mirror of
https://gitlab.freedesktop.org/gstreamer/gstreamer.git
synced 2024-12-24 09:10:36 +00:00
clock: make sync clock wait lockfree
Make the common case lockfree.
This commit is contained in:
parent
f4e57cee5d
commit
ba7157dce6
3 changed files with 111 additions and 84 deletions
|
@ -203,6 +203,8 @@ gst_clock_entry_new (GstClock * clock, GstClockTime time,
|
|||
entry->func = NULL;
|
||||
entry->user_data = NULL;
|
||||
entry->destroy_data = NULL;
|
||||
entry->unscheduled = FALSE;
|
||||
entry->woken_up = FALSE;
|
||||
|
||||
return (GstClockID) entry;
|
||||
}
|
||||
|
|
|
@ -260,6 +260,7 @@ typedef gboolean (*GstClockCallback) (GstClock *clock, GstClockTime time,
|
|||
* @GST_CLOCK_BADTIME: A bad time was provided to a function.
|
||||
* @GST_CLOCK_ERROR: An error occurred
|
||||
* @GST_CLOCK_UNSUPPORTED: Operation is not supported
|
||||
* @GST_CLOCK_DONE: The ClockID is done waiting
|
||||
*
|
||||
* The return value of a clock operation.
|
||||
*/
|
||||
|
@ -271,7 +272,8 @@ typedef enum
|
|||
GST_CLOCK_BUSY = 3,
|
||||
GST_CLOCK_BADTIME = 4,
|
||||
GST_CLOCK_ERROR = 5,
|
||||
GST_CLOCK_UNSUPPORTED = 6
|
||||
GST_CLOCK_UNSUPPORTED = 6,
|
||||
GST_CLOCK_DONE = 7
|
||||
} GstClockReturn;
|
||||
|
||||
/**
|
||||
|
@ -349,6 +351,8 @@ struct _GstClockEntry {
|
|||
GstClockCallback func;
|
||||
gpointer user_data;
|
||||
GDestroyNotify destroy_data;
|
||||
gboolean unscheduled;
|
||||
gboolean woken_up;
|
||||
};
|
||||
|
||||
/**
|
||||
|
|
|
@ -53,6 +53,11 @@
|
|||
# undef WIN32_LEAN_AND_MEAN
|
||||
#endif /* G_OS_WIN32 */
|
||||
|
||||
#define GET_ENTRY_STATUS(e) (g_atomic_int_get(&GST_CLOCK_ENTRY_STATUS(e)))
|
||||
#define SET_ENTRY_STATUS(e,val) (g_atomic_int_set(&GST_CLOCK_ENTRY_STATUS(e),(val)))
|
||||
#define CAS_ENTRY_STATUS(e,old,val) (g_atomic_int_compare_and_exchange(\
|
||||
((volatile gint *)&GST_CLOCK_ENTRY_STATUS(e)), (old), (val)))
|
||||
|
||||
/* Define this to get some extra debug about jitter from each clock_wait */
|
||||
#undef WAIT_DEBUGGING
|
||||
|
||||
|
@ -197,7 +202,7 @@ gst_system_clock_dispose (GObject * object)
|
|||
GstClockEntry *entry = (GstClockEntry *) entries->data;
|
||||
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK, "unscheduling entry %p", entry);
|
||||
entry->status = GST_CLOCK_UNSCHEDULED;
|
||||
SET_ENTRY_STATUS (entry, GST_CLOCK_UNSCHEDULED);
|
||||
}
|
||||
GST_CLOCK_BROADCAST (clock);
|
||||
gst_system_clock_add_wakeup (sysclock);
|
||||
|
@ -387,11 +392,7 @@ gst_system_clock_async_thread (GstClock * clock)
|
|||
|
||||
/* pick the next entry */
|
||||
entry = clock->entries->data;
|
||||
/* if it was unscheduled, just move on to the next entry */
|
||||
if (entry->status == GST_CLOCK_UNSCHEDULED) {
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK, "entry %p was unscheduled", entry);
|
||||
goto next_entry;
|
||||
}
|
||||
GST_OBJECT_UNLOCK (clock);
|
||||
|
||||
requested = entry->time;
|
||||
|
||||
|
@ -400,6 +401,8 @@ gst_system_clock_async_thread (GstClock * clock)
|
|||
gst_system_clock_id_wait_jitter_unlocked (clock, (GstClockID) entry,
|
||||
NULL, FALSE);
|
||||
|
||||
GST_OBJECT_LOCK (clock);
|
||||
|
||||
switch (res) {
|
||||
case GST_CLOCK_UNSCHEDULED:
|
||||
/* entry was unscheduled, move to the next */
|
||||
|
@ -442,7 +445,7 @@ gst_system_clock_async_thread (GstClock * clock)
|
|||
/* we set the entry back to the OK state. This is needed so that the
|
||||
* _unschedule() code can see if an entry is currently being waited
|
||||
* on (when its state is BUSY). */
|
||||
entry->status = GST_CLOCK_OK;
|
||||
SET_ENTRY_STATUS (entry, GST_CLOCK_OK);
|
||||
continue;
|
||||
default:
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK,
|
||||
|
@ -549,18 +552,16 @@ gst_system_clock_get_resolution (GstClock * clock)
|
|||
|
||||
/* synchronously wait on the given GstClockEntry.
|
||||
*
|
||||
* We do this by blocking on the global clock GCond variable with
|
||||
* the requested time as a timeout. This allows us to unblock the
|
||||
* entry by signaling the GCond variable.
|
||||
* We do this by blocking on the global GstPoll timer with
|
||||
* the requested timeout. This allows us to unblock the
|
||||
* entry by writing on the control fd.
|
||||
*
|
||||
* Note that signaling the global GCond unlocks all waiting entries. So
|
||||
* Note that writing the global GstPoll unlocks all waiting entries. So
|
||||
* we need to check if an unlocked entry has changed when it unlocks.
|
||||
*
|
||||
* Entries that arrive too late are simply not waited on and a
|
||||
* GST_CLOCK_EARLY result is returned.
|
||||
*
|
||||
* should be called with LOCK held.
|
||||
*
|
||||
* MT safe.
|
||||
*/
|
||||
static GstClockReturn
|
||||
|
@ -568,78 +569,95 @@ gst_system_clock_id_wait_jitter_unlocked (GstClock * clock,
|
|||
GstClockEntry * entry, GstClockTimeDiff * jitter, gboolean restart)
|
||||
{
|
||||
GstSystemClock *sysclock = GST_SYSTEM_CLOCK_CAST (clock);
|
||||
GstClockTime entryt, real, now;
|
||||
GstClockTime entryt, now;
|
||||
GstClockTimeDiff diff;
|
||||
GstClockReturn status;
|
||||
|
||||
if (G_UNLIKELY (GET_ENTRY_STATUS (entry) == GST_CLOCK_UNSCHEDULED))
|
||||
return GST_CLOCK_UNSCHEDULED;
|
||||
|
||||
/* need to call the overridden method because we want to sync against the time
|
||||
* of the clock, whatever the subclass uses as a clock. */
|
||||
real = GST_CLOCK_GET_CLASS (clock)->get_internal_time (clock);
|
||||
now = gst_clock_adjust_unlocked (clock, real);
|
||||
now = gst_clock_get_time (clock);
|
||||
|
||||
/* get the time of the entry */
|
||||
entryt = GST_CLOCK_ENTRY_TIME (entry);
|
||||
|
||||
if (jitter) {
|
||||
*jitter = GST_CLOCK_DIFF (entryt, now);
|
||||
}
|
||||
/* the diff of the entry with the clock is the amount of time we have to
|
||||
* wait */
|
||||
diff = entryt - now;
|
||||
diff = GST_CLOCK_DIFF (now, entryt);
|
||||
if (G_LIKELY (jitter))
|
||||
*jitter = -diff;
|
||||
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK, "entry %p"
|
||||
" time %" GST_TIME_FORMAT
|
||||
" now %" GST_TIME_FORMAT
|
||||
" real %" GST_TIME_FORMAT
|
||||
" diff (time-now) %" G_GINT64_FORMAT,
|
||||
entry,
|
||||
GST_TIME_ARGS (entryt), GST_TIME_ARGS (now), GST_TIME_ARGS (real), diff);
|
||||
entry, GST_TIME_ARGS (entryt), GST_TIME_ARGS (now), diff);
|
||||
|
||||
if (diff > 0) {
|
||||
if (G_LIKELY (diff > 0)) {
|
||||
#ifdef WAIT_DEBUGGING
|
||||
GstClockTime final;
|
||||
#endif
|
||||
|
||||
while (entry->status != GST_CLOCK_UNSCHEDULED) {
|
||||
while (TRUE) {
|
||||
gint pollret;
|
||||
|
||||
/* mark the entry as busy */
|
||||
entry->status = GST_CLOCK_BUSY;
|
||||
GST_OBJECT_UNLOCK (clock);
|
||||
do {
|
||||
status = GET_ENTRY_STATUS (entry);
|
||||
|
||||
/* now wait on the entry, it either times out or the fd is written. */
|
||||
/* stop when we are unscheduled */
|
||||
if (G_UNLIKELY (status == GST_CLOCK_UNSCHEDULED))
|
||||
goto done;
|
||||
|
||||
/* mark the entry as busy but watch out for intermediate unscheduled
|
||||
* statuses */
|
||||
} while (G_UNLIKELY (!CAS_ENTRY_STATUS (entry, status, GST_CLOCK_BUSY)));
|
||||
|
||||
/* now wait on the entry, it either times out or the fd is written. The
|
||||
* status of the entry is only BUSY around the poll. */
|
||||
pollret = gst_poll_wait (sysclock->priv->timer, diff);
|
||||
|
||||
/* another thread can read the fd before we get the lock */
|
||||
GST_OBJECT_LOCK (clock);
|
||||
if (entry->status == GST_CLOCK_UNSCHEDULED) {
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK, "entry %p unlocked", entry);
|
||||
gst_system_clock_remove_wakeup (sysclock);
|
||||
/* get the new status, mark as DONE. We do this so that the unschedule
|
||||
* function knows when we left the poll and doesn't need to wakeup the
|
||||
* poll anymore. */
|
||||
do {
|
||||
status = GET_ENTRY_STATUS (entry);
|
||||
/* we were unscheduled, exit immediately */
|
||||
if (G_UNLIKELY (status == GST_CLOCK_UNSCHEDULED))
|
||||
break;
|
||||
} while (G_UNLIKELY (!CAS_ENTRY_STATUS (entry, status, GST_CLOCK_DONE)));
|
||||
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK, "entry %p unlocked, status %d, ret %d",
|
||||
entry, status, pollret);
|
||||
|
||||
if (G_UNLIKELY (status == GST_CLOCK_UNSCHEDULED)) {
|
||||
/* try to clean up The unschedule function managed to set the status to
|
||||
* unscheduled. We now take the lock and mark the entry as unscheduled.
|
||||
* This makes sure that the unschedule function doesn't perform a
|
||||
* wakeup anymore. If the unschedule function has a change to perform
|
||||
* the wakeup before us, we clean up here */
|
||||
GST_OBJECT_LOCK (sysclock);
|
||||
entry->unscheduled = TRUE;
|
||||
if (entry->woken_up) {
|
||||
gst_system_clock_remove_wakeup (sysclock);
|
||||
}
|
||||
GST_OBJECT_UNLOCK (sysclock);
|
||||
goto done;
|
||||
} else {
|
||||
if (pollret != 0) {
|
||||
if (G_UNLIKELY (pollret != 0)) {
|
||||
/* some other id got unlocked */
|
||||
if (!restart) {
|
||||
/* this can happen if the entry got unlocked because of an async
|
||||
* entry was added to the head of the async queue. */
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK, "wakeup waiting for entry %p", entry);
|
||||
break;
|
||||
goto done;
|
||||
}
|
||||
|
||||
/* mark ourselves as EARLY, we release the lock and we could be
|
||||
* unscheduled ourselves but we don't want the unscheduling thread
|
||||
* to write on the control socket (it does that when an entry has a
|
||||
* BUSY status). */
|
||||
entry->status = GST_CLOCK_EARLY;
|
||||
|
||||
/* wait till all the entries got woken up */
|
||||
GST_OBJECT_LOCK (sysclock);
|
||||
gst_system_clock_wait_wakeup (sysclock);
|
||||
|
||||
/* we released the lock in the wait, recheck our status, we don't need
|
||||
* to remove the wakeup count because we marked the entry as EARLY
|
||||
* before releasing the object lock. */
|
||||
if (entry->status == GST_CLOCK_UNSCHEDULED) {
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK, "entry %p got unscheduled", entry);
|
||||
break;
|
||||
}
|
||||
GST_OBJECT_UNLOCK (sysclock);
|
||||
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK, "entry %p needs to be restarted",
|
||||
entry);
|
||||
|
@ -650,13 +668,13 @@ gst_system_clock_id_wait_jitter_unlocked (GstClock * clock,
|
|||
|
||||
/* reschedule if gst_poll_wait returned early or we have to reschedule after
|
||||
* an unlock*/
|
||||
real = GST_CLOCK_GET_CLASS (clock)->get_internal_time (clock);
|
||||
now = gst_clock_adjust_unlocked (clock, real);
|
||||
diff = entryt - now;
|
||||
now = gst_clock_get_time (clock);
|
||||
diff = GST_CLOCK_DIFF (now, entryt);
|
||||
|
||||
if (diff <= 0) {
|
||||
/* timeout, this is fine, we can report success now */
|
||||
entry->status = GST_CLOCK_OK;
|
||||
status = GST_CLOCK_OK;
|
||||
SET_ENTRY_STATUS (entry, status);
|
||||
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK,
|
||||
"entry %p finished, diff %" G_GINT64_FORMAT, entry, diff);
|
||||
|
@ -671,42 +689,31 @@ gst_system_clock_id_wait_jitter_unlocked (GstClock * clock,
|
|||
(final - target),
|
||||
((double) (GstClockTimeDiff) (final - target)) / GST_SECOND);
|
||||
#endif
|
||||
break;
|
||||
goto done;
|
||||
} else {
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK,
|
||||
"entry %p restart, diff %" G_GINT64_FORMAT, entry, diff);
|
||||
}
|
||||
}
|
||||
}
|
||||
} else if (diff == 0) {
|
||||
entry->status = GST_CLOCK_OK;
|
||||
} else {
|
||||
entry->status = GST_CLOCK_EARLY;
|
||||
/* we are right on time or too late */
|
||||
if (G_UNLIKELY (diff == 0))
|
||||
status = GST_CLOCK_OK;
|
||||
else
|
||||
status = GST_CLOCK_EARLY;
|
||||
|
||||
SET_ENTRY_STATUS (entry, status);
|
||||
}
|
||||
return entry->status;
|
||||
done:
|
||||
return status;
|
||||
}
|
||||
|
||||
static GstClockReturn
|
||||
gst_system_clock_id_wait_jitter (GstClock * clock, GstClockEntry * entry,
|
||||
GstClockTimeDiff * jitter)
|
||||
{
|
||||
GstClockReturn ret;
|
||||
|
||||
GST_OBJECT_LOCK (clock);
|
||||
if (G_UNLIKELY (entry->status == GST_CLOCK_UNSCHEDULED))
|
||||
goto was_unscheduled;
|
||||
|
||||
ret = gst_system_clock_id_wait_jitter_unlocked (clock, entry, jitter, TRUE);
|
||||
GST_OBJECT_UNLOCK (clock);
|
||||
|
||||
return ret;
|
||||
|
||||
/* ERRORS */
|
||||
was_unscheduled:
|
||||
{
|
||||
GST_OBJECT_UNLOCK (clock);
|
||||
return GST_CLOCK_UNSCHEDULED;
|
||||
}
|
||||
return gst_system_clock_id_wait_jitter_unlocked (clock, entry, jitter, TRUE);
|
||||
}
|
||||
|
||||
/* Start the async clock thread. Must be called with the object lock
|
||||
|
@ -760,7 +767,7 @@ gst_system_clock_id_wait_async (GstClock * clock, GstClockEntry * entry)
|
|||
if (G_UNLIKELY (!gst_system_clock_start_async (sysclock)))
|
||||
goto thread_error;
|
||||
|
||||
if (G_UNLIKELY (entry->status == GST_CLOCK_UNSCHEDULED))
|
||||
if (G_UNLIKELY (GET_ENTRY_STATUS (entry) == GST_CLOCK_UNSCHEDULED))
|
||||
goto was_unscheduled;
|
||||
|
||||
if (clock->entries)
|
||||
|
@ -778,14 +785,20 @@ gst_system_clock_id_wait_async (GstClock * clock, GstClockEntry * entry)
|
|||
* 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");
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK, "async entry added to head %p", head);
|
||||
if (head == NULL) {
|
||||
/* the list was empty before, signal the cond so that the async thread can
|
||||
* start taking a look at the queue */
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK, "first entry, sending signal");
|
||||
GST_CLOCK_BROADCAST (clock);
|
||||
} else {
|
||||
if (head->status == GST_CLOCK_BUSY) {
|
||||
GstClockReturn status;
|
||||
|
||||
status = GET_ENTRY_STATUS (head);
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK, "head entry %p status %d", head, status);
|
||||
|
||||
if (status == GST_CLOCK_BUSY) {
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK, "head entry is busy");
|
||||
/* the async thread was waiting for an entry, unlock the wait so that it
|
||||
* looks at the new head entry instead, we only need to do this once */
|
||||
if (!sysclock->priv->async_wakeup) {
|
||||
|
@ -825,21 +838,29 @@ static void
|
|||
gst_system_clock_id_unschedule (GstClock * clock, GstClockEntry * entry)
|
||||
{
|
||||
GstSystemClock *sysclock;
|
||||
GstClockReturn status;
|
||||
|
||||
sysclock = GST_SYSTEM_CLOCK_CAST (clock);
|
||||
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK, "unscheduling entry %p", entry);
|
||||
|
||||
GST_OBJECT_LOCK (clock);
|
||||
if (entry->status == GST_CLOCK_BUSY) {
|
||||
/* change the entry status to unscheduled */
|
||||
do {
|
||||
status = GET_ENTRY_STATUS (entry);
|
||||
} while (G_UNLIKELY (!CAS_ENTRY_STATUS (entry, status,
|
||||
GST_CLOCK_UNSCHEDULED)));
|
||||
|
||||
if (G_LIKELY (status == GST_CLOCK_BUSY)) {
|
||||
/* the entry was being busy, wake up all entries so that they recheck their
|
||||
* status. We cannot wake up just one entry because allocating such a
|
||||
* datastructure for each entry would be too heavy and unlocking an entry
|
||||
* is usually done when shutting down or some other exceptional case. */
|
||||
GST_CAT_DEBUG (GST_CAT_CLOCK, "entry was BUSY, doing wakeup");
|
||||
gst_system_clock_add_wakeup (sysclock);
|
||||
if (!entry->unscheduled && !entry->woken_up) {
|
||||
gst_system_clock_add_wakeup (sysclock);
|
||||
entry->woken_up = TRUE;
|
||||
}
|
||||
}
|
||||
/* when it leaves the poll, it'll detect the unscheduled */
|
||||
entry->status = GST_CLOCK_UNSCHEDULED;
|
||||
GST_OBJECT_UNLOCK (clock);
|
||||
}
|
||||
|
|
Loading…
Reference in a new issue