linux-kernel - Re: [PATCH v2] drivers/dma/dma-jz4780: Fix race condition between probe and irq handler

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Message-Id: <9BBFFQ.4DKVQYU5BDCT1@crapouillou.net>
Date:   Fri, 21 Aug 2020 19:01:57 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     madhuparnabhowmik10@...il.com
Cc:     vkoul@...nel.org, dan.j.williams@...el.com, lars@...afoo.de,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        andrianov@...ras.ru, ldv-project@...uxtesting.org
Subject: Re: [PATCH v2] drivers/dma/dma-jz4780: Fix race condition between
 probe and irq handler



Le ven. 21 août 2020 à 9:14, madhuparnabhowmik10@...il.com a écrit :
> From: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
> 
> In probe, IRQ is requested before zchan->id is initialized which can 
> be
> read in the irq handler. Hence, shift request irq after other 
> initializations
> complete.
> 
> Found by Linux Driver Verification project (linuxtesting.org).
> 
> Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>

Reviewed-by: Paul Cercueil <paul@...pouillou.net>

Thanks for the patch.

Cheers,
-Paul

> 
> ---
> Changes since v1:
> Keep enable clock before request IRQ.
> ---
>  drivers/dma/dma-jz4780.c | 38 +++++++++++++++++++-------------------
>  1 file changed, 19 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/dma/dma-jz4780.c b/drivers/dma/dma-jz4780.c
> index 448f663da89c..8beed91428bd 100644
> --- a/drivers/dma/dma-jz4780.c
> +++ b/drivers/dma/dma-jz4780.c
> @@ -879,24 +879,11 @@ static int jz4780_dma_probe(struct 
> platform_device *pdev)
>  		return -EINVAL;
>  	}
> 
> -	ret = platform_get_irq(pdev, 0);
> -	if (ret < 0)
> -		return ret;
> -
> -	jzdma->irq = ret;
> -
> -	ret = request_irq(jzdma->irq, jz4780_dma_irq_handler, 0, 
> dev_name(dev),
> -			  jzdma);
> -	if (ret) {
> -		dev_err(dev, "failed to request IRQ %u!\n", jzdma->irq);
> -		return ret;
> -	}
> -
>  	jzdma->clk = devm_clk_get(dev, NULL);
>  	if (IS_ERR(jzdma->clk)) {
>  		dev_err(dev, "failed to get clock\n");
>  		ret = PTR_ERR(jzdma->clk);
> -		goto err_free_irq;
> +		return ret;
>  	}
> 
>  	clk_prepare_enable(jzdma->clk);
> @@ -949,10 +936,23 @@ static int jz4780_dma_probe(struct 
> platform_device *pdev)
>  		jzchan->vchan.desc_free = jz4780_dma_desc_free;
>  	}
> 
> +	ret = platform_get_irq(pdev, 0);
> +	if (ret < 0)
> +		goto err_disable_clk;
> +
> +	jzdma->irq = ret;
> +
> +	ret = request_irq(jzdma->irq, jz4780_dma_irq_handler, 0, 
> dev_name(dev),
> +			  jzdma);
> +	if (ret) {
> +		dev_err(dev, "failed to request IRQ %u!\n", jzdma->irq);
> +		goto err_disable_clk;
> +	}
> +
>  	ret = dmaenginem_async_device_register(dd);
>  	if (ret) {
>  		dev_err(dev, "failed to register device\n");
> -		goto err_disable_clk;
> +		goto err_free_irq;
>  	}
> 
>  	/* Register with OF DMA helpers. */
> @@ -960,17 +960,17 @@ static int jz4780_dma_probe(struct 
> platform_device *pdev)
>  					 jzdma);
>  	if (ret) {
>  		dev_err(dev, "failed to register OF DMA controller\n");
> -		goto err_disable_clk;
> +		goto err_free_irq;
>  	}
> 
>  	dev_info(dev, "JZ4780 DMA controller initialised\n");
>  	return 0;
> 
> -err_disable_clk:
> -	clk_disable_unprepare(jzdma->clk);
> -
>  err_free_irq:
>  	free_irq(jzdma->irq, jzdma);
> +
> +err_disable_clk:
> +	clk_disable_unprepare(jzdma->clk);
>  	return ret;
>  }
> 
> --
> 2.17.1
>