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    Subject[PATCH 3/5] ASoC: stm32: sai: fix race condition in irq handler
    Date
    When snd_pcm_stop_xrun() is called in interrupt routine,
    substream context may have already been released.
    Add protection on substream context.

    Signed-off-by: Olivier Moysan <olivier.moysan@st.com>
    ---
    sound/soc/stm/stm32_sai_sub.c | 13 ++++++++++++-
    1 file changed, 12 insertions(+), 1 deletion(-)

    diff --git a/sound/soc/stm/stm32_sai_sub.c b/sound/soc/stm/stm32_sai_sub.c
    index e418f446e03b..cad415e03b5e 100644
    --- a/sound/soc/stm/stm32_sai_sub.c
    +++ b/sound/soc/stm/stm32_sai_sub.c
    @@ -102,6 +102,7 @@
    * @spdif_frm_cnt: S/PDIF playback frame counter
    * @iec958: iec958 data
    * @ctrl_lock: control lock
    + * @irq_lock: prevent race condition with IRQ
    */
    struct stm32_sai_sub_data {
    struct platform_device *pdev;
    @@ -133,6 +134,7 @@ struct stm32_sai_sub_data {
    unsigned int spdif_frm_cnt;
    struct snd_aes_iec958 iec958;
    struct mutex ctrl_lock; /* protect resources accessed by controls */
    + spinlock_t irq_lock; /* used to prevent race condition with IRQ */
    };

    enum stm32_sai_fifo_th {
    @@ -474,8 +476,10 @@ static irqreturn_t stm32_sai_isr(int irq, void *devid)
    status = SNDRV_PCM_STATE_XRUN;
    }

    - if (status != SNDRV_PCM_STATE_RUNNING)
    + spin_lock(&sai->irq_lock);
    + if (status != SNDRV_PCM_STATE_RUNNING && sai->substream)
    snd_pcm_stop_xrun(sai->substream);
    + spin_unlock(&sai->irq_lock);

    return IRQ_HANDLED;
    }
    @@ -679,8 +683,11 @@ static int stm32_sai_startup(struct snd_pcm_substream *substream,
    {
    struct stm32_sai_sub_data *sai = snd_soc_dai_get_drvdata(cpu_dai);
    int imr, cr2, ret;
    + unsigned long flags;

    + spin_lock_irqsave(&sai->irq_lock, flags);
    sai->substream = substream;
    + spin_unlock_irqrestore(&sai->irq_lock, flags);

    if (STM_SAI_PROTOCOL_IS_SPDIF(sai)) {
    snd_pcm_hw_constraint_mask64(substream->runtime,
    @@ -1059,6 +1066,7 @@ static void stm32_sai_shutdown(struct snd_pcm_substream *substream,
    struct snd_soc_dai *cpu_dai)
    {
    struct stm32_sai_sub_data *sai = snd_soc_dai_get_drvdata(cpu_dai);
    + unsigned long flags;

    regmap_update_bits(sai->regmap, STM_SAI_IMR_REGX, SAI_XIMR_MASK, 0);

    @@ -1069,7 +1077,9 @@ static void stm32_sai_shutdown(struct snd_pcm_substream *substream,

    clk_rate_exclusive_put(sai->sai_mclk);

    + spin_lock_irqsave(&sai->irq_lock, flags);
    sai->substream = NULL;
    + spin_unlock_irqrestore(&sai->irq_lock, flags);
    }

    static int stm32_sai_pcm_new(struct snd_soc_pcm_runtime *rtd,
    @@ -1433,6 +1443,7 @@ static int stm32_sai_sub_probe(struct platform_device *pdev)

    sai->pdev = pdev;
    mutex_init(&sai->ctrl_lock);
    + spin_lock_init(&sai->irq_lock);
    platform_set_drvdata(pdev, sai);

    sai->pdata = dev_get_drvdata(pdev->dev.parent);
    --
    2.7.4
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