Re: [PATCH v4 05/14] dmaengine: tegra-apb: Prevent race conditions of tasklet vs free list

Jon Hunter
2020-01-14T15:43:41Z

On 12/01/2020 17:29, Dmitry Osipenko wrote:
> The interrupt handler puts a half-completed DMA descriptor on a free list
> and then schedules tasklet to process bottom half of the descriptor that
> executes client's callback, this creates possibility to pick up the busy
> descriptor from the free list. Thus let's disallow descriptor's re-use
> until it is fully processed.
>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
> drivers/dma/tegra20-apb-dma.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
> index 1b8a11804962..aafad50d075e 100644
> --- a/drivers/dma/tegra20-apb-dma.c
> +++ b/drivers/dma/tegra20-apb-dma.c
> @@ -281,7 +281,7 @@ static struct tegra_dma_desc *tegra_dma_desc_get(
>
> /* Do not allocate if desc are waiting for ack */
> list_for_each_entry(dma_desc, &tdc->free_dma_desc, node) {
> - if (async_tx_test_ack(&dma_desc->txd)) {
> + if (async_tx_test_ack(&dma_desc->txd) && !dma_desc->cb_count) {
> list_del(&dma_desc->node);
> spin_unlock_irqrestore(&tdc->lock, flags);
> dma_desc->txd.flags = 0;
>

Acked-by: Jon Hunter <jonathanh@nvidia.com>

Cheers
Jon

--
nvpublic