linux-kernel - [PATCH 4.9 30/42] ALSA: aloop: Fix random zeros in capture data when using jiffies timer

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Date:   Tue, 13 Sep 2022 16:08:01 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Pattara Teerapong <pteerapong@...omium.org>,
        Takashi Iwai <tiwai@...e.de>
Subject: [PATCH 4.9 30/42] ALSA: aloop: Fix random zeros in capture data when using jiffies timer

From: Pattara Teerapong <pteerapong@...omium.org>

commit 3e48940abee88b8dbbeeaf8a07e7b2b6be1271b3 upstream.

In loopback_jiffies_timer_pos_update(), we are getting jiffies twice.
First time for playback, second time for capture. Jiffies can be updated
between these two calls and if the capture jiffies is larger, extra zeros
will be filled in the capture buffer.

Change to get jiffies once and use it for both playback and capture.

Signed-off-by: Pattara Teerapong <pteerapong@...omium.org>
Cc: <stable@...r.kernel.org>
Link: https://lore.kernel.org/r/20220901144036.4049060-1-pteerapong@chromium.org
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 sound/drivers/aloop.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/sound/drivers/aloop.c
+++ b/sound/drivers/aloop.c
@@ -477,17 +477,18 @@ static unsigned int loopback_pos_update(
 			cable->streams[SNDRV_PCM_STREAM_PLAYBACK];
 	struct loopback_pcm *dpcm_capt =
 			cable->streams[SNDRV_PCM_STREAM_CAPTURE];
-	unsigned long delta_play = 0, delta_capt = 0;
+	unsigned long delta_play = 0, delta_capt = 0, cur_jiffies;
 	unsigned int running, count1, count2;
 
+	cur_jiffies = jiffies;
 	running = cable->running ^ cable->pause;
 	if (running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) {
-		delta_play = jiffies - dpcm_play->last_jiffies;
+		delta_play = cur_jiffies - dpcm_play->last_jiffies;
 		dpcm_play->last_jiffies += delta_play;
 	}
 
 	if (running & (1 << SNDRV_PCM_STREAM_CAPTURE)) {
-		delta_capt = jiffies - dpcm_capt->last_jiffies;
+		delta_capt = cur_jiffies - dpcm_capt->last_jiffies;
 		dpcm_capt->last_jiffies += delta_capt;
 	}