linux-kernel - Re: [stable] [PATCH] uio/gen-pci: don't enable interrupts in ISR

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Message-ID: <20110823084005.GB20979@linutronix.de>
Date:	Tue, 23 Aug 2011 10:40:05 +0200
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Greg KH <greg@...ah.com>
Cc:	"Michael S. Tsirkin" <mst@...hat.com>,
	"Hans J. Koch" <hjk@...sjkoch.de>,
	Chris Wright <chrisw@...hat.com>,
	Anthony Foiani <anthony.foiani@...il.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	linux-kernel@...r.kernel.org,
	Jesse Barnes <jbarnes@...tuousgeek.org>, stable@...nel.org
Subject: Re: [stable] [PATCH] uio/gen-pci: don't enable interrupts in ISR

* Greg KH | 2011-08-22 17:49:43 [-0700]:

>> > Cc: Anthony Foiani <anthony.foiani@...il.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
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