linux-kernel - Re: [PATCH v2] dma: Add Xilinx AXI Video Direct Memory Access Engine driver support

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Message-ID: <1390484317.7619.81.camel@smile>
Date:	Thu, 23 Jan 2014 13:38:37 +0000
From:	"Shevchenko, Andriy" <andriy.shevchenko@...el.com>
To:	Lars-Peter Clausen <lars@...afoo.de>
CC:	Srikanth Thokala <sthokal@...inx.com>,
	"Williams, Dan J" <dan.j.williams@...el.com>,
	"Koul, Vinod" <vinod.koul@...el.com>,
	"michal.simek@...inx.com" <michal.simek@...inx.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>
Subject: Re: [PATCH v2] dma: Add Xilinx AXI Video Direct Memory Access
 Engine driver support

On Thu, 2014-01-23 at 12:25 +0100, Lars-Peter Clausen wrote:
> On 01/22/2014 05:52 PM, Srikanth Thokala wrote:

[...]

> > +	/* Request the interrupt */
> > +	chan->irq = irq_of_parse_and_map(node, 0);
> > +	err = devm_request_irq(xdev->dev, chan->irq, xilinx_vdma_irq_handler,
> > +			       IRQF_SHARED, "xilinx-vdma-controller", chan);
> 
> This is a clasic example of where to not use devm_request_irq. 'chan' is
> accessed in the interrupt handler, but if you use devm_request_irq 'chan'
> will be freed before the interrupt handler has been released, which means
> there is now a race condition where the interrupt handler can access already
> freed memory.

Could you elaborate this case? As far as I understood managed resources
are a kind of stack pile. In this case you have no such condition. Where
am I wrong?


-- 
Andy Shevchenko <andriy.shevchenko@...el.com>
Intel Finland Oy
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