ALSA: pcm_lib - return back hw_ptr_interrupt

Clemens Ladisch noted for hw_ptr_removal in "cleanup & merge hw_ptr
update functions" commit:

"It is possible for the status/delay ioctls to be called when the sound
card's pointer register alreay shows a position at the beginning of the
new period, but immediately before the interrupt is actually executed.
(This happens regularly on a SMP machine with mplayer.)  When that
happens, the code thinks that the position must be at least one period
ahead of the current position and drops an entire buffer of data."

Return back the hw_ptr_interrupt variable. The last interrupt pointer
is always computed from the latest hw_ptr instead of tracking it
separately (in this case all hw_ptr checks and modifications might
influence also hw_ptr_interrupt and it is difficult to keep it
consistent).

Signed-off-by: Jaroslav Kysela <perex@perex.cz>

1 files changed, 5 insertions, 2 deletions

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index e2a817eac2a..aa54195ef3b 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -325,8 +325,7 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
 	if (in_interrupt) {
 		/* we know that one period was processed */
 		/* delta = "expected next hw_ptr" for in_interrupt != 0 */
-		delta = old_hw_ptr - (old_hw_ptr % runtime->period_size)
-			+ runtime->period_size;
+		delta = runtime->hw_ptr_interrupt + runtime->period_size;
 		if (delta > new_hw_ptr) {
 			hw_base += runtime->buffer_size;
 			if (hw_base >= runtime->boundary)
@@ -437,6 +436,10 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
 	    runtime->silence_size > 0)
 		snd_pcm_playback_silence(substream, new_hw_ptr);
 
+	if (in_interrupt) {
+		runtime->hw_ptr_interrupt = new_hw_ptr -
+				(new_hw_ptr % runtime->period_size);
+	}
 	runtime->hw_ptr_base = hw_base;
 	runtime->status->hw_ptr = new_hw_ptr;
 	runtime->hw_ptr_jiffies = jiffies;