linux-kernel - Re: [PATCH v3] ASoC: amd: acp: Initialize list to store acp_stream during pcm

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Message-ID: <87sfmkp520.wl-tiwai@suse.de>
Date:   Fri, 29 Jul 2022 12:49:11 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Venkata Prasad Potturu <venkataprasad.potturu@....com>
Cc:     Mark Brown <broonie@...nel.org>, alsa-devel@...a-project.org,
        vsujithkumar.reddy@....com, Vijendar.Mukunda@....com,
        Basavaraj.Hiregoudar@....com, Sunil-kumar.Dommati@....com,
        ssabakar@....com, Ajit Kumar Pandey <AjitKumar.Pandey@....com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Yang Yingliang <yangyingliang@...wei.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Charles Keepax <ckeepax@...nsource.cirrus.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] ASoC: amd: acp: Initialize list to store acp_stream during pcm_open

On Fri, 29 Jul 2022 12:34:51 +0200,
Venkata Prasad Potturu wrote:
> 
> 
> On 7/28/22 18:19, Mark Brown wrote:
> Thanks for your time.
> 
>     On Thu, Jul 28, 2022 at 06:10:50PM +0530, Venkata Prasad Potturu wrote:
> 
>         @@ -104,14 +105,13 @@ static irqreturn_t i2s_irq_handler(int irq, void *data)
>          
>               ext_intr_stat = readl(ACP_EXTERNAL_INTR_STAT(adata, rsrc->irqp_used));
>          
>         -     for (i = 0; i < ACP_MAX_STREAM; i++) {
>         -                           stream = adata->stream[i];
>         +     spin_lock_irqsave(&adata->acp_lock, flags);
>         +     list_for_each_entry(stream, &adata->stream_list, list) {
>         
>     If we're already in an interrupt handler here (presumably not a threaded
>     one) why are we using irqsave?
>     
> Yes, your statement make sense, I have followed below statement in kernel
> document. so used irqsave in interrupt context as well.
> 
> We will change it to spin_lock() and send it in the next version.
> 
> statement:- spin_lock_irqsave() will turn off interrupts if they are on,
> otherwise does nothing (if we are already in an interrupt handler), hence
> these functions are safe to call from any context.

Also the open and close callbacks are certainly non-irq context, hence
you can use spin_lock_irq() instead of irqsave(), too.


Takashi