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Original commit message from CVS: * gst/gstsystemclock.c: (gst_system_clock_id_wait_jitter_unlocked): Add some more docs to explain why a FIXME was wrongly added.
554 lines
18 KiB
C
554 lines
18 KiB
C
/* GStreamer
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* Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
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* 2004 Wim Taymans <wim@fluendo.com>
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*
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* gstsystemclock.c: Default clock, uses the system clock
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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/**
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* SECTION:gstsystemclock
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* @short_description: Default clock that uses the current system time
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* @see_also: #GstClock
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*
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* The GStreamer core provides a GstSystemClock based on the system time.
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* Asynchronous callbacks are scheduled from an internal thread.
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*
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* Clock implementors are encouraged to subclass this systemclock as it
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* implements the async notification.
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*
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* Subclasses can however override all of the important methods for sync and
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* async notifications to implement their own callback methods or blocking
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* wait operations.
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*
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* Last reviewed on 2006-03-08 (0.10.4)
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*/
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#include "gst_private.h"
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#include "gstinfo.h"
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#include "gstsystemclock.h"
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/* Define this to get some extra debug about jitter from each clock_wait */
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#undef WAIT_DEBUGGING
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/* the one instance of the systemclock */
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static GstClock *_the_system_clock = NULL;
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static void gst_system_clock_class_init (GstSystemClockClass * klass);
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static void gst_system_clock_init (GstSystemClock * clock);
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static void gst_system_clock_dispose (GObject * object);
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static GstClockTime gst_system_clock_get_internal_time (GstClock * clock);
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static guint64 gst_system_clock_get_resolution (GstClock * clock);
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static GstClockReturn gst_system_clock_id_wait_jitter (GstClock * clock,
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GstClockEntry * entry, GstClockTimeDiff * jitter);
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static GstClockReturn gst_system_clock_id_wait_jitter_unlocked
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(GstClock * clock, GstClockEntry * entry, GstClockTimeDiff * jitter,
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gboolean restart);
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static GstClockReturn gst_system_clock_id_wait_async (GstClock * clock,
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GstClockEntry * entry);
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static void gst_system_clock_id_unschedule (GstClock * clock,
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GstClockEntry * entry);
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static void gst_system_clock_async_thread (GstClock * clock);
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static gboolean gst_system_clock_start_async (GstSystemClock * clock);
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static GStaticMutex _gst_sysclock_mutex = G_STATIC_MUTEX_INIT;
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static GstClockClass *parent_class = NULL;
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/* static guint gst_system_clock_signals[LAST_SIGNAL] = { 0 }; */
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GType
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gst_system_clock_get_type (void)
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{
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static GType clock_type = 0;
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if (G_UNLIKELY (clock_type == 0)) {
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static const GTypeInfo clock_info = {
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sizeof (GstSystemClockClass),
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NULL,
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NULL,
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(GClassInitFunc) gst_system_clock_class_init,
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NULL,
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NULL,
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sizeof (GstSystemClock),
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0,
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(GInstanceInitFunc) gst_system_clock_init,
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NULL
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};
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clock_type = g_type_register_static (GST_TYPE_CLOCK, "GstSystemClock",
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&clock_info, 0);
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}
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return clock_type;
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}
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static void
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gst_system_clock_class_init (GstSystemClockClass * klass)
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{
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GObjectClass *gobject_class;
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GstObjectClass *gstobject_class;
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GstClockClass *gstclock_class;
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gobject_class = (GObjectClass *) klass;
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gstobject_class = (GstObjectClass *) klass;
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gstclock_class = (GstClockClass *) klass;
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parent_class = g_type_class_peek_parent (klass);
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gobject_class->dispose = gst_system_clock_dispose;
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gstclock_class->get_internal_time = gst_system_clock_get_internal_time;
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gstclock_class->get_resolution = gst_system_clock_get_resolution;
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gstclock_class->wait_jitter = gst_system_clock_id_wait_jitter;
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gstclock_class->wait_async = gst_system_clock_id_wait_async;
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gstclock_class->unschedule = gst_system_clock_id_unschedule;
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}
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static void
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gst_system_clock_init (GstSystemClock * clock)
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{
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GST_OBJECT_FLAG_SET (clock,
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GST_CLOCK_FLAG_CAN_DO_SINGLE_SYNC |
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GST_CLOCK_FLAG_CAN_DO_SINGLE_ASYNC |
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GST_CLOCK_FLAG_CAN_DO_PERIODIC_SYNC |
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GST_CLOCK_FLAG_CAN_DO_PERIODIC_ASYNC);
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#if 0
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/* Uncomment this to start the async clock thread straight away */
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GST_CLOCK_LOCK (clock);
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gst_system_clock_start_async (clock);
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GST_CLOCK_UNLOCK (clock);
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#endif
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}
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static void
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gst_system_clock_dispose (GObject * object)
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{
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GstClock *clock = (GstClock *) object;
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GstSystemClock *sysclock = GST_SYSTEM_CLOCK (clock);
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GList *entries;
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/* else we have to stop the thread */
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GST_OBJECT_LOCK (clock);
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sysclock->stopping = TRUE;
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/* unschedule all entries */
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for (entries = clock->entries; entries; entries = g_list_next (entries)) {
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GstClockEntry *entry = (GstClockEntry *) entries->data;
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GST_CAT_DEBUG (GST_CAT_CLOCK, "unscheduling entry %p", entry);
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entry->status = GST_CLOCK_UNSCHEDULED;
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}
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g_list_free (clock->entries);
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clock->entries = NULL;
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GST_CLOCK_BROADCAST (clock);
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GST_OBJECT_UNLOCK (clock);
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if (sysclock->thread)
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g_thread_join (sysclock->thread);
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sysclock->thread = NULL;
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GST_CAT_DEBUG (GST_CAT_CLOCK, "joined thread");
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G_OBJECT_CLASS (parent_class)->dispose (object);
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if (_the_system_clock == clock) {
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_the_system_clock = NULL;
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GST_CAT_DEBUG (GST_CAT_CLOCK, "disposed system clock");
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}
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}
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/**
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* gst_system_clock_obtain:
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*
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* Get a handle to the default system clock. The refcount of the
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* clock will be increased so you need to unref the clock after
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* usage.
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*
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* Returns: the default clock.
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*
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* MT safe.
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*/
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GstClock *
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gst_system_clock_obtain (void)
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{
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GstClock *clock;
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g_static_mutex_lock (&_gst_sysclock_mutex);
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clock = _the_system_clock;
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if (clock == NULL) {
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GST_CAT_DEBUG (GST_CAT_CLOCK, "creating new static system clock");
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clock = g_object_new (GST_TYPE_SYSTEM_CLOCK,
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"name", "GstSystemClock", NULL);
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/* we created the global clock; take ownership so
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* we can hand out instances later */
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gst_object_ref (clock);
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gst_object_sink (GST_OBJECT (clock));
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_the_system_clock = clock;
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g_static_mutex_unlock (&_gst_sysclock_mutex);
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} else {
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g_static_mutex_unlock (&_gst_sysclock_mutex);
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GST_CAT_DEBUG (GST_CAT_CLOCK, "returning static system clock");
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}
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/* we ref it since we are a clock factory. */
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gst_object_ref (clock);
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return clock;
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}
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/* this thread reads the sorted clock entries from the queue.
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*
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* It waits on each of them and fires the callback when the timeout occurs.
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*
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* When an entry in the queue was canceled before we wait for it, it is
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* simply skipped.
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*
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* When waiting for an entry, it can become canceled, in that case we don't
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* call the callback but move to the next item in the queue.
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*
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* MT safe.
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*/
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static void
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gst_system_clock_async_thread (GstClock * clock)
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{
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GstSystemClock *sysclock = GST_SYSTEM_CLOCK (clock);
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GST_CAT_DEBUG (GST_CAT_CLOCK, "enter system clock thread");
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GST_OBJECT_LOCK (clock);
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/* signal spinup */
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GST_CLOCK_BROADCAST (clock);
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/* now enter our (almost) infinite loop */
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while (!sysclock->stopping) {
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GstClockEntry *entry;
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GstClockTime requested;
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GstClockReturn res;
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/* check if something to be done */
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while (clock->entries == NULL) {
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GST_CAT_DEBUG (GST_CAT_CLOCK, "no clock entries, waiting..");
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/* wait for work to do */
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GST_CLOCK_WAIT (clock);
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GST_CAT_DEBUG (GST_CAT_CLOCK, "got signal");
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/* clock was stopping, exit */
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if (sysclock->stopping)
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goto exit;
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}
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/* pick the next entry */
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entry = clock->entries->data;
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/* if it was unscheduled, just move on to the next entry */
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if (entry->status == GST_CLOCK_UNSCHEDULED) {
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GST_CAT_DEBUG (GST_CAT_CLOCK, "entry %p was unscheduled", entry);
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goto next_entry;
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}
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requested = entry->time;
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/* now wait for the entry, we already hold the lock */
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res =
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gst_system_clock_id_wait_jitter_unlocked (clock, (GstClockID) entry,
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NULL, FALSE);
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switch (res) {
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case GST_CLOCK_UNSCHEDULED:
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/* entry was unscheduled, move to the next */
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GST_CAT_DEBUG (GST_CAT_CLOCK, "async entry %p unscheduled", entry);
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goto next_entry;
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case GST_CLOCK_OK:
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case GST_CLOCK_EARLY:
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{
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/* entry timed out normally, fire the callback and move to the next
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* entry */
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GST_CAT_DEBUG (GST_CAT_CLOCK, "async entry %p unlocked", entry);
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if (entry->func) {
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/* unlock before firing the callback */
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GST_OBJECT_UNLOCK (clock);
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entry->func (clock, entry->time, (GstClockID) entry,
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entry->user_data);
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GST_OBJECT_LOCK (clock);
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}
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if (entry->type == GST_CLOCK_ENTRY_PERIODIC) {
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/* adjust time now */
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entry->time = requested + entry->interval;
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/* and resort the list now */
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clock->entries =
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g_list_sort (clock->entries, gst_clock_id_compare_func);
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/* and restart */
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continue;
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} else {
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goto next_entry;
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}
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}
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case GST_CLOCK_BUSY:
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/* somebody unlocked the entry but is was not canceled, This means that
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* either a new entry was added in front of the queue or some other entry
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* was canceled. Whatever it is, pick the head entry of the list and
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* continue waiting. */
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GST_CAT_DEBUG (GST_CAT_CLOCK, "async entry %p needs restart", entry);
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continue;
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default:
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GST_CAT_DEBUG (GST_CAT_CLOCK,
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"strange result %d waiting for %p, skipping", res, entry);
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g_warning ("%s: strange result %d waiting for %p, skipping",
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GST_OBJECT_NAME (clock), res, entry);
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goto next_entry;
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}
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next_entry:
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/* we remove the current entry and unref it */
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clock->entries = g_list_remove (clock->entries, entry);
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gst_clock_id_unref ((GstClockID) entry);
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}
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exit:
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/* signal exit */
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GST_CLOCK_BROADCAST (clock);
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GST_OBJECT_UNLOCK (clock);
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GST_CAT_DEBUG (GST_CAT_CLOCK, "exit system clock thread");
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}
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/* MT safe */
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static GstClockTime
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gst_system_clock_get_internal_time (GstClock * clock)
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{
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GTimeVal timeval;
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g_get_current_time (&timeval);
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return GST_TIMEVAL_TO_TIME (timeval);
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}
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static guint64
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gst_system_clock_get_resolution (GstClock * clock)
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{
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return 1 * GST_USECOND;
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}
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/* synchronously wait on the given GstClockEntry.
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*
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* We do this by blocking on the global clock GCond variable with
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* the requested time as a timeout. This allows us to unblock the
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* entry by signaling the GCond variable.
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*
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* Note that signaling the global GCond unlocks all waiting entries. So
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* we need to check if an unlocked entry has changed when it unlocks.
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*
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* Entries that arrive too late are simply not waited on and a
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* GST_CLOCK_EARLY result is returned.
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*
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* should be called with LOCK held.
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*
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* MT safe.
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*/
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static GstClockReturn
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gst_system_clock_id_wait_jitter_unlocked (GstClock * clock,
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GstClockEntry * entry, GstClockTimeDiff * jitter, gboolean restart)
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{
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GstClockTime entryt, real, now, target;
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GstClockTimeDiff diff;
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/* need to call the overridden method because we want to sync against the time
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* of the clock, whatever the subclass uses as a clock. */
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real = GST_CLOCK_GET_CLASS (clock)->get_internal_time (clock);
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entryt = GST_CLOCK_ENTRY_TIME (entry);
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now = gst_clock_adjust_unlocked (clock, real);
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if (jitter) {
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*jitter = GST_CLOCK_DIFF (entryt, now);
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}
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/* the diff of the entry with the clock is the amount of time we have to
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* wait */
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diff = entryt - now;
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/* Our GCond implementation expects an absolute time against the system clock
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* as a timeout value. We use our internal time to get the system time and add
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* the expected timeout to it, this gives us the absolute time of the
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* timeout. */
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target = gst_system_clock_get_internal_time (clock) + diff;
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GST_CAT_DEBUG (GST_CAT_CLOCK, "entry %p"
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" target %" GST_TIME_FORMAT
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" entry %" GST_TIME_FORMAT
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" now %" GST_TIME_FORMAT
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" real %" GST_TIME_FORMAT
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" diff (entry-now) %" G_GINT64_FORMAT,
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entry,
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GST_TIME_ARGS (target),
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GST_TIME_ARGS (entryt), GST_TIME_ARGS (now), GST_TIME_ARGS (real), diff);
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if (diff > 0) {
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GTimeVal tv;
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#ifdef WAIT_DEBUGGING
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GstClockTime result, final;
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#endif
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GST_TIME_TO_TIMEVAL (target, tv);
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while (TRUE) {
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/* now wait on the entry, it either times out or the cond is signaled. */
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if (!GST_CLOCK_TIMED_WAIT (clock, &tv)) {
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/* timeout, this is fine, we can report success now */
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GST_CAT_DEBUG (GST_CAT_CLOCK, "entry %p unlocked after timeout", entry);
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entry->status = GST_CLOCK_OK;
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#ifdef WAIT_DEBUGGING
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real = GST_CLOCK_GET_CLASS (clock)->get_internal_time (clock);
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result = gst_clock_adjust_unlocked (clock, real);
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final = gst_system_clock_get_internal_time (clock);
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GST_CAT_DEBUG (GST_CAT_CLOCK, "Waited for %" G_GINT64_FORMAT
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" got %" G_GINT64_FORMAT " diff %" G_GINT64_FORMAT
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" %g target-offset %" G_GINT64_FORMAT " %g", entryt, result,
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result - entryt,
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(double) (GstClockTimeDiff) (result - entryt) / GST_SECOND,
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(final - target),
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((double) (GstClockTimeDiff) (final - target)) / GST_SECOND);
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#endif
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break;
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} else {
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/* the waiting is interrupted because the GCond was signaled. This can
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* be because this or some other entry was unscheduled. */
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GST_CAT_DEBUG (GST_CAT_CLOCK, "entry %p unlocked with signal", entry);
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/* if the entry is unscheduled, we can stop waiting for it, else we
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* continue our while loop. */
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if (entry->status == GST_CLOCK_UNSCHEDULED)
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break;
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/* else restart if we must */
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if (!restart)
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break;
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/* this can happen if the entry got unlocked because of an async entry
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* was added to the head of the async queue. */
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GST_CAT_DEBUG (GST_CAT_CLOCK, "continue waiting for entry %p", entry);
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}
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}
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} else if (diff == 0) {
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entry->status = GST_CLOCK_OK;
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} else {
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entry->status = GST_CLOCK_EARLY;
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}
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return entry->status;
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}
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static GstClockReturn
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gst_system_clock_id_wait_jitter (GstClock * clock, GstClockEntry * entry,
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GstClockTimeDiff * jitter)
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{
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GstClockReturn ret;
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GST_OBJECT_LOCK (clock);
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ret = gst_system_clock_id_wait_jitter_unlocked (clock, entry, jitter, TRUE);
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GST_OBJECT_UNLOCK (clock);
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return ret;
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}
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/* Start the async clock thread. Must be called with the object lock
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* held */
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static gboolean
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gst_system_clock_start_async (GstSystemClock * clock)
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{
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GError *error = NULL;
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if (clock->thread != NULL)
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return TRUE; /* Thread already running. Nothing to do */
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clock->thread = g_thread_create ((GThreadFunc) gst_system_clock_async_thread,
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clock, TRUE, &error);
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if (error)
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goto no_thread;
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/* wait for it to spin up */
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GST_CLOCK_WAIT (clock);
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return TRUE;
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/* ERRORS */
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no_thread:
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{
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g_warning ("could not create async clock thread: %s", error->message);
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}
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return FALSE;
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}
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/* Add an entry to the list of pending async waits. The entry is inserted
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|
* in sorted order. If we inserted the entry at the head of the list, we
|
|
* need to signal the thread as it might either be waiting on it or waiting
|
|
* for a new entry.
|
|
*
|
|
* MT safe.
|
|
*/
|
|
static GstClockReturn
|
|
gst_system_clock_id_wait_async (GstClock * clock, GstClockEntry * entry)
|
|
{
|
|
GST_CAT_DEBUG (GST_CAT_CLOCK, "adding async entry %p", entry);
|
|
|
|
GST_OBJECT_LOCK (clock);
|
|
|
|
/* Start the clock async thread if needed */
|
|
if (!gst_system_clock_start_async (GST_SYSTEM_CLOCK (clock)))
|
|
goto thread_error;
|
|
|
|
/* need to take a ref */
|
|
gst_clock_id_ref ((GstClockID) entry);
|
|
/* insert the entry in sorted order */
|
|
clock->entries = g_list_insert_sorted (clock->entries, entry,
|
|
gst_clock_id_compare_func);
|
|
|
|
/* only need to send the signal if the entry was added to the
|
|
* front, else the thread is just waiting for another entry and
|
|
* will get to this entry automatically. */
|
|
if (clock->entries->data == entry) {
|
|
GST_CAT_DEBUG (GST_CAT_CLOCK, "async entry added to head, sending signal");
|
|
/* this will wake up _all_ entries waiting for the clock because we have
|
|
* only one cond for all entries (makes allocation faster). Entries that
|
|
* have not timed out will have their status set to BUSY and should continue
|
|
* to wait. In the case of the async ones, the new head entry should be
|
|
* taken and waited for. */
|
|
GST_CLOCK_BROADCAST (clock);
|
|
}
|
|
GST_OBJECT_UNLOCK (clock);
|
|
|
|
return GST_CLOCK_OK;
|
|
|
|
thread_error:
|
|
/* Could not start the async clock thread */
|
|
return GST_CLOCK_ERROR;
|
|
}
|
|
|
|
/* unschedule an entry. This will set the state of the entry to GST_CLOCK_UNSCHEDULED
|
|
* and will signal any thread waiting for entries to recheck their entry.
|
|
* We cannot really decide if the signal is needed or not because the entry
|
|
* could be waited on in async or sync mode.
|
|
*
|
|
* MT safe.
|
|
*/
|
|
static void
|
|
gst_system_clock_id_unschedule (GstClock * clock, GstClockEntry * entry)
|
|
{
|
|
GST_CAT_DEBUG (GST_CAT_CLOCK, "unscheduling entry %p", entry);
|
|
|
|
GST_OBJECT_LOCK (clock);
|
|
/* mark entry as unscheduled, then wake up all entries. The entries that did
|
|
* not timeout will be woken up but immediatly go to sleep again because their
|
|
* status would still be busy. */
|
|
entry->status = GST_CLOCK_UNSCHEDULED;
|
|
GST_CAT_DEBUG (GST_CAT_CLOCK, "sending signal");
|
|
GST_CLOCK_BROADCAST (clock);
|
|
GST_OBJECT_UNLOCK (clock);
|
|
}
|