player_control: protect command, state, error with a mutex

Use GMutex/GCond instead of the notify library.  Manually lock the
player_control object before accessing the protected attributes.  Use
the GCond object to notify the player thread and the main thread.

12 files changed, 263 insertions, 89 deletions

diff --git a/src/decoder_api.c b/src/decoder_api.c
index 4cff9916..070151a6 100644
--- a/src/decoder_api.c
+++ b/src/decoder_api.c
@@ -61,7 +61,7 @@ void decoder_initialized(G_GNUC_UNUSED struct decoder * decoder,
 	dc.state = DECODE_STATE_DECODE;
 	decoder_unlock();
 
-	notify_signal(&pc.notify);
+	player_lock_signal();
 
 	g_debug("audio_format=%u:%u:%u, seekable=%s",
 		dc.in_audio_format.sample_rate, dc.in_audio_format.bits,
@@ -112,7 +112,7 @@ void decoder_command_finished(G_GNUC_UNUSED struct decoder * decoder)
 	dc.command = DECODE_COMMAND_NONE;
 	decoder_unlock();
 
-	notify_signal(&pc.notify);
+	player_lock_signal();
 }
 
 double decoder_seek_where(G_GNUC_UNUSED struct decoder * decoder)
@@ -184,7 +184,7 @@ do_send_tag(struct decoder *decoder, struct input_stream *is,
 		/* there is a partial chunk - flush it, we want the
 		   tag in a new chunk */
 		decoder_flush_chunk(decoder);
-		notify_signal(&pc.notify);
+		player_lock_signal();
 	}
 
 	assert(decoder->chunk == NULL);
@@ -297,7 +297,7 @@ decoder_data(struct decoder *decoder,
 		if (dest == NULL) {
 			/* the chunk is full, flush it */
 			decoder_flush_chunk(decoder);
-			notify_signal(&pc.notify);
+			player_lock_signal();
 			continue;
 		}
 
@@ -324,7 +324,7 @@ decoder_data(struct decoder *decoder,
 		if (full) {
 			/* the chunk is full, flush it */
 			decoder_flush_chunk(decoder);
-			notify_signal(&pc.notify);
+			player_lock_signal();
 		}
 
 		data += nbytes;
diff --git a/src/decoder_control.c b/src/decoder_control.c
index 3b993431..d7f5808f 100644
--- a/src/decoder_control.c
+++ b/src/decoder_control.c
@@ -18,7 +18,7 @@
  */
 
 #include "decoder_control.h"
-#include "notify.h"
+#include "player_control.h"
 
 #include <assert.h>
 
@@ -40,38 +40,34 @@ void dc_deinit(void)
 }
 
 static void
-dc_command_wait_locked(struct notify *notify)
+dc_command_wait_locked(void)
 {
 	while (dc.command != DECODE_COMMAND_NONE) {
 		decoder_signal();
-		decoder_unlock();
-
-		notify_wait(notify);
-
-		decoder_lock();
+		player_wait_decoder();
 	}
 }
 
 void
-dc_command_wait(struct notify *notify)
+dc_command_wait(void)
 {
 	decoder_lock();
-	dc_command_wait_locked(notify);
+	dc_command_wait_locked();
 	decoder_unlock();
 }
 
 static void
-dc_command_locked(struct notify *notify, enum decoder_command cmd)
+dc_command_locked(enum decoder_command cmd)
 {
 	dc.command = cmd;
-	dc_command_wait_locked(notify);
+	dc_command_wait_locked();
 }
 
 static void
-dc_command(struct notify *notify, enum decoder_command cmd)
+dc_command(enum decoder_command cmd)
 {
 	decoder_lock();
-	dc_command_locked(notify, cmd);
+	dc_command_locked(cmd);
 	decoder_unlock();
 }
 
@@ -86,13 +82,13 @@ static void dc_command_async(enum decoder_command cmd)
 }
 
 void
-dc_start(struct notify *notify, struct song *song)
+dc_start(struct song *song)
 {
 	assert(dc.pipe != NULL);
 	assert(song != NULL);
 
 	dc.next_song = song;
-	dc_command(notify, DECODE_COMMAND_START);
+	dc_command(DECODE_COMMAND_START);
 }
 
 void
@@ -106,7 +102,7 @@ dc_start_async(struct song *song)
 }
 
 void
-dc_stop(struct notify *notify)
+dc_stop(void)
 {
 	decoder_lock();
 
@@ -115,16 +111,16 @@ dc_stop(struct notify *notify)
 		   late and the decoder thread is already executing
 		   the old command, we'll call STOP again in this
 		   function (see below). */
-		dc_command_locked(notify, DECODE_COMMAND_STOP);
+		dc_command_locked(DECODE_COMMAND_STOP);
 
 	if (dc.state != DECODE_STATE_STOP && dc.state != DECODE_STATE_ERROR)
-		dc_command_locked(notify, DECODE_COMMAND_STOP);
+		dc_command_locked(DECODE_COMMAND_STOP);
 
 	decoder_unlock();
 }
 
 bool
-dc_seek(struct notify *notify, double where)
+dc_seek(double where)
 {
 	assert(dc.state != DECODE_STATE_START);
 	assert(where >= 0.0);
@@ -135,7 +131,7 @@ dc_seek(struct notify *notify, double where)
 
 	dc.seek_where = where;
 	dc.seek_error = false;
-	dc_command(notify, DECODE_COMMAND_SEEK);
+	dc_command(DECODE_COMMAND_SEEK);
 
 	if (dc.seek_error)
 		return false;
diff --git a/src/decoder_control.h b/src/decoder_control.h
index 7e861f97..6b65da2f 100644
--- a/src/decoder_control.h
+++ b/src/decoder_control.h
@@ -30,8 +30,6 @@
 #define DECODE_TYPE_FILE	0
 #define DECODE_TYPE_URL		1
 
-struct notify;
-
 enum decoder_state {
 	DECODE_STATE_STOP = 0,
 	DECODE_STATE_START,
@@ -205,19 +203,19 @@ decoder_current_song(void)
 }
 
 void
-dc_command_wait(struct notify *notify);
+dc_command_wait(void);
 
 void
-dc_start(struct notify *notify, struct song *song);
+dc_start(struct song *song);
 
 void
 dc_start_async(struct song *song);
 
 void
-dc_stop(struct notify *notify);
+dc_stop(void);
 
 bool
-dc_seek(struct notify *notify, double where);
+dc_seek(double where);
 
 void
 dc_quit(void);
diff --git a/src/decoder_internal.c b/src/decoder_internal.c
index 1b064d0a..db90333b 100644
--- a/src/decoder_internal.c
+++ b/src/decoder_internal.c
@@ -58,10 +58,7 @@ need_chunks(struct input_stream *is, bool do_wait)
 
 	if ((is == NULL || decoder_input_buffer(is) <= 0) && do_wait) {
 		decoder_wait();
-
-		decoder_unlock();
-		notify_signal(&pc.notify);
-		decoder_lock();
+		player_signal();
 
 		return dc.command;
 	}
diff --git a/src/decoder_thread.c b/src/decoder_thread.c
index 846b1235..712e4d20 100644
--- a/src/decoder_thread.c
+++ b/src/decoder_thread.c
@@ -112,9 +112,7 @@ static void decoder_run_song(const struct song *song, const char *uri)
 	dc.state = DECODE_STATE_START;
 	dc.command = DECODE_COMMAND_NONE;
 
-	decoder_unlock();
-	notify_signal(&pc.notify);
-	decoder_lock();
+	player_signal();
 
 	/* wait for the input stream to become ready; its metadata
 	   will be available then */
@@ -294,17 +292,13 @@ static gpointer decoder_task(G_GNUC_UNUSED gpointer arg)
 
 			dc.command = DECODE_COMMAND_NONE;
 
-			decoder_unlock();
-			notify_signal(&pc.notify);
-			decoder_lock();
+			player_signal();
 			break;
 
 		case DECODE_COMMAND_STOP:
 			dc.command = DECODE_COMMAND_NONE;
 
-			decoder_unlock();
-			notify_signal(&pc.notify);
-			decoder_lock();
+			player_signal();
 			break;
 
 		case DECODE_COMMAND_NONE:
diff --git a/src/main.c b/src/main.c
index 86fe069e..18647eb8 100644
--- a/src/main.c
+++ b/src/main.c
@@ -93,7 +93,7 @@ enum {
 GThread *main_task;
 GMainLoop *main_loop;
 
-struct notify main_notify;
+GCond *main_cond;
 
 static void
 glue_daemonize_init(const struct options *options)
@@ -321,7 +321,7 @@ int main(int argc, char *argv[])
 
 	main_task = g_thread_self();
 	main_loop = g_main_loop_new(NULL, FALSE);
-	notify_init(&main_notify);
+	main_cond = g_cond_new();
 
 	event_pipe_init();
 	event_pipe_register(PIPE_EVENT_IDLE, idle_event_emitted);
@@ -415,7 +415,7 @@ int main(int argc, char *argv[])
 	sticker_global_finish();
 #endif
 
-	notify_deinit(&main_notify);
+	g_cond_free(main_cond);
 	event_pipe_deinit();
 
 	playlist_list_global_finish();
diff --git a/src/main.h b/src/main.h
index 8ed02bf5..de673829 100644
--- a/src/main.h
+++ b/src/main.h
@@ -26,6 +26,6 @@ extern GThread *main_task;
 
 extern GMainLoop *main_loop;
 
-extern struct notify main_notify;
+extern GCond *main_cond;
 
 #endif
diff --git a/src/output_all.c b/src/output_all.c
index 08f4ee0d..bdf0385b 100644
--- a/src/output_all.c
+++ b/src/output_all.c
@@ -445,10 +445,15 @@ audio_output_all_check(void)
 bool
 audio_output_all_wait(unsigned threshold)
 {
-	if (audio_output_all_check() < threshold)
+	player_lock();
+
+	if (audio_output_all_check() < threshold) {
+		player_unlock();
 		return true;
+	}
 
-	notify_wait(&pc.notify);
+	player_wait();
+	player_unlock();
 
 	return audio_output_all_check() < threshold;
 }
diff --git a/src/output_thread.c b/src/output_thread.c
index 24a22f6d..ef8fe741 100644
--- a/src/output_thread.c
+++ b/src/output_thread.c
@@ -359,7 +359,7 @@ ao_play(struct audio_output *ao)
 	ao->chunk_finished = true;
 
 	g_mutex_unlock(ao->mutex);
-	notify_signal(&pc.notify);
+	player_lock_signal();
 	g_mutex_lock(ao->mutex);
 
 	return true;
diff --git a/src/player_control.c b/src/player_control.c
index 23ae136a..aa018ced 100644
--- a/src/player_control.c
+++ b/src/player_control.c
@@ -18,6 +18,7 @@
  */
 
 #include "player_control.h"
+#include "decoder_control.h"
 #include "path.h"
 #include "log.h"
 #include "tag.h"
@@ -35,7 +36,10 @@ void pc_init(unsigned buffer_chunks, unsigned int buffered_before_play)
 {
 	pc.buffer_chunks = buffer_chunks;
 	pc.buffered_before_play = buffered_before_play;
-	notify_init(&pc.notify);
+
+	pc.mutex = g_mutex_new();
+	pc.cond = g_cond_new();
+
 	pc.command = PLAYER_COMMAND_NONE;
 	pc.error = PLAYER_ERROR_NOERROR;
 	pc.state = PLAYER_STATE_STOP;
@@ -44,7 +48,16 @@ void pc_init(unsigned buffer_chunks, unsigned int buffered_before_play)
 
 void pc_deinit(void)
 {
-	notify_deinit(&pc.notify);
+	g_cond_free(pc.cond);
+	g_mutex_free(pc.mutex);
+}
+
+void
+player_wait_decoder(void)
+{
+	/* during this function, the decoder lock is held, because
+	   we're waiting for the decoder thread */
+	g_cond_wait(pc.cond, dc.mutex);
 }
 
 void
@@ -56,15 +69,30 @@ pc_song_deleted(const struct song *song)
 	}
 }
 
-static void player_command(enum player_command cmd)
+static void
+player_command_wait_locked(void)
+{
+	while (pc.command != PLAYER_COMMAND_NONE) {
+		player_signal();
+		g_cond_wait(main_cond, pc.mutex);
+	}
+}
+
+static void
+player_command_locked(enum player_command cmd)
 {
 	assert(pc.command == PLAYER_COMMAND_NONE);
 
 	pc.command = cmd;
-	while (pc.command != PLAYER_COMMAND_NONE) {
-		notify_signal(&pc.notify);
-		notify_wait(&main_notify);
-	}
+	player_command_wait_locked();
+}
+
+static void
+player_command(enum player_command cmd)
+{
+	player_lock();
+	player_command_locked(cmd);
+	player_unlock();
 }
 
 void
diff --git a/src/player_control.h b/src/player_control.h
index c0f1d4f0..449e98aa 100644
--- a/src/player_control.h
+++ b/src/player_control.h
@@ -88,10 +88,19 @@ struct player_control {
 	    thread isn't running */
 	GThread *thread;
 
-	struct notify notify;
-	volatile enum player_command command;
-	volatile enum player_state state;
-	volatile enum player_error error;
+	/**
+	 * This lock protects #command, #state, #error.
+	 */
+	GMutex *mutex;
+
+	/**
+	 * Trigger this object after you have modified #command.
+	 */
+	GCond *cond;
+
+	enum player_command command;
+	enum player_state state;
+	enum player_error error;
 	uint16_t bit_rate;
 	struct audio_format audio_format;
 	float total_time;
@@ -110,6 +119,67 @@ void pc_init(unsigned buffer_chunks, unsigned buffered_before_play);
 void pc_deinit(void);
 
 /**
+ * Locks the #player_control object.
+ */
+static inline void
+player_lock(void)
+{
+	g_mutex_lock(pc.mutex);
+}
+
+/**
+ * Unlocks the #player_control object.
+ */
+static inline void
+player_unlock(void)
+{
+	g_mutex_unlock(pc.mutex);
+}
+
+/**
+ * Waits for a signal on the #player_control object.  This function is
+ * only valid in the player thread.  The object must be locked prior
+ * to calling this function.
+ */
+static inline void
+player_wait(void)
+{
+	g_cond_wait(pc.cond, pc.mutex);
+}
+
+/**
+ * Waits for a signal on the #player_control object.  This function is
+ * only valid in the player thread.  The #decoder_control object must
+ * be locked prior to calling this function.
+ *
+ * Note the small difference to the player_wait() function!
+ */
+void
+player_wait_decoder(void);
+
+/**
+ * Signals the #player_control object.  The object should be locked
+ * prior to calling this function.
+ */
+static inline void
+player_signal(void)
+{
+	g_cond_signal(pc.cond);
+}
+
+/**
+ * Signals the #player_control object.  The object is temporarily
+ * locked by this function.
+ */
+static inline void
+player_lock_signal(void)
+{
+	player_lock();
+	player_signal();
+	player_unlock();
+}
+
+/**
  * Call this function when the specified song pointer is about to be
  * invalidated.  This makes sure that player_control.errored_song does
  * not point to an invalid pointer.
diff --git a/src/player_thread.c b/src/player_thread.c
index dbafa168..0c88d1a5 100644
--- a/src/player_thread.c
+++ b/src/player_thread.c
@@ -106,21 +106,30 @@ struct player {
 
 static struct music_buffer *player_buffer;
 
-static void player_command_finished(void)
+static void player_command_finished_locked(void)
 {
 	assert(pc.command != PLAYER_COMMAND_NONE);
 
 	pc.command = PLAYER_COMMAND_NONE;
-	notify_signal(&main_notify);
+	g_cond_signal(main_cond);
+}
+
+static void player_command_finished(void)
+{
+	player_lock();
+	player_command_finished_locked();
+	player_unlock();
 }
 
 /**
  * Stop the decoder and clears (and frees) its music pipe.
+ *
+ * Player lock is not held.
  */
 static void
 player_dc_stop(struct player *player)
 {
-	dc_stop(&pc.notify);
+	dc_stop();
 
 	if (dc.pipe != NULL) {
 		/* clear and free the decoder pipe */
@@ -138,17 +147,23 @@ player_dc_stop(struct player *player)
  * After the decoder has been started asynchronously, wait for the
  * "START" command to finish.  The decoder may not be initialized yet,
  * i.e. there is no audio_format information yet.
+ *
+ * The player lock is not held.
  */
 static bool
 player_wait_for_decoder(struct player *player)
 {
-	dc_command_wait(&pc.notify);
+	dc_command_wait();
 
 	if (decoder_lock_has_failed()) {
 		assert(dc.next_song == NULL || dc.next_song->uri != NULL);
+
+		player_lock();
 		pc.errored_song = dc.next_song;
 		pc.error = PLAYER_ERROR_FILE;
 		pc.next_song = NULL;
+		player_unlock();
+
 		player->queued = false;
 		return false;
 	}
@@ -177,6 +192,8 @@ player_wait_for_decoder(struct player *player)
  * The decoder has acknowledged the "START" command (see
  * player_wait_for_decoder()).  This function checks if the decoder
  * initialization has completed yet.
+ *
+ * The player lock is not held.
  */
 static bool
 player_check_decoder_startup(struct player *player)
@@ -234,8 +251,8 @@ player_check_decoder_startup(struct player *player)
 	} else {
 		/* the decoder is not yet ready; wait
 		   some more */
+		player_wait_decoder();
 		decoder_unlock();
-		notify_wait(&pc.notify);
 
 		return true;
 	}
@@ -245,6 +262,8 @@ player_check_decoder_startup(struct player *player)
  * Sends a chunk of silence to the audio outputs.  This is called when
  * there is not enough decoded data in the pipe yet, to prevent
  * underruns in the hardware buffers.
+ *
+ * The player lock is not held.
  */
 static bool
 player_send_silence(struct player *player)
@@ -281,6 +300,8 @@ player_send_silence(struct player *player)
 
 /**
  * This is the handler for the #PLAYER_COMMAND_SEEK command.
+ *
+ * The player lock is not held.
  */
 static bool player_seek_decoder(struct player *player)
 {
@@ -332,7 +353,7 @@ static bool player_seek_decoder(struct player *player)
 	if (where < 0.0)
 		where = 0.0;
 
-	ret = dc_seek(&pc.notify, where);
+	ret = dc_seek(where);
 	if (!ret) {
 		/* decoder failure */
 		player_command_finished();
@@ -353,6 +374,9 @@ static bool player_seek_decoder(struct player *player)
 	return true;
 }
 
+/**
+ * Player lock must be held before calling.
+ */
 static void player_process_command(struct player *player)
 {
 	switch (pc.command) {
@@ -363,8 +387,10 @@ static void player_process_command(struct player *player)
 		break;
 
 	case PLAYER_COMMAND_UPDATE_AUDIO:
+		player_unlock();
 		audio_output_all_enable_disable();
-		player_command_finished();
+		player_lock();
+		player_command_finished_locked();
 		break;
 
 	case PLAYER_COMMAND_QUEUE:
@@ -373,21 +399,28 @@ static void player_process_command(struct player *player)
 		assert(dc.pipe == NULL || dc.pipe == player->pipe);
 
 		player->queued = true;
-		player_command_finished();
+		player_command_finished_locked();
 		break;
 
 	case PLAYER_COMMAND_PAUSE:
+		player_unlock();
+
 		player->paused = !player->paused;
 		if (player->paused) {
 			audio_output_all_pause();
+			player_lock();
+
 			pc.state = PLAYER_STATE_PAUSE;
 		} else if (!audio_format_defined(&player->play_audio_format)) {
 			/* the decoder hasn't provided an audio format
 			   yet - don't open the audio device yet */
+			player_lock();
 
 			pc.state = PLAYER_STATE_PLAY;
 		} else if (audio_output_all_open(&player->play_audio_format, player_buffer)) {
 			/* unpaused, continue playing */
+			player_lock();
+
 			pc.state = PLAYER_STATE_PLAY;
 		} else {
 			/* the audio device has failed - rollback to
@@ -397,13 +430,17 @@ static void player_process_command(struct player *player)
 			pc.error = PLAYER_ERROR_AUDIO;
 
 			player->paused = true;
+
+			player_lock();
 		}
 
-		player_command_finished();
+		player_command_finished_locked();
 		break;
 
 	case PLAYER_COMMAND_SEEK:
+		player_unlock();
 		player_seek_decoder(player);
+		player_lock();
 		break;
 
 	case PLAYER_COMMAND_CANCEL:
@@ -415,26 +452,32 @@ static void player_process_command(struct player *player)
 			return;
 		}
 
-		if (dc.pipe != NULL && dc.pipe != player->pipe)
+		if (dc.pipe != NULL && dc.pipe != player->pipe) {
 			/* the decoder is already decoding the song -
 			   stop it and reset the position */
+			player_unlock();
 			player_dc_stop(player);
+			player_lock();
+		}
 
 		pc.next_song = NULL;
 		player->queued = false;
-		player_command_finished();
+		player_command_finished_locked();
 		break;
 
 	case PLAYER_COMMAND_REFRESH:
 		if (audio_format_defined(&player->play_audio_format) &&
-		    !player->paused)
+		    !player->paused) {
+			player_unlock();
 			audio_output_all_check();
+			player_lock();
+		}
 
 		pc.elapsed_time = audio_output_all_get_elapsed_time();
 		if (pc.elapsed_time < 0.0)
 			pc.elapsed_time = player->elapsed_time;
 
-		player_command_finished();
+		player_command_finished_locked();
 		break;
 	}
 }
@@ -468,6 +511,8 @@ update_song_tag(struct song *song, const struct tag *new_tag)
  * Plays a #music_chunk object (after applying software volume).  If
  * it contains a (stream) tag, copy it to the current song, so MPD's
  * playlist reflects the new stream tag.
+ *
+ * Player lock is not held.
  */
 static bool
 play_chunk(struct song *song, struct music_chunk *chunk,
@@ -553,10 +598,9 @@ play_next_chunk(struct player *player)
 			} else {
 				/* wait for the decoder */
 				decoder_signal();
+				player_wait_decoder();
 				decoder_unlock();
 
-				notify_wait(&pc.notify);
-
 				return true;
 			}
 		}
@@ -574,6 +618,8 @@ play_next_chunk(struct player *player)
 	if (!success) {
 		music_buffer_return(player_buffer, chunk);
 
+		player_lock();
+
 		pc.error = PLAYER_ERROR_AUDIO;
 
 		/* pause: the user may resume playback as soon as an
@@ -581,6 +627,8 @@ play_next_chunk(struct player *player)
 		pc.state = PLAYER_STATE_PAUSE;
 		player->paused = true;
 
+		player_unlock();
+
 		return false;
 	}
 
@@ -602,6 +650,8 @@ play_next_chunk(struct player *player)
  * has consumed all chunks of the current song, and we should start
  * sending chunks from the next one.
  *
+ * The player lock is not held.
+ *
  * @return true on success, false on error (playback will be stopped)
  */
 static bool
@@ -643,31 +693,38 @@ static void do_play(void)
 		.elapsed_time = 0.0,
 	};
 
+	player_unlock();
+
 	player.pipe = music_pipe_new();
 
 	dc.buffer = player_buffer;
 	dc.pipe = player.pipe;
-	dc_start(&pc.notify, pc.next_song);
+	dc_start(pc.next_song);
 	if (!player_wait_for_decoder(&player)) {
 		player_dc_stop(&player);
 		player_command_finished();
 		music_pipe_free(player.pipe);
 		event_pipe_emit(PIPE_EVENT_PLAYLIST);
+		player_lock();
 		return;
 	}
 
+	player_lock();
 	pc.state = PLAYER_STATE_PLAY;
-	player_command_finished();
+	player_command_finished_locked();
 
 	while (true) {
 		player_process_command(&player);
 		if (pc.command == PLAYER_COMMAND_STOP ||
 		    pc.command == PLAYER_COMMAND_EXIT ||
 		    pc.command == PLAYER_COMMAND_CLOSE_AUDIO) {
+			player_unlock();
 			audio_output_all_cancel();
 			break;
 		}
 
+		player_unlock();
+
 		if (player.buffering) {
 			/* buffering at the start of the song - wait
 			   until the buffer is large enough, to
@@ -683,7 +740,10 @@ static void do_play(void)
 				    !player_send_silence(&player))
 					break;
 
-				notify_wait(&pc.notify);
+				decoder_lock();
+				/* XXX race condition: check decoder again */
+				player_wait_decoder();
+				decoder_unlock();
 				continue;
 			} else {
 				/* buffering is complete */
@@ -698,6 +758,8 @@ static void do_play(void)
 			success = player_check_decoder_startup(&player);
 			if (!success)
 				break;
+
+			player_lock();
 			continue;
 		}
 
@@ -741,9 +803,11 @@ static void do_play(void)
 				player.xfade = XFADE_DISABLED;
 		}
 
-		if (player.paused)
-			notify_wait(&pc.notify);
-		else if (music_pipe_size(player.pipe) > 0) {
+		if (player.paused) {
+			player_lock();
+			player_wait();
+			continue;
+		} else if (music_pipe_size(player.pipe) > 0) {
 			/* at least one music chunk is ready - send it
 			   to the audio output */
 
@@ -773,6 +837,8 @@ static void do_play(void)
 			if (!player_send_silence(&player))
 				break;
 		}
+
+		player_lock();
 	}
 
 	player_dc_stop(&player);
@@ -783,8 +849,13 @@ static void do_play(void)
 	music_pipe_clear(player.pipe, player_buffer);
 	music_pipe_free(player.pipe);
 
+	player_lock();
 	pc.state = PLAYER_STATE_STOP;
+	player_unlock();
+
 	event_pipe_emit(PIPE_EVENT_PLAYLIST);
+
+	player_lock();
 }
 
 static gpointer player_task(G_GNUC_UNUSED gpointer arg)
@@ -793,6 +864,8 @@ static gpointer player_task(G_GNUC_UNUSED gpointer arg)
 
 	player_buffer = music_buffer_new(pc.buffer_chunks);
 
+	player_lock();
+
 	while (1) {
 		switch (pc.command) {
 		case PLAYER_COMMAND_QUEUE:
@@ -802,18 +875,25 @@ static gpointer player_task(G_GNUC_UNUSED gpointer arg)
 			break;
 
 		case PLAYER_COMMAND_STOP:
+			player_unlock();
 			audio_output_all_cancel();
+			player_lock();
+
 			/* fall through */
 
 		case PLAYER_COMMAND_SEEK:
 		case PLAYER_COMMAND_PAUSE:
 			pc.next_song = NULL;
-			player_command_finished();
+			player_command_finished_locked();
 			break;
 
 		case PLAYER_COMMAND_CLOSE_AUDIO:
+			player_unlock();
+
 			audio_output_all_close();
-			player_command_finished();
+
+			player_lock();
+			player_command_finished_locked();
 
 #ifndef NDEBUG
 			/* in the DEBUG build, check for leaked
@@ -826,33 +906,39 @@ static gpointer player_task(G_GNUC_UNUSED gpointer arg)
 			break;
 
 		case PLAYER_COMMAND_UPDATE_AUDIO:
+			player_unlock();
 			audio_output_all_enable_disable();
-			player_command_finished();
+			player_lock();
+			player_command_finished_locked();
 			break;
 
 		case PLAYER_COMMAND_EXIT:
+			player_unlock();
+
 			dc_quit();
 			audio_output_all_close();
 			music_buffer_free(player_buffer);
+
 			player_command_finished();
 			g_thread_exit(NULL);
 			break;
 
 		case PLAYER_COMMAND_CANCEL:
 			pc.next_song = NULL;
-			player_command_finished();
+			player_command_finished_locked();
 			break;
 
 		case PLAYER_COMMAND_REFRESH:
 			/* no-op when not playing */
-			player_command_finished();
+			player_command_finished_locked();
 			break;
 
 		case PLAYER_COMMAND_NONE:
-			notify_wait(&pc.notify);
+			player_wait();
 			break;
 		}
 	}
+
 	return NULL;
 }