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    Subject[PATCH 6.0 403/862] ALSA: dmaengine: increment buffer pointer atomically
    Date
    From: Andreas Pape <apape@de.adit-jv.com>

    [ Upstream commit d1c442019594692c64a70a86ad88eb5b6db92216 ]

    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 <apape@de.adit-jv.com>
    Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
    Link: https://lore.kernel.org/r/1664211493-11789-1-git-send-email-erosca@de.adit-jv.com
    Signed-off-by: Takashi Iwai <tiwai@suse.de>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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);
    }
    --
    2.35.1


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