On Fri, Apr 22, 2016 at 01:50:04AM +0000, Kuninori Morimoto wrote: > > From: Kuninori Morimoto <kuninori.morimoto...@renesas.com> > > Current rcar_dmac_desc_put() is using list_add_tail() in order to > push used descriptor to list of free descriptors, and next DMA transfer > try to reuse it from this list. But because it is using *_tail(), > this reuse effect can't be obtained without using all of them. > For a longer-term solution, we should allocate hardware descriptors > using GFP_KERNEL instead of GFP_NOWAIT, but it is difficult today. > This patch uses list_add() instead of list_add_tail() for short-term > solution.
So how does reuse case help by not moving the descriptor to tail. Also you are not reusing descriptor, you are reusing a descriptor memory, these are two different things. Lastly how does this help? Something doesn't seem right > > Signed-off-by: Kuninori Morimoto <kuninori.morimoto...@renesas.com> > --- > drivers/dma/sh/rcar-dmac.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c > index 02b86c6..616c63a 100644 > --- a/drivers/dma/sh/rcar-dmac.c > +++ b/drivers/dma/sh/rcar-dmac.c > @@ -519,7 +519,7 @@ static void rcar_dmac_desc_put(struct rcar_dmac_chan > *chan, > > spin_lock_irqsave(&chan->lock, flags); > list_splice_tail_init(&desc->chunks, &chan->desc.chunks_free); > - list_add_tail(&desc->node, &chan->desc.free); > + list_add(&desc->node, &chan->desc.free); > spin_unlock_irqrestore(&chan->lock, flags); > } > -- ~Vinod
