linux-kernel - RE: [PATCH] DMA: Fix broken device refcounting

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Message-ID: <BAE9DCEF64577A439B3A37F36F9B691C034CC702@orsmsx418.amr.corp.intel.com>
Date:	Fri, 26 Oct 2007 10:10:17 -0700
From:	"Nelson, Shannon" <shannon.nelson@...el.com>
To:	"Nelson, Shannon" <shannon.nelson@...el.com>,
	"Haavard Skinnemoen" <hskinnemoen@...el.com>
Cc:	"Williams, Dan J" <dan.j.williams@...el.com>,
	<linux-kernel@...r.kernel.org>, <akpm@...ux-foundation.org>
Subject: RE: [PATCH] DMA: Fix broken device refcounting

>-----Original Message-----
>From: Nelson, Shannon 
>Sent: Friday, October 26, 2007 10:00 AM
>To: 'Haavard Skinnemoen'
>Cc: Williams, Dan J; linux-kernel@...r.kernel.org; 
>akpm@...ux-foundation.org
>Subject: RE: [PATCH] DMA: Fix broken device refcounting
>
>--
>
>When a channel is removed from dmaengine, too many kref_put() calls
>are made and the device removal happens too soon, usually causing
>a panic.
>
>Signed-off-by: Shannon Nelson <shannon.nelson@...el.com>
>---
>
> drivers/dma/dmaengine.c |    1 -
> 1 files changed, 0 insertions(+), 1 deletions(-)
>
>diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
>index 8248992..144a1b7 100644
>--- a/drivers/dma/dmaengine.c
>+++ b/drivers/dma/dmaengine.c
>@@ -131,7 +131,6 @@ static void 
>dma_async_device_cleanup(struct kref *kref);
> static void dma_class_dev_release(struct class_device *cd)
> {
> 	struct dma_chan *chan = container_of(cd, struct 
>dma_chan, class_dev);
>-	kref_put(&chan->device->refcount, dma_async_device_cleanup);
> }
> 
> static struct class dma_devclass = {

Of course, to avoid compiler complaints, it might be better as something
like:

static void dma_class_dev_release(struct class_device *cd)
{
-	struct dma_chan *chan = container_of(cd, struct dma_chan,
class_dev);
-	kref_put(&chan->device->refcount, dma_async_device_cleanup);
+	return;
}

sln
-
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