linux-kernel - Re: [PATCH 6/6] dmaengine: tegra-apb: Disable interrupts on removal

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Message-ID: <20151028065339.GE3041@vkoul-mobl.iind.intel.com>
Date:	Wed, 28 Oct 2015 15:53:41 +0900
From:	Vinod Koul <vinod.koul@...el.com>
To:	Jon Hunter <jonathanh@...dia.com>
Cc:	Lars-Peter Clausen <lars@...afoo.de>,
	Laxman Dewangan <ldewangan@...dia.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Courbot <gnurou@...il.com>,
	dmaengine@...r.kernel.org, linux-tegra@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/6] dmaengine: tegra-apb: Disable interrupts on removal

On Fri, Oct 16, 2015 at 11:57:02AM +0100, Jon Hunter wrote:
> >>> How about just calling free_irq()? That's how you'd typically handle this.
> >>
> >> Yes, however, the interrupt is requested by devm_request_irq(). I guess
> >> I could call devm_free_irq() here?
> > 
> > Just use request_irq() instead of devm_request_irq(). You have the same
> > issue on the error path in the probe function anyway and also need to add
> > the free_irq() before the tasklet_kill() there as well.
> 
> I was wondering about that but the tasklets should never be scheduled if
> the probe does not succeed, so I think it is ok.

This is actually very racy, if probe fails but due to devm_ calls your irq
is alive till it freed by core

And a faulty device triggering irq can complicate matters, so for irq IMHO
we don't get much benefit with devm_ variant

-- 
~Vinod
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