linux-kernel - Re: [PATCH v1 1/2] ASoC: rsnd: ssi: fix race condition in rsnd_ssi_pointer

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Message-ID: <5A2A2494.2080202@mentor.com>
Date:   Thu, 7 Dec 2017 21:35:16 -0800
From:   Jiada Wang <jiada_wang@...tor.com>
To:     Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
CC:     <lgirdwood@...il.com>, <broonie@...nel.org>, <perex@...ex.cz>,
        <tiwai@...e.com>, <alsa-devel@...a-project.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 1/2] ASoC: rsnd: ssi: fix race condition in rsnd_ssi_pointer_update

Hello Morimoto-san

On 12/07/2017 01:45 AM, Kuninori Morimoto wrote:
> Hi Jiada
>
> Thank you for your patch
>
>> Currently there is race condition between set of byte_pos and wrap
>> it around when new buffer starts. If .pointer is called in-between
>> it will result in inconsistent pointer position be returned
>> from .pointer callback.
>>
>> This patch increments buffer pointer atomically to avoid this issue.
>>
>> Signed-off-by: Jiada Wang<jiada_wang@...tor.com>
>> Reviewed-by: Takashi Sakamoto<takashi.sakamoto@...aclelinux.com>
>> ---
> You using playback with PIO mode ?
> Because this function is no longer used on DMA mode
No, we are using rcar sound in DMA mode,
our original patch resolves the issue in core.c for both PIO & DMA mode.

but with your commit a97a06c ("ASoC: rsnd: cleanup pointer related code"),
DMA mode no longer has the race condition issue,
so I ported our fix patch to only address the issue in PIO mode

Thanks,
Jiada
> Best regards
> ---
> Kuninori Morimoto