Messages in this thread Patch in this message | | | From | Jiada Wang <> | Subject | [PATCH v2 1/1] ALSA: SOC: DMA: access buffer pointer atomically | Date | Thu, 1 Dec 2016 14:24:22 +0900 |
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From: Andreas Pape <apape@de.adit-jv.com>
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@de.adit-jv.com> Signed-off-by: Jiada Wang <jiada_wang@mentor.com> --- 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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