| Message ID | 20161201052422.18775-1-jiada_wang@mentor.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 12/01/2016 06:24 AM, Jiada Wang wrote: > 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> Thanks for the patch. Looks good to me. Reviewed-by: Lars-Peter Clausen <lars@metafoo.de> > --- > 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); > >
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);