * basesrc, GstFlowReturn ret)
/* stop flushing now but for live sources, still block in the LIVE lock when
* we are not yet PLAYING */
gst_base_src_set_flushing (basesrc, FALSE, FALSE, NULL);
gst_base_src_set_flushing (basesrc, FALSE);
gst_pad_mark_reconfigure (GST_BASE_SRC_PAD (basesrc));
@ -3546,7 +3595,7 @@ gst_base_src_stop (GstBaseSrc * basesrc)
GST_DEBUG_OBJECT (basesrc, "stopping source");
/* flush all */
gst_base_src_set_flushing (basesrc, TRUE, FALSE, NULL);
gst_base_src_set_flushing (basesrc, TRUE);
/* stop the task */
gst_pad_stop_task (basesrc->srcpad);
@ -3579,34 +3628,26 @@ was_stopped:
/* start or stop flushing dataprocessing
*/
static gboolean
gst_base_src_set_flushing (GstBaseSrc * basesrc,
gboolean flushing, gboolean live_play, gboolean * playing)
gst_base_src_set_flushing (GstBaseSrc * basesrc, gboolean flushing)
{
GstBaseSrcClass *bclass;
bclass = GST_BASE_SRC_GET_CLASS (basesrc);
GST_DEBUG_OBJECT (basesrc, "flushing %d, live_play %d", flushing, live_play);
GST_DEBUG_OBJECT (basesrc, "flushing %d", flushing);
if (flushing) {
gst_base_src_activate_pool (basesrc, FALSE);
/* unlock any subclasses, we need to do this before grabbing the
* LIVE_LOCK since we hold this lock before going into ::create. We pass an
* unlock to the params because of backwards compat (see seek handler)*/
/* unlock any subclasses to allow turning off the streaming thread */
if (bclass->unlock)
bclass->unlock (basesrc);
}
/* the live lock is released when we are blocked, waiting for playing or
* when we sync to the clock. */
/* the live lock is released when we are blocked, waiting for playing,
* when we sync to the clock or creating a buffer */
GST_LIVE_LOCK (basesrc);
if (playing)
*playing = basesrc->live_running;
basesrc->priv->flushing = flushing;
if (flushing) {
/* if we are locked in the live lock, signal it to make it flush */
basesrc->live_running = TRUE;
/* clear pending EOS if any */
if (g_atomic_int_get (&basesrc->priv->has_pending_eos)) {
GST_OBJECT_LOCK (basesrc);
@ -3615,17 +3656,10 @@ gst_base_src_set_flushing (GstBaseSrc * basesrc,
GST_OBJECT_UNLOCK (basesrc);
}
/* step 1, now that we have the LIVE lock, clear our unlock request */
if (bclass->unlock_stop)
bclass->unlock_stop (basesrc);
/* step 2, unblock clock sync (if any) or any other blocking thing */
/* unblock clock sync (if any) or any other blocking thing */
if (basesrc->clock_id)
gst_clock_id_unschedule (basesrc->clock_id);
} else {
/* signal the live source that it can start playing */
basesrc->live_running = live_play;
gst_base_src_activate_pool (basesrc, TRUE);
/* Drop all delayed events */
@ -3639,9 +3673,18 @@ gst_base_src_set_flushing (GstBaseSrc * basesrc,
}
GST_OBJECT_UNLOCK (basesrc);
}
GST_LIVE_SIGNAL (basesrc);
GST_LIVE_UNLOCK (basesrc);
if (!flushing) {
/* Now wait for the stream lock to be released and clear our unlock request */
GST_PAD_STREAM_LOCK (basesrc->srcpad);
if (bclass->unlock_stop)
bclass->unlock_stop (basesrc);
GST_PAD_STREAM_UNLOCK (basesrc->srcpad);
}
return TRUE;
}
@ -3650,17 +3693,6 @@ gst_base_src_set_flushing (GstBaseSrc * basesrc,
static gboolean
gst_base_src_set_playing (GstBaseSrc * basesrc, gboolean live_play)
{
GstBaseSrcClass *bclass;
bclass = GST_BASE_SRC_GET_CLASS (basesrc);
/* unlock subclasses locked in ::create, we only do this when we stop playing. */
if (!live_play) {
GST_DEBUG_OBJECT (basesrc, "unlock");
if (bclass->unlock)
bclass->unlock (basesrc);
}
/* we are now able to grab the LIVE lock, when we get it, we can be
* waiting for PLAYING while blocked in the LIVE cond or we can be waiting
* for the clock. */
@ -3678,11 +3710,6 @@ gst_base_src_set_playing (GstBaseSrc * basesrc, gboolean live_play)
if (live_play) {
gboolean start;
/* clear our unlock request when going to PLAYING */
GST_DEBUG_OBJECT (basesrc, "unlock stop");
if (bclass->unlock_stop)
bclass->unlock_stop (basesrc);
/* for live sources we restart the timestamp correction */
GST_OBJECT_LOCK (basesrc);
basesrc->priv->latency = -1;
@ -3840,7 +3867,7 @@ gst_base_src_change_state (GstElement * element, GstStateChange transition)
case GST_STATE_CHANGE_PLAYING_TO_PAUSED:
GST_DEBUG_OBJECT (basesrc, "PLAYING->PAUSED");
if (gst_base_src_is_live (basesrc)) {
/* make sure we block in the live lock in PAUSED */
/* make sure we block in the live cond in PAUSED */
gst_base_src_set_playing (basesrc, FALSE);
no_preroll = TRUE;
}