From 1c6fa9aa4483c491c4edf0129bc26478513324ed Mon Sep 17 00:00:00 2001 From: Andre Noll Date: Thu, 14 Jun 2012 13:26:32 +0200 Subject: [PATCH] osx_write: Add big fat comment on callback btr node. --- osx_write.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/osx_write.c b/osx_write.c index 8dcfb4cd..e34f0388 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; }; -- 2.39.2