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Date: Tue, 23 Aug 2011 10:40:05 +0200
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Greg KH <greg@kroah.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, "Hans J. Koch" <hjk@hansjkoch.de>,
        Chris Wright <chrisw@redhat.com>,
        Anthony Foiani <anthony.foiani@gmail.com>,
        Greg Kroah-Hartman <gregkh@suse.de>, linux-kernel@vger.kernel.org,
        Jesse Barnes <jbarnes@virtuousgeek.org>, stable@kernel.org
Subject: Re: [stable] [PATCH] uio/gen-pci: don't enable interrupts in ISR
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* Greg KH | 2011-08-22 17:49:43 [-0700]:

>> > Cc: Anthony Foiani <anthony.foiani@gmail.com>
>
>Why, it's not fixing a bug that anyone hits, right?

"earlier" the interrupt handler was executed either with interrupts
enabled or disabled if IRQF_DISABLED was specified. Later the latter
become default even if IRQF_DISABLED was not specified. This lead to the
splat Anthony reported because the irq handler was entered with IRQs
disabled and the ISR enabled them via spin_unlock_irq(). My initial
patch simply used spin_unlock_irqrestore() (and its counterpart) to have
the same state as we had.

So the bug Anthony hit was that the interrupts were enabled where they
should not be.

>greg k-h

Sebastian