linux-kernel - Re: [PATCH v2] dmaengine: altera-msgdma: correct mutex locking order

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Message-ID: <YpWE11ZI5MyyhtlD@olivier-3493erg>
Date:   Tue, 31 May 2022 05:00:39 +0200
From:   Olivier dautricourt <olivierdautricourt@...il.com>
To:     Nam Cao <namcaov@...il.com>
Cc:     vkoul@...nel.org, sr@...x.de, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] dmaengine: altera-msgdma: correct mutex locking order

On Sun, May 29, 2022 at 08:23:06PM +0200, Nam Cao wrote:
> The order of spin_unlock and spin_lock seems wrong. Correct it.
> 
> Signed-off-by: Nam Cao <namcaov@...il.com>
> ---
> Changes in v2:
> 	- Get rid of dirty index problem due to the patch being manually editted.
> 
>  drivers/dma/altera-msgdma.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/altera-msgdma.c b/drivers/dma/altera-msgdma.c
> index 6f56dfd375e3..e35096c12abc 100644
> --- a/drivers/dma/altera-msgdma.c
> +++ b/drivers/dma/altera-msgdma.c
> @@ -591,9 +591,9 @@ static void msgdma_chan_desc_cleanup(struct msgdma_device *mdev)
>  
>  		dmaengine_desc_get_callback(&desc->async_tx, &cb);
>  		if (dmaengine_desc_callback_valid(&cb)) {
> -			spin_unlock(&mdev->lock);
> -			dmaengine_desc_callback_invoke(&cb, NULL);
>  			spin_lock(&mdev->lock);
> +			dmaengine_desc_callback_invoke(&cb, NULL);
> +			spin_unlock(&mdev->lock);
>  		}
>  
>  		/* Run any dependencies, then free the descriptor */
> -- 
> 2.25.1
> 
Hello,

the lock is first grabbed in msgdma_tasklet.

Kr,

Olivier