linux-kernel - Re: [PATCH 5.10 012/105] dmaengine: shdma: Fix runtime PM imbalance on error

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Date:   Wed, 9 Mar 2022 11:54:20 +0100
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Yongzhi Liu <lyz_cs@....edu.cn>, Vinod Koul <vkoul@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.10 012/105] dmaengine: shdma: Fix runtime PM imbalance
 on error

Hi!

> From: Yongzhi Liu <lyz_cs@....edu.cn>
> 
> [ Upstream commit 455896c53d5b803733ddd84e1bf8a430644439b6 ]
> 
> pm_runtime_get_() increments the runtime PM usage counter even
> when it returns an error code, thus a matching decrement is needed on
> the error handling path to keep the counter balanced.

This patch will break things.

Notice that -ret is ignored (checked 4.4 and 5.10), so we don't
actually abort/return error; we just printk. We'll do two
pm_runtime_put's after the "fix".

Please drop from -stable.

It was discussed during AUTOSEL review:

Date: Fri, 25 Feb 2022 14:25:10 +0800 (GMT+08:00)
From: 刘永志 <lyz_cs@....edu.cn>
To: pavel machek <pavel@...x.de>
Cc: sasha levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
Subject: Re: [PATCH AUTOSEL 5.16 24/30] dmaengine: shdma: Fix runtime PM
	imbalance on error

Best regards,
	                                                        Pavel

> +++ b/drivers/dma/sh/shdma-base.c
> @@ -115,8 +115,10 @@ static dma_cookie_t shdma_tx_submit(struct dma_async_tx_descriptor *tx)
>  		ret = pm_runtime_get(schan->dev);
>  
>  		spin_unlock_irq(&schan->chan_lock);
> -		if (ret < 0)
> +		if (ret < 0) {
>  			dev_err(schan->dev, "%s(): GET = %d\n", __func__, ret);
> +			pm_runtime_put(schan->dev);
> +		}
>  
>  		pm_runtime_barrier(schan->dev);
>  
> -- 
> 2.34.1
> 
> 

-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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