linux-kernel - Re: [PATCH v4 03/14] dmaengine: tegra-apb: Prevent race conditions on channel's freeing

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Date:   Tue, 14 Jan 2020 15:16:45 +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 03/14] dmaengine: tegra-apb: Prevent race conditions on
 channel's freeing


On 12/01/2020 17:29, Dmitry Osipenko wrote:
> It's incorrect to check the channel's "busy" state without taking a lock.
> That shouldn't cause any real troubles, nevertheless it's always better
> not to have any race conditions in the code.
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/dma/tegra20-apb-dma.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
> index 664e9c5df3ba..24ad3a5a04e3 100644
> --- a/drivers/dma/tegra20-apb-dma.c
> +++ b/drivers/dma/tegra20-apb-dma.c
> @@ -1294,8 +1294,7 @@ static void tegra_dma_free_chan_resources(struct dma_chan *dc)
>  
>  	dev_dbg(tdc2dev(tdc), "Freeing channel %d\n", tdc->id);
>  
> -	if (tdc->busy)
> -		tegra_dma_terminate_all(dc);
> +	tegra_dma_terminate_all(dc);
>  
>  	spin_lock_irqsave(&tdc->lock, flags);
>  	list_splice_init(&tdc->pending_sg_req, &sg_req_list);

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

Cheers
Jon

-- 
nvpublic