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https://gitlab.freedesktop.org/gstreamer/gstreamer.git
synced 2024-12-24 17:20:36 +00:00
poll: make timer polls lockfree
Make sure we don't take a mutex in the normal code path of the timer poll.
This commit is contained in:
Wim Taymans
parent
e0f15e666a
commit
73ee14302f
1 changed files with 64 additions and 33 deletions
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@ -147,9 +147,13 @@ struct _GstPoll
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GstPollMode mode;
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GMutex *lock;
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/* array of fds, always written to and read from with lock */
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GArray *fds;
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/* array of active fds, only written to from the waiting thread with the
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* lock and read from with the lock or without the lock from the waiting
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* thread */
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GArray *active_fds;
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#ifndef G_OS_WIN32
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GstPollFD control_read_fd;
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GstPollFD control_write_fd;
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@ -163,12 +167,23 @@ struct _GstPoll
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gboolean controllable;
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gboolean new_controllable;
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guint waiting;
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guint control_pending;
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gboolean flushing;
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volatile gint waiting;
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volatile gint control_pending;
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volatile gint flushing;
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gboolean timer;
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volatile gint rebuild;
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};
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#define IS_FLUSHING(s) (g_atomic_int_get(&(s)->flushing))
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#define SET_FLUSHING(s,val) (g_atomic_int_set(&(s)->flushing, (val)))
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#define INC_WAITING(s) (g_atomic_int_exchange_and_add(&(s)->waiting, 1))
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#define DEC_WAITING(s) (g_atomic_int_exchange_and_add(&(s)->waiting, -1))
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#define GET_WAITING(s) (g_atomic_int_get(&(s)->waiting))
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#define TEST_REBUILD(s) (g_atomic_int_compare_and_exchange(&(s)->rebuild, 1, 0))
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#define MARK_REBUILD(s) (g_atomic_int_set(&(s)->rebuild, 1))
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static gint
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find_index (GArray * array, GstPollFD * fd)
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{
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@ -217,14 +232,22 @@ selectable_fds (const GstPoll * set)
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{
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guint i;
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g_mutex_lock (set->lock);
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for (i = 0; i < set->fds->len; i++) {
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struct pollfd *pfd = &g_array_index (set->fds, struct pollfd, i);
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if (pfd->fd >= FD_SETSIZE)
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return FALSE;
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goto too_many;
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}
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g_mutex_unlock (set->lock);
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return TRUE;
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too_many:
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{
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g_mutex_unlock (set->lock);
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return FALSE;
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}
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}
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/* check if the timeout will convert to a timeout value used for poll()
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@ -643,6 +666,7 @@ gst_poll_add_fd_unlocked (GstPoll * set, GstPollFD * fd)
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fd->idx = set->fds->len - 1;
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#endif
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MARK_REBUILD (set);
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} else {
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GST_WARNING ("%p: couldn't find fd !", set);
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}
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@ -718,6 +742,7 @@ gst_poll_remove_fd (GstPoll * set, GstPollFD * fd)
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/* mark fd as removed by setting the index to -1 */
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fd->idx = -1;
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MARK_REBUILD (set);
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} else {
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GST_WARNING ("%p: couldn't find fd !", set);
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}
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@ -769,6 +794,7 @@ gst_poll_fd_ctl_write (GstPoll * set, GstPollFD * fd, gboolean active)
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gst_poll_update_winsock_event_mask (set, idx, FD_WRITE | FD_CONNECT,
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active);
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#endif
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MARK_REBUILD (set);
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} else {
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GST_WARNING ("%p: couldn't find fd !", set);
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}
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@ -799,6 +825,7 @@ gst_poll_fd_ctl_read_unlocked (GstPoll * set, GstPollFD * fd, gboolean active)
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#else
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gst_poll_update_winsock_event_mask (set, idx, FD_READ | FD_ACCEPT, active);
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#endif
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MARK_REBUILD (set);
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} else {
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GST_WARNING ("%p: couldn't find fd !", set);
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}
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@ -870,6 +897,7 @@ gst_poll_fd_ignored (GstPoll * set, GstPollFD * fd)
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WinsockFd *wfd = &g_array_index (set->fds, WinsockFd, idx);
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wfd->ignored_event_mask = wfd->event_mask & (FD_READ | FD_WRITE);
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MARK_REBUILD (set);
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}
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g_mutex_unlock (set->lock);
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@ -1132,25 +1160,27 @@ gint
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gst_poll_wait (GstPoll * set, GstClockTime timeout)
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{
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gboolean restarting;
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gboolean is_timer;
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int res;
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gint old_waiting;
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g_return_val_if_fail (set != NULL, -1);
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g_mutex_lock (set->lock);
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GST_DEBUG ("timeout :%" GST_TIME_FORMAT, GST_TIME_ARGS (timeout));
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is_timer = set->timer;
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/* add one more waiter */
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old_waiting = INC_WAITING (set);
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/* we cannot wait from multiple threads unless we are a timer */
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if (G_UNLIKELY (set->waiting > 0 && !set->timer))
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if (G_UNLIKELY (old_waiting > 0 && !is_timer))
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goto already_waiting;
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/* flushing, exit immediatly */
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if (G_UNLIKELY (set->flushing))
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if (G_UNLIKELY (IS_FLUSHING (set)))
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goto flushing;
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/* add one more waiter */
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set->waiting++;
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do {
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GstPollMode mode;
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@ -1159,6 +1189,8 @@ gst_poll_wait (GstPoll * set, GstClockTime timeout)
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mode = choose_mode (set, timeout);
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if (TEST_REBUILD (set)) {
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g_mutex_lock (set->lock);
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#ifndef G_OS_WIN32
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g_array_set_size (set->active_fds, set->fds->len);
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memcpy (set->active_fds->data, set->fds->data,
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@ -1167,8 +1199,8 @@ gst_poll_wait (GstPoll * set, GstClockTime timeout)
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if (!gst_poll_prepare_winsock_active_sets (set))
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goto winsock_error;
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#endif
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g_mutex_unlock (set->lock);
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}
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switch (mode) {
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case GST_POLL_MODE_AUTO:
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@ -1316,15 +1348,16 @@ gst_poll_wait (GstPoll * set, GstClockTime timeout)
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}
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}
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if (!is_timer) {
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g_mutex_lock (set->lock);
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if (!set->timer)
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gst_poll_check_ctrl_commands (set, res, &restarting);
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g_mutex_unlock (set->lock);
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}
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/* update the controllable state if needed */
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set->controllable = set->new_controllable;
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if (G_UNLIKELY (set->flushing)) {
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if (G_UNLIKELY (IS_FLUSHING (set))) {
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/* we got woken up and we are flushing, we need to stop */
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errno = EBUSY;
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res = -1;
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@ -1332,30 +1365,28 @@ gst_poll_wait (GstPoll * set, GstClockTime timeout)
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}
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} while (G_UNLIKELY (restarting));
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set->waiting--;
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g_mutex_unlock (set->lock);
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DEC_WAITING (set);
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return res;
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/* ERRORS */
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already_waiting:
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{
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g_mutex_unlock (set->lock);
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DEC_WAITING (set);
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errno = EPERM;
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return -1;
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}
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flushing:
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{
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g_mutex_unlock (set->lock);
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DEC_WAITING (set);
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errno = EBUSY;
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return -1;
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}
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#ifdef G_OS_WIN32
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winsock_error:
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{
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set->waiting--;
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g_mutex_unlock (set->lock);
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DEC_WAITING (set);
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return -1;
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}
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#endif
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@ -1405,7 +1436,7 @@ gst_poll_set_controllable (GstPoll * set, gboolean controllable)
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/* delay the change of the controllable state if we are waiting */
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set->new_controllable = controllable;
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if (set->waiting == 0)
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if (GET_WAITING (set) == 0)
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set->controllable = controllable;
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g_mutex_unlock (set->lock);
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@ -1441,7 +1472,7 @@ gst_poll_restart (GstPoll * set)
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g_mutex_lock (set->lock);
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if (set->controllable && set->waiting > 0) {
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if (set->controllable && GET_WAITING (set) > 0) {
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#ifndef G_OS_WIN32
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gint result;
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@ -1476,9 +1507,9 @@ gst_poll_set_flushing (GstPoll * set, gboolean flushing)
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g_mutex_lock (set->lock);
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/* update the new state first */
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set->flushing = flushing;
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SET_FLUSHING (set, flushing);
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if (flushing && set->controllable && set->waiting > 0) {
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if (flushing && set->controllable && GET_WAITING (set) > 0) {
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/* we are flushing, controllable and waiting, wake up the waiter. When we
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* stop the flushing operation we don't clear the wakeup fd here, this will
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* happen in the _wait() thread. */
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