linux-kernel - Re: Applied "ASoC: rsnd: ssi: fix race condition in rsnd_ssi_pointer

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Message-ID: <661598a7-b62c-074a-a12e-12ed87f4700e@sakamocchi.jp>
Date:   Sat, 9 Dec 2017 14:22:50 +0900
From:   Takashi Sakamoto <o-takashi@...amocchi.jp>
To:     Mark Brown <broonie@...nel.org>, Jiada Wang <jiada_wang@...tor.com>
Cc:     alsa-devel@...a-project.org, kuninori.morimoto.gx@...esas.com,
        linux-kernel@...r.kernel.org, tiwai@...e.com, lgirdwood@...il.com
Subject: Re: Applied "ASoC: rsnd: ssi: fix race condition in
 rsnd_ssi_pointer_update" to the asoc tree

Hi Mark,

On Dec 9 2017 03:52, Mark Brown wrote:
> The patch
> 
>     ASoC: rsnd: ssi: fix race condition in rsnd_ssi_pointer_update
> 
> has been applied to the asoc tree at
> 
>     https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git

The applied patches are in v1 patchset, but we have v2 patchset already:
http://mailman.alsa-project.org/pipermail/alsa-devel/2017-December/128970.html

Would you please replace the applied patches with the renewed ones? 
There're slight differences between them.

> All being well this means that it will be integrated into the linux-next
> tree (usually sometime in the next 24 hours) and sent to Linus during
> the next merge window (or sooner if it is a bug fix), however if
> problems are discovered then the patch may be dropped or reverted.
> 
> You may get further e-mails resulting from automated or manual testing
> and review of the tree, please engage with people reporting problems and
> send followup patches addressing any issues that are reported if needed.
> 
> If any updates are required or you are submitting further changes they
> should be sent as incremental updates against current git, existing
> patches will not be replaced.
> 
> Please add any relevant lists and maintainers to the CCs when replying
> to this mail.
> 
> Thanks,
> Mark
> 
>>>From 33f801366bdf3f8b67dfe325b84f4051a090d01e Mon Sep 17 00:00:00 2001
> From: Jiada Wang <jiada_wang@...tor.com>
> Date: Thu, 7 Dec 2017 22:15:38 -0800
> Subject: [PATCH] ASoC: rsnd: ssi: fix race condition in
>   rsnd_ssi_pointer_update
> 
> 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>
> Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
> Signed-off-by: Mark Brown <broonie@...nel.org>
> ---
>   sound/soc/sh/rcar/ssi.c | 16 ++++++++++------
>   1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/sound/soc/sh/rcar/ssi.c b/sound/soc/sh/rcar/ssi.c
> index fece1e5f582f..cbf3bf312d23 100644
> --- a/sound/soc/sh/rcar/ssi.c
> +++ b/sound/soc/sh/rcar/ssi.c
> @@ -446,25 +446,29 @@ static bool rsnd_ssi_pointer_update(struct rsnd_mod *mod,
>   				    int byte)
>   {
>   	struct rsnd_ssi *ssi = rsnd_mod_to_ssi(mod);
> +	bool ret = false;
> +	int byte_pos;
>   
> -	ssi->byte_pos += byte;
> +	byte_pos = ssi->byte_pos + byte;
>   
> -	if (ssi->byte_pos >= ssi->next_period_byte) {
> +	if (byte_pos >= ssi->next_period_byte) {
>   		struct snd_pcm_runtime *runtime = rsnd_io_to_runtime(io);
>   
>   		ssi->period_pos++;
>   		ssi->next_period_byte += ssi->byte_per_period;
>   
>   		if (ssi->period_pos >= runtime->periods) {
> -			ssi->byte_pos = 0;
> +			byte_pos = 0;
>   			ssi->period_pos = 0;
>   			ssi->next_period_byte = ssi->byte_per_period;
>   		}
>   
> -		return true;
> +		ret = true;
>   	}
>   
> -	return false;
> +	WRITE_ONCE(ssi->byte_pos, byte_pos);
> +
> +	return ret;
>   }
>   
>   /*
> @@ -838,7 +842,7 @@ static int rsnd_ssi_pointer(struct rsnd_mod *mod,
>   	struct rsnd_ssi *ssi = rsnd_mod_to_ssi(mod);
>   	struct snd_pcm_runtime *runtime = rsnd_io_to_runtime(io);
>   
> -	*pointer = bytes_to_frames(runtime, ssi->byte_pos);
> +	*pointer = bytes_to_frames(runtime, READ_ONCE(ssi->byte_pos));
>   
>   	return 0;
>   }


Thanks

Takashi Sakamoto