[alsa-devel] [PATCH 12/49] firewire-lib: Restrict calling flush_context_completion() when context exists

[Takashi Sakamoto]

Currently, drivers can bring XRUN state for PCM substreams when error to
queue packets or detecting discontinuity of packet. The application may try to
recover this state by calling snd_pcm_prepare().

Depending on each driver, .prepare() includes restart streaming. Then there
is a state that PCM substreams are running but isochronous contexts are
stopped. In this case, when .pointer() is called, it refers to error pointer.

This commit is for a prevention of this bug.

Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
---
 sound/firewire/amdtp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/firewire/amdtp.c b/sound/firewire/amdtp.c
index ac8c358..7c814ace 100644
--- a/sound/firewire/amdtp.c
+++ b/sound/firewire/amdtp.c
@@ -898,7 +898,7 @@ EXPORT_SYMBOL(amdtp_stream_start);
 unsigned long amdtp_stream_pcm_pointer(struct amdtp_stream *s)
 {
 	/* this optimization is allowed to be racy */
-	if (s->pointer_flush)
+	if (s->pointer_flush && amdtp_stream_running(s))
 		fw_iso_context_flush_completions(s->context);
 	else
 		s->pointer_flush = true;
-- 
1.8.3.2