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

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Message-ID: <1331b7c1-3839-69cb-4de2-16771c652d41@nvidia.com>
Date:   Tue, 14 Jan 2020 15:43:35 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Vinod Koul <vkoul@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>
CC:     <dmaengine@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 05/14] dmaengine: tegra-apb: Prevent race conditions of
 tasklet vs free list


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@...il.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@...dia.com>

Cheers
Jon

-- 
nvpublic