On Wed, Oct 27, 2010 at 01:52:58AM +0200, Ilya Yanok wrote:
> Currently completed descriptors are processed in the tasklet. This can
> lead to dead lock in case of CONFIG_NET_DMA enabled (new requests are
> submitted from softirq context and dma_memcpy_to_iovec() busy loops until
> the requests is submitted). To prevent this we should process completed
> descriptors from the allocation failure path in prepare_memcpy too.
>
> Signed-off-by: Ilya Yanok <ya...@emcraft.com>
> Cc: Piotr Ziecik <ko...@semihalf.com>
Merged for -next, thanks.
g.
> ---
> drivers/dma/mpc512x_dma.c | 79 +++++++++++++++++++++++++-------------------
> 1 files changed, 45 insertions(+), 34 deletions(-)
>
> diff --git a/drivers/dma/mpc512x_dma.c b/drivers/dma/mpc512x_dma.c
> index 97b92ec..59c2701 100644
> --- a/drivers/dma/mpc512x_dma.c
> +++ b/drivers/dma/mpc512x_dma.c
> @@ -328,19 +328,55 @@ static irqreturn_t mpc_dma_irq(int irq, void *data)
> return IRQ_HANDLED;
> }
>
> -/* DMA Tasklet */
> -static void mpc_dma_tasklet(unsigned long data)
> +/* proccess completed descriptors */
> +static void mpc_dma_process_completed(struct mpc_dma *mdma)
> {
> - struct mpc_dma *mdma = (void *)data;
> dma_cookie_t last_cookie = 0;
> struct mpc_dma_chan *mchan;
> struct mpc_dma_desc *mdesc;
> struct dma_async_tx_descriptor *desc;
> unsigned long flags;
> LIST_HEAD(list);
> - uint es;
> int i;
>
> + for (i = 0; i < mdma->dma.chancnt; i++) {
> + mchan = &mdma->channels[i];
> +
> + /* Get all completed descriptors */
> + spin_lock_irqsave(&mchan->lock, flags);
> + if (!list_empty(&mchan->completed))
> + list_splice_tail_init(&mchan->completed, &list);
> + spin_unlock_irqrestore(&mchan->lock, flags);
> +
> + if (list_empty(&list))
> + continue;
> +
> + /* Execute callbacks and run dependencies */
> + list_for_each_entry(mdesc, &list, node) {
> + desc = &mdesc->desc;
> +
> + if (desc->callback)
> + desc->callback(desc->callback_param);
> +
> + last_cookie = desc->cookie;
> + dma_run_dependencies(desc);
> + }
> +
> + /* Free descriptors */
> + spin_lock_irqsave(&mchan->lock, flags);
> + list_splice_tail_init(&list, &mchan->free);
> + mchan->completed_cookie = last_cookie;
> + spin_unlock_irqrestore(&mchan->lock, flags);
> + }
> +}
> +
> +/* DMA Tasklet */
> +static void mpc_dma_tasklet(unsigned long data)
> +{
> + struct mpc_dma *mdma = (void *)data;
> + unsigned long flags;
> + uint es;
> +
> spin_lock_irqsave(&mdma->error_status_lock, flags);
> es = mdma->error_status;
> mdma->error_status = 0;
> @@ -379,35 +415,7 @@ static void mpc_dma_tasklet(unsigned long data)
> dev_err(mdma->dma.dev, "- Destination Bus Error\n");
> }
>
> - for (i = 0; i < mdma->dma.chancnt; i++) {
> - mchan = &mdma->channels[i];
> -
> - /* Get all completed descriptors */
> - spin_lock_irqsave(&mchan->lock, flags);
> - if (!list_empty(&mchan->completed))
> - list_splice_tail_init(&mchan->completed, &list);
> - spin_unlock_irqrestore(&mchan->lock, flags);
> -
> - if (list_empty(&list))
> - continue;
> -
> - /* Execute callbacks and run dependencies */
> - list_for_each_entry(mdesc, &list, node) {
> - desc = &mdesc->desc;
> -
> - if (desc->callback)
> - desc->callback(desc->callback_param);
> -
> - last_cookie = desc->cookie;
> - dma_run_dependencies(desc);
> - }
> -
> - /* Free descriptors */
> - spin_lock_irqsave(&mchan->lock, flags);
> - list_splice_tail_init(&list, &mchan->free);
> - mchan->completed_cookie = last_cookie;
> - spin_unlock_irqrestore(&mchan->lock, flags);
> - }
> + mpc_dma_process_completed(mdma);
> }
>
> /* Submit descriptor to hardware */
> @@ -587,8 +595,11 @@ mpc_dma_prep_memcpy(struct dma_chan *chan, dma_addr_t
> dst, dma_addr_t src,
> }
> spin_unlock_irqrestore(&mchan->lock, iflags);
>
> - if (!mdesc)
> + if (!mdesc) {
> + /* try to free completed descriptors */
> + mpc_dma_process_completed(mdma);
> return NULL;
> + }
>
> mdesc->error = 0;
> tcd = mdesc->tcd;
> --
> 1.7.2.3
>
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