Re: Dangerous devm_request_irq() conversions

From: Jingoo Han
Date: Fri Feb 22 2013 - 02:12:45 EST

On Friday, February 22, 2013 3:54 PM, Dmitry Torokhov wrote:
> Hi,
> It looks like a whole slew of devm_request_irq() conversions just got
> applied to mainline and many of them are quite broken.
> Consider fd5231ce336e038037b4f0190a6838bdd6e17c6d or
> c1879fe80c61f3be6f2ddb82509c2e7f92a484fe: the drivers udsed first to
> free IRQ and then unregister the corresponding device ensuring that IRQ
> handler, while it runs, has the device available. The mechanic
> conversion to devm_request_irq() reverses the order of these operations
> opening the race window where IRQ can reference device (or other
> resource) that is already gone.
> It would be nice if these could be reverted and revioewed again for
> correctness.

Um, other RTC drivers already have been using devm_request_threaded_irq() or
devm_request_irq() like this, before I added these patches.

For example,

Also, even more, some RTC drivers calls rtc_device_unregister() first,
then calls free_irq() later.

For example,

Please, don't argue revert without concrete reasons.

If these devm_request_threaded_irq() or devm_request_irq() make the problem,
devm_free_irq() will be added later.

> In general any conversion to devm_request_irq() needs double and triple
> checking.
> Thanks.
> --
> Dmitry

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