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

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Message-ID: <CAEnQRZB0tXZvArgxL+u7x1RAWGyw8bDbGRF9u6tKiPjJbMpGkw@mail.gmail.com>
Date:   Wed, 6 Nov 2019 13:36:26 +0200
From:   Daniel Baluta <daniel.baluta@...il.com>
To:     Shengjiu Wang <shengjiu.wang@....com>
Cc:     Timur Tabi <timur@...nel.org>,
        Nicolin Chen <nicoleotsuka@...il.com>,
        Xiubo Li <Xiubo.Lee@...il.com>,
        Fabio Estevam <festevam@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Linux-ALSA <alsa-devel@...a-project.org>,
        linuxppc-dev@...ts.ozlabs.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [alsa-devel] [PATCH] ASoC: fsl_audmix: Add spin lock to protect tdms

Hi Shengjiu,

Comments inline.

On Wed, Nov 6, 2019 at 9:30 AM Shengjiu Wang <shengjiu.wang@....com> wrote:
>
> 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 <shengjiu.wang@....com>
> ---
>  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,
>                                   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,
>         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.

thanks,
Daniel.