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

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Message-ID: <AM0PR04MB6468D4D15E471940B1906344E3780@AM0PR04MB6468.eurprd04.prod.outlook.com>
Date:   Thu, 7 Nov 2019 06:54:16 +0000
From:   "S.j. Wang" <shengjiu.wang@....com>
To:     Daniel Baluta <daniel.baluta@...il.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" <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
> 
> 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.
> 
It is in atomic context, so I think it is ok to disable interrupt. 

Best regards
Wang shengjiu