linux-kernel - Re: [PATCH 2/3] sound: enable interrupt after dma buffer initialization

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Date:   Tue, 11 Sep 2018 14:58:25 -0600
From:   Yu Zhao <yuzhao@...gle.com>
To:     Takashi Iwai <tiwai@...e.de>, Vinod Koul <vkoul@...nel.org>
Cc:     Mark Brown <broonie@...nel.org>, alsa-devel@...a-project.org,
        Rakesh Ughreja <rakesh.a.ughreja@...el.com>,
        Jaroslav Kysela <perex@...ex.cz>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] sound: enable interrupt after dma buffer
 initialization

On Tue, Sep 11, 2018 at 08:06:49AM +0200, Takashi Iwai wrote:
> On Mon, 10 Sep 2018 23:21:50 +0200,
> Yu Zhao wrote:
> > 
> > In snd_hdac_bus_init_chip(), we enable interrupt before
> > snd_hdac_bus_init_cmd_io() initializing dma buffers. If irq has
> > been acquired and irq handler uses the dma buffer, kernel may crash
> > when interrupt comes in.
> > 
> > Fix the problem by postponing enabling irq after dma buffer
> > initialization. And warn once on null dma buffer pointer during the
> > initialization.
> > 
> > Signed-off-by: Yu Zhao <yuzhao@...gle.com>
> 
> Looks good to me.
> 
> Reviewed-by: Takashi Iwai <tiwai@...e.de>
> 
> 
> BTW, the reason why this hasn't been hit on the legacy HD-audio driver
> is that we allocate usually with MSI, so the irq is isolated.
> 
> Any reason that Intel SKL driver doesn't use MST?

This I'm not sure. Vinod might have answer to it, according to
https://patchwork.kernel.org/patch/6375831/#13796611