Re: [PATCH] dmaengine: usb-dmac: fix endless loop in usb_dmac_chan_terminate_all()

[Vinod Koul <vinod.koul@intel.com>]

On Thu, Nov 12, 2015 at 01:37:40PM +0900, Yoshihiro Shimoda wrote:
> This patch fixes an issue that list_for_each_entry() in
> usb_dmac_chan_terminate_all() is possible to cause endless loop because
> this will move own desc to the desc_freed. So, this driver should use
> list_for_each_entry_safe() instead of list_for_each_entry().

Sorry this is not clear to my why this owuld have endless loop, can you
explain more

> 
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> ---
>  drivers/dma/sh/usb-dmac.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/sh/usb-dmac.c b/drivers/dma/sh/usb-dmac.c
> index ebd8a5f..16fb330 100644
> --- a/drivers/dma/sh/usb-dmac.c
> +++ b/drivers/dma/sh/usb-dmac.c
> @@ -448,7 +448,7 @@ usb_dmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
>  static int usb_dmac_chan_terminate_all(struct dma_chan *chan)
>  {
>  	struct usb_dmac_chan *uchan = to_usb_dmac_chan(chan);
> -	struct usb_dmac_desc *desc;
> +	struct usb_dmac_desc *desc, *_desc;
>  	unsigned long flags;
>  	LIST_HEAD(head);
>  	LIST_HEAD(list);
> @@ -459,7 +459,7 @@ static int usb_dmac_chan_terminate_all(struct dma_chan *chan)
>  	if (uchan->desc)
>  		uchan->desc = NULL;
>  	list_splice_init(&uchan->desc_got, &list);
> -	list_for_each_entry(desc, &list, node)
> +	list_for_each_entry_safe(desc, _desc, &list, node)
>  		list_move_tail(&desc->node, &uchan->desc_freed);
>  	spin_unlock_irqrestore(&uchan->vc.lock, flags);
>  	vchan_dma_desc_free_list(&uchan->vc, &head);
> -- 
> 1.9.1
> 
> --
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-- 
~Vinod