linux-kernel - Re: [PATCH] dmatest: properly handle duplicate DMA channels

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Date:	Fri, 19 Sep 2008 16:31:45 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Timur Tabi <timur@...escale.com>
Cc:	dan.j.williams@...el.com, haavard.skinnemoen@...el.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmatest: properly handle duplicate DMA channels

On Thu, 18 Sep 2008 10:21:19 -0500
Timur Tabi <timur@...escale.com> wrote:

> --- a/drivers/dma/dmatest.c
> +++ b/drivers/dma/dmatest.c
> @@ -321,10 +321,15 @@ static void dmatest_cleanup_channel(struct dmatest_chan *dtc)
>  
>  static enum dma_state_client dmatest_add_channel(struct dma_chan *chan)
>  {
> -	struct dmatest_chan	*dtc;
> +	struct dmatest_chan	*dtc, *_dtc;
>  	struct dmatest_thread	*thread;
>  	unsigned int		i;
>  
> +	/* Have we already been told about this channel? */
> +	list_for_each_entry_safe(dtc, _dtc, &dmatest_channels, node)
> +		if (dtc->chan == chan)
> +			return DMA_DUP;
> +
>  	dtc = kmalloc(sizeof(struct dmatest_chan), GFP_ATOMIC);
>  	if (!dtc) {
>  		pr_warning("dmatest: No memory for %s\n", chan->dev.bus_id);

hm.  A few lines after that GFP_ATOMIC the driver does a GFP_KERNEL
allocation.

One of them is incorrect.  The interface is undocumented (natch), but I
assume that GFP_KERNEL is the one to use here.

--- a/drivers/dma/dmatest.c~a
+++ a/drivers/dma/dmatest.c
@@ -330,7 +330,7 @@ static enum dma_state_client dmatest_add
 		if (dtc->chan == chan)
 			return DMA_DUP;
 
-	dtc = kmalloc(sizeof(struct dmatest_chan), GFP_ATOMIC);
+	dtc = kmalloc(sizeof(struct dmatest_chan), GFP_KERNEL);
 	if (!dtc) {
 		pr_warning("dmatest: No memory for %s\n", chan->dev.bus_id);
 		return DMA_NAK;
_

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