linux-kernel - Re: [PATCH v14 12/12] dmaengine: imx-sdma: add terminated list for freed descriptor in worker

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Date:   Fri, 09 Jul 2021 11:55:39 +0200
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Robin Gong <yibin.gong@....com>, vkoul@...nel.org,
        mark.rutland@....com, broonie@...nel.org, robh+dt@...nel.org,
        catalin.marinas@....com, will.deacon@....com, shawnguo@...nel.org,
        festevam@...il.com, s.hauer@...gutronix.de,
        martin.fuzzey@...wbird.group, u.kleine-koenig@...gutronix.de,
        dan.j.williams@...el.com, matthias.schiffer@...tq-group.com,
        frieder.schrempf@...tron.de, m.felsch@...gutronix.de,
        xiaoning.wang@....com
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-spi@...r.kernel.org, linux-imx@....com,
        kernel@...gutronix.de, dmaengine@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v14 12/12] dmaengine: imx-sdma: add terminated list for
 freed descriptor in worker

Am Mittwoch, dem 07.04.2021 um 23:30 +0800 schrieb Robin Gong:
> Add terminated list for keeping descriptor so that it could be freed in
> worker without any potential involving next descriptor raised up before
> this descriptor freed, because vchan_get_all_descriptors get all
> descriptors including the last terminated descriptor and the next
> descriptor, hence, the next descriptor maybe freed unexpectly when it's
> done in worker without this patch.
> https://www.spinics.net/lists/dmaengine/msg23367.html
> 
> Signed-off-by: Robin Gong <yibin.gong@....com>
> Reported-by: Richard Leitner <richard.leitner@...data.com>

Reviewed-by: Lucas Stach <l.stach@...gutronix.de>

> ---
>  drivers/dma/imx-sdma.c | 17 ++++++++++-------
>  1 file changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
> index 9519b41..4174580 100644
> --- a/drivers/dma/imx-sdma.c
> +++ b/drivers/dma/imx-sdma.c
> @@ -381,6 +381,7 @@ struct sdma_channel {
>  	enum dma_status			status;
>  	struct imx_dma_data		data;
>  	struct work_struct		terminate_worker;
> +	struct list_head                terminated;
>  	bool				is_ram_script;
>  };
>  
> @@ -1041,9 +1042,6 @@ static void sdma_channel_terminate_work(struct work_struct *work)
>  {
>  	struct sdma_channel *sdmac = container_of(work, struct sdma_channel,
>  						  terminate_worker);
> -	unsigned long flags;
> -	LIST_HEAD(head);
> -
>  	/*
>  	 * According to NXP R&D team a delay of one BD SDMA cost time
>  	 * (maximum is 1ms) should be added after disable of the channel
> @@ -1052,10 +1050,7 @@ static void sdma_channel_terminate_work(struct work_struct *work)
>  	 */
>  	usleep_range(1000, 2000);
>  
> -	spin_lock_irqsave(&sdmac->vc.lock, flags);
> -	vchan_get_all_descriptors(&sdmac->vc, &head);
> -	spin_unlock_irqrestore(&sdmac->vc.lock, flags);
> -	vchan_dma_desc_free_list(&sdmac->vc, &head);
> +	vchan_dma_desc_free_list(&sdmac->vc, &sdmac->terminated);
>  }
>  
>  static int sdma_terminate_all(struct dma_chan *chan)
> @@ -1069,6 +1064,13 @@ static int sdma_terminate_all(struct dma_chan *chan)
>  
>  	if (sdmac->desc) {
>  		vchan_terminate_vdesc(&sdmac->desc->vd);
> +		/*
> +		 * move out current descriptor into terminated list so that
> +		 * it could be free in sdma_channel_terminate_work alone
> +		 * later without potential involving next descriptor raised
> +		 * up before the last descriptor terminated.
> +		 */
> +		vchan_get_all_descriptors(&sdmac->vc, &sdmac->terminated);
>  		sdmac->desc = NULL;
>  		schedule_work(&sdmac->terminate_worker);
>  	}
> @@ -2075,6 +2077,7 @@ static int sdma_probe(struct platform_device *pdev)
>  
>  		sdmac->channel = i;
>  		sdmac->vc.desc_free = sdma_desc_free;
> +		INIT_LIST_HEAD(&sdmac->terminated);
>  		INIT_WORK(&sdmac->terminate_worker,
>  				sdma_channel_terminate_work);
>  		/*