Re: [alsa-devel] [PATCH] ASoC: fsl_audmix: Add spin lock to protect tdms

Hi

Hi Shengjiu,

Comments inline.

On Wed, Nov 6, 2019 at 9:30 AM Shengjiu Wang [off-list ref]
wrote:

quoted

Audmix support two substream, When two substream start to run, the
trigger function may be called by two substream in same time, that the
priv->tdms may be updated wrongly.

The expected priv->tdms is 0x3, but sometimes the result is 0x2, or
0x1.

Signed-off-by: Shengjiu Wang <redacted>
---
 sound/soc/fsl/fsl_audmix.c | 6 ++++++  sound/soc/fsl/fsl_audmix.h | 1
+
 2 files changed, 7 insertions(+)

diff --git a/sound/soc/fsl/fsl_audmix.c b/sound/soc/fsl/fsl_audmix.c
index c7e4e9757dce..a1db1bce330f 100644
--- a/sound/soc/fsl/fsl_audmix.c
+++ b/sound/soc/fsl/fsl_audmix.c

@@ -286,6 +286,7 @@ static int fsl_audmix_dai_trigger(struct

snd_pcm_substream *substream, int cmd,

quoted

                                  struct snd_soc_dai *dai)  {
        struct fsl_audmix *priv = snd_soc_dai_get_drvdata(dai);
+       unsigned long lock_flags;

        /* Capture stream shall not be handled */
        if (substream->stream == SNDRV_PCM_STREAM_CAPTURE)

@@ -295,12 +296,16 @@ static int fsl_audmix_dai_trigger(struct

snd_pcm_substream *substream, int cmd,

quoted

        case SNDRV_PCM_TRIGGER_START:
        case SNDRV_PCM_TRIGGER_RESUME:
        case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
+               spin_lock_irqsave(&priv->lock, lock_flags);

Why do we need to disable interrupts here? I assume that lock is only
used in process context.

It is in atomic context, so I think it is ok to disable interrupt. 

Best regards
Wang shengjiu

On Thu, Nov 7, 2019 at 8:54 AM S.j. Wang [off-list ref] wrote:

Hi

quoted

Hi Shengjiu,

Comments inline.

On Wed, Nov 6, 2019 at 9:30 AM Shengjiu Wang [off-list ref]
wrote:

quoted

Audmix support two substream, When two substream start to run, the
trigger function may be called by two substream in same time, that the
priv->tdms may be updated wrongly.

The expected priv->tdms is 0x3, but sometimes the result is 0x2, or
0x1.

Signed-off-by: Shengjiu Wang <redacted>
---
 sound/soc/fsl/fsl_audmix.c | 6 ++++++  sound/soc/fsl/fsl_audmix.h | 1
+
 2 files changed, 7 insertions(+)

diff --git a/sound/soc/fsl/fsl_audmix.c b/sound/soc/fsl/fsl_audmix.c
index c7e4e9757dce..a1db1bce330f 100644
--- a/sound/soc/fsl/fsl_audmix.c
+++ b/sound/soc/fsl/fsl_audmix.c

@@ -286,6 +286,7 @@ static int fsl_audmix_dai_trigger(struct

snd_pcm_substream *substream, int cmd,

quoted

                                  struct snd_soc_dai *dai)  {
        struct fsl_audmix *priv = snd_soc_dai_get_drvdata(dai);
+       unsigned long lock_flags;

        /* Capture stream shall not be handled */
        if (substream->stream == SNDRV_PCM_STREAM_CAPTURE)

@@ -295,12 +296,16 @@ static int fsl_audmix_dai_trigger(struct

snd_pcm_substream *substream, int cmd,

quoted

        case SNDRV_PCM_TRIGGER_START:
        case SNDRV_PCM_TRIGGER_RESUME:
        case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
+               spin_lock_irqsave(&priv->lock, lock_flags);

Why do we need to disable interrupts here? I assume that lock is only
used in process context.

It is in atomic context, so I think it is ok to disable interrupt.

All right thanks for the explanation. Added my Reviewed-by to v2.