2022-09-26 18:19:13

by Eugeniu Rosca

Subject: [PATCH] ALSA: dmaengine: increment buffer pointer atomically

From: Andreas Pape <[email protected]>

Setting pointer and afterwards checking for wraparound leads
to the possibility of returning the inconsistent pointer position.

This patch increments buffer pointer atomically to avoid this issue.

Fixes: e7f73a1613567a ("ASoC: Add dmaengine PCM helper functions")
Signed-off-by: Andreas Pape <[email protected]>
Signed-off-by: Eugeniu Rosca <[email protected]>
---
sound/core/pcm_dmaengine.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/sound/core/pcm_dmaengine.c b/sound/core/pcm_dmaengine.c
index 5b2ca028f5aa..494ec0c207fa 100644
--- a/sound/core/pcm_dmaengine.c
+++ b/sound/core/pcm_dmaengine.c
@@ -133,12 +133,14 @@ EXPORT_SYMBOL_GPL(snd_dmaengine_pcm_set_config_from_dai_data);

static void dmaengine_pcm_dma_complete(void *arg)
{
+ unsigned int new_pos;
struct snd_pcm_substream *substream = arg;
struct dmaengine_pcm_runtime_data *prtd = substream_to_prtd(substream);

- prtd->pos += snd_pcm_lib_period_bytes(substream);
- if (prtd->pos >= snd_pcm_lib_buffer_bytes(substream))
- prtd->pos = 0;
+ new_pos = prtd->pos + snd_pcm_lib_period_bytes(substream);
+ if (new_pos >= snd_pcm_lib_buffer_bytes(substream))
+ new_pos = 0;
+ prtd->pos = new_pos;

snd_pcm_period_elapsed(substream);
}
--
2.37.2

2022-09-27 07:06:26

by Takashi Iwai

Subject: Re: [PATCH] ALSA: dmaengine: increment buffer pointer atomically

On Mon, 26 Sep 2022 18:58:13 +0200,
Eugeniu Rosca wrote:
>
> From: Andreas Pape <[email protected]>
>
> Setting pointer and afterwards checking for wraparound leads
> to the possibility of returning the inconsistent pointer position.
>
> This patch increments buffer pointer atomically to avoid this issue.
>
> Fixes: e7f73a1613567a ("ASoC: Add dmaengine PCM helper functions")
> Signed-off-by: Andreas Pape <[email protected]>
> Signed-off-by: Eugeniu Rosca <[email protected]>

Thanks, applied.


Takashi