linux-kernel - Re: [PATCH] ASoC: simple-card: Fix refcount underflow

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Date:   18 Feb 2019 10:17:22 +0900
From:   Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
To:     Daniel Baluta <daniel.baluta@....com>
Cc:     "broonie@...nel.org" <broonie@...nel.org>,
        "vicencb@...il.com" <vicencb@...il.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "tiwai@...e.com" <tiwai@...e.com>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        "S.j. Wang" <shengjiu.wang@....com>
Subject: Re: [PATCH] ASoC: simple-card: Fix refcount underflow


Hi Daniel, Mark

> of_get_child_by_name() takes a reference we'll need to drop
> later so when we substitute in top we need to take a reference
> as well as just assigning.
> 
> Without this patch we hit the following error:
> 
> [    1.246852] OF: ERROR: Bad of_node_put() on /sound-wm8524
> [    1.262261] Hardware name: NXP i.MX8MQ EVK (DT)
> [    1.266807] Workqueue: events deferred_probe_work_func
> [    1.271950] Call trace:
> [    1.274406]  dump_backtrace+0x0/0x158
> [    1.278074]  show_stack+0x14/0x20
> [    1.281396]  dump_stack+0xa8/0xcc
> [    1.284717]  of_node_release+0xb0/0xc8
> [    1.288474]  kobject_put+0x74/0xf0
> [    1.291879]  of_node_put+0x14/0x28
> [    1.295286]  __of_get_next_child+0x44/0x70
> [    1.299387]  of_get_next_child+0x3c/0x60
> [    1.303315]  simple_for_each_link+0x1dc/0x230
> [    1.307676]  simple_probe+0x80/0x540
> [    1.311256]  platform_drv_probe+0x50/0xa0
> 
> This patch is based on an earlier version posted by Kuninori Morimoto
> and commit message includes explanations from Mark Brown.
> 
> https://patchwork.kernel.org/patch/10814255/
> 
> Reported-by: Vicente Bergas <vicencb@...il.com>
> Signed-off-by: Daniel Baluta <daniel.baluta@....com>
> ---

I'm not sure which one is correct in this case

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>

or

Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>

>  sound/soc/generic/simple-card.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sound/soc/generic/simple-card.c b/sound/soc/generic/simple-card.c
> index 08df261024cf..dc18c4492955 100644
> --- a/sound/soc/generic/simple-card.c
> +++ b/sound/soc/generic/simple-card.c
> @@ -445,7 +445,7 @@ static int simple_for_each_link(struct simple_priv *priv,
>  	/* Check if it has dai-link */
>  	node = of_get_child_by_name(top, PREFIX "dai-link");
>  	if (!node) {
> -		node = top;
> +		node = of_node_get(top);
>  		is_top = 1;
>  	}
>  
> -- 
> 2.17.1
>