After being bitten by unsafe usage of disable_irq from within that irq's
handler [1], I went through and used Coccinelle to audit the rest of
drivers/ too.  This turned up 9 more unsafe usages.

As Haavard pointed out in that thread, disable_irq waits for running
handlers of an irq to complete before returning.  When a handler
disable_irq's its own irq then we see a deadlock.

Note that this wasn't actually observed in the wild until the recent
merge of

commit 3aa551c9b4c40018f0e261a178e3d25478dc04a9
Author: Thomas Gleixner <tglx@linutronix.de>
Date:   Mon Mar 23 18:28:15 2009 +0100

    genirq: add threaded interrupt handler support

    Add support for threaded interrupt handlers



Regards,
	--Ben.


[1] http://lkml.org/lkml/2009/4/15/498

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