From: Andre Noll <maan@systemlinux.org>
Date: Sun, 25 Nov 2012 13:00:08 +0000 (+0100)
Subject: Merge branch 't/osx_writer_improvements'
X-Git-Tag: v0.4.12~8
X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=commitdiff_plain;h=107d4619b3a6a8bdc1a85c8021cb1951244e7626;hp=00583bed658c70aacf2a94532904fd403c5ee7f1

Merge branch 't/osx_writer_improvements'

Cooking since 2012-10-30.

	9eaa22 osx_write: Check return value of AudioOutputUnitStart().
	831db3 osx_write: Be careful when dereferencing the private_data pointer.
	97902a osx: Treat writer node as an internal buffer tree node.
	1c6fa9 osx_write: Add big fat comment on callback btr node.
---

diff --git a/NEWS b/NEWS
index 2c05b8f9..69372cc4 100644
--- a/NEWS
+++ b/NEWS
@@ -8,6 +8,7 @@
 	- Overhaul of the build system: All generated files are now
 	  written to the "build" directory.
 	- The modular mixer API and the alsa mixer.
+	- Minor fixes for the osx writer.
 
 --------------------------------------
 0.4.11 (2012-07-20) "mutual diversity"
diff --git a/osx_write.c b/osx_write.c
index 8dcfb4cd..2894f11e 100644
--- a/osx_write.c
+++ b/osx_write.c
@@ -43,9 +43,28 @@ struct private_osx_write_data {
 	unsigned sample_format;
 	/** Number of channels of the current audio stream. */
 	unsigned channels;
-	/** Serializes access to buffer tree nodes. */
+	/**
+	 * Serializes access to buffer tree nodes between the writer and
+	 * the callback which runs in a different thread.
+	 */
 	int mutex;
-	/** The btr node of the callback. */
+	/**
+	 * The btr node of the callback.
+	 *
+	 * Although access to the btr node is serialized between the writer and
+	 * the callback via the above mutex, this does not stop other buffer
+	 * tree nodes, for example the decoder, to race against the osx
+	 * callback.
+	 *
+	 * However, since all operations on buffer tree nodes are local in the
+	 * sense that they only affect one level in the buffer tree (i.e.
+	 * parent or child nodes, but not the grandparent or the
+	 * grandchildren), we may work around this problem by using another
+	 * buffer tree node for the callback.
+	 *
+	 * The writer grabs the mutex in its post_select method and pushes down
+	 * the buffers to the callback node.
+	 */
 	struct btr_node *callback_btrn;
 };
 
@@ -59,10 +78,14 @@ static OSStatus osx_callback(void *cb_arg, __a_unused AudioUnitRenderActionFlags
 {
 	int i;
 	struct writer_node *wn = cb_arg;
-	struct private_osx_write_data *powd = wn->private_data;
+	struct private_osx_write_data *powd;
 	size_t samples_have, samples_want = 0;
 
+	powd = wn->private_data;
 	mutex_lock(powd->mutex);
+	powd = wn->private_data;
+	if (!powd || !wn->btrn)
+		goto out;
 	/*
 	 * We fill with zeros if no data was yet written and we do not have
 	 * enough to fill all buffers.
@@ -266,7 +289,7 @@ static void osx_write_pre_select(struct sched *s, struct task *t)
 	}
 
 	mutex_lock(powd->mutex);
-	ret = btr_node_status(wn->btrn, wn->min_iqs, BTR_NT_LEAF);
+	ret = btr_node_status(wn->btrn, wn->min_iqs, BTR_NT_INTERNAL);
 	if (ret < 0)
 		drain_delay_nec = need_drain_delay(powd);
 	mutex_unlock(powd->mutex);
@@ -295,25 +318,32 @@ static void osx_write_post_select(__a_unused struct sched *s, struct task *t)
 		if (ret < 0)
 			goto remove_btrn;
 		powd = wn->private_data;
-		AudioOutputUnitStart(powd->audio_unit);
+		ret = -E_UNIT_START;
+		if (AudioOutputUnitStart(powd->audio_unit) != noErr) {
+			AudioUnitUninitialize(powd->audio_unit);
+			CloseComponent(powd->audio_unit);
+			btr_remove_node(&powd->callback_btrn);
+			goto remove_btrn;
+		}
 	}
 	mutex_lock(powd->mutex);
-	btr_pushdown(btrn);
-	ret = btr_node_status(btrn, wn->min_iqs, BTR_NT_LEAF);
+	ret = btr_node_status(btrn, wn->min_iqs, BTR_NT_INTERNAL);
+	if (ret > 0)
+		btr_pushdown(btrn);
 	if (ret < 0 && need_drain_delay(powd))
 		ret = 0;
-	mutex_unlock(powd->mutex);
-
-	if (ret >= 0)
-		goto out;
+	if (ret >= 0) {
+		mutex_unlock(powd->mutex);
+		return;
+	}
 	AudioOutputUnitStop(powd->audio_unit);
 	AudioUnitUninitialize(powd->audio_unit);
 	CloseComponent(powd->audio_unit);
 	btr_remove_node(&powd->callback_btrn);
+	mutex_unlock(powd->mutex);
 remove_btrn:
 	btr_remove_node(&wn->btrn);
 	PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
-out:
 	t->error = ret;
 }