From: Andreas Pape <apape@xxxxxxxxxxxxxx>
Setting pointer and afterwards check for wrap around leads
to the possibility of returning the inconsistent pointer position.
This patch accesses buffer pointer atomically to avoid this issue.
v2: use READ_ONCE and WRITE_ONCE to ensure read/write of buffer pointer in
only one access
also updates snd_dmaengine_pcm_pointer_no_residue to ensure atomic
access
Signed-off-by: Andreas Pape <apape@xxxxxxxxxxxxxx>
Signed-off-by: Jiada Wang <jiada_wang@xxxxxxxxxx>
---
sound/core/pcm_dmaengine.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/sound/core/pcm_dmaengine.c b/sound/core/pcm_dmaengine.c
index 8eb58c7..b6255fd 100644
--- a/sound/core/pcm_dmaengine.c
+++ b/sound/core/pcm_dmaengine.c
@@ -139,12 +139,14 @@ 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;
+ WRITE_ONCE(prtd->pos, new_pos);
snd_pcm_period_elapsed(substream);
}
@@ -235,7 +237,7 @@ EXPORT_SYMBOL_GPL(snd_dmaengine_pcm_trigger);
snd_pcm_uframes_t snd_dmaengine_pcm_pointer_no_residue(struct snd_pcm_substream *substream)
{
struct dmaengine_pcm_runtime_data *prtd = substream_to_prtd(substream);
- return bytes_to_frames(substream->runtime, prtd->pos);
+ return bytes_to_frames(substream->runtime, READ_ONCE(prtd->pos));
}
EXPORT_SYMBOL_GPL(snd_dmaengine_pcm_pointer_no_residue);
--
2.9.3
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