Subject: Re: [PATCH v3 4/8] DMA: Freescale: add fsl_dma_free_descriptor() to reduce code duplication

From: Andy Shevchenko <[email-masked]>
Date: Thu, 10 Apr 2014 14:29:21 +0300

On Thu, 2014-04-10 at 15:10 +0800, [email-masked] wrote:
> From: Hongbo Zhang <[email-masked]>
> 
> There are several places where descriptors are freed using identical code.
> This patch puts this code into a function to reduce code duplication.
> 
> Signed-off-by: Hongbo Zhang <[email-masked]>
> Signed-off-by: Qiang Liu <[email-masked]>
> ---
>  drivers/dma/fsldma.c |   30 ++++++++++++++++++------------
>  1 file changed, 18 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/dma/fsldma.c b/drivers/dma/fsldma.c
> index b71cc04..b5a0ffa 100644
> --- a/drivers/dma/fsldma.c
> +++ b/drivers/dma/fsldma.c
> @@ -418,6 +418,19 @@ static dma_cookie_t fsl_dma_tx_submit(struct dma_async_tx_descriptor *tx)
>  }
>  
>  /**
> + * fsl_dma_free_descriptor - Free descriptor from channel's DMA pool.
> + * @chan : Freescale DMA channel
> + * @desc: descriptor to be freed
> + */
> +static void fsl_dma_free_descriptor(struct fsldma_chan *chan,
> +		struct fsl_desc_sw *desc)
> +{
> +	list_del(&desc->node);
> +	chan_dbg(chan, "LD %p free\n", desc);
> +	dma_pool_free(chan->desc_pool, desc, desc->async_tx.phys);
> +}
> +
> +/**
>   * fsl_dma_alloc_descriptor - Allocate descriptor from channel's DMA pool.
>   * @chan : Freescale DMA channel
>   *
> @@ -489,11 +502,8 @@ static void fsldma_free_desc_list(struct fsldma_chan *chan,
>  {
>  	struct fsl_desc_sw *desc, *_desc;
>  
> -	list_for_each_entry_safe(desc, _desc, list, node) {
> -		list_del(&desc->node);
> -		chan_dbg(chan, "LD %p free\n", desc);
> -		dma_pool_free(chan->desc_pool, desc, desc->async_tx.phys);
> -	}
> +	list_for_each_entry_safe(desc, _desc, list, node)
> +		fsl_dma_free_descriptor(chan, desc);
>  }
>  
>  static void fsldma_free_desc_list_reverse(struct fsldma_chan *chan,
> @@ -501,11 +511,8 @@ static void fsldma_free_desc_list_reverse(struct fsldma_chan *chan,
>  {
>  	struct fsl_desc_sw *desc, *_desc;
>  
> -	list_for_each_entry_safe_reverse(desc, _desc, list, node) {
> -		list_del(&desc->node);
> -		chan_dbg(chan, "LD %p free\n", desc);
> -		dma_pool_free(chan->desc_pool, desc, desc->async_tx.phys);
> -	}
> +	list_for_each_entry_safe_reverse(desc, _desc, list, node)
> +		fsl_dma_free_descriptor(chan, desc);
>  }
>  
>  /**
> @@ -819,8 +826,7 @@ static void fsldma_cleanup_descriptor(struct fsldma_chan *chan,
>  	dma_run_dependencies(txd);
>  
>  	dma_descriptor_unmap(txd);
> -	chan_dbg(chan, "LD %p free\n", desc);
> -	dma_pool_free(chan->desc_pool, desc, txd->phys);
> +	fsl_dma_free_descriptor(chan, desc);

Here is no list_del() call since it's been called in dma_do_tasklet().
What will be the result of double list_del() against the same node?

>  }
>  /**

-- 
Andy Shevchenko <[email-masked]>
Intel Finland Oy