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Re: oops in futex_init()

To: Manuel Lauss <mano@roarinelk.homelinux.net>
Subject: Re: oops in futex_init()
From: Ralf Baechle <ralf@linux-mips.org>
Date: Wed, 29 Apr 2009 16:35:23 +0200
Cc: Linux-MIPS <linux-mips@linux-mips.org>
In-reply-to: <20090429141411.GA25905@roarinelk.homelinux.net>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20090428124645.GA14347@roarinelk.homelinux.net> <20090429060317.GB15627@linux-mips.org> <20090429082556.GA22844@roarinelk.homelinux.net> <20090429083349.GB26289@linux-mips.org> <20090429114042.GA24576@roarinelk.homelinux.net> <20090429141411.GA25905@roarinelk.homelinux.net>
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On Wed, Apr 29, 2009 at 04:14:11PM +0200, Manuel Lauss wrote:

> FWIW, I think I fixed it: I have a small area (< 4kB) with a lot of UARTs
> and 3 interrupt controllers in it.  An ioremap() was done for each uart and
> irq ctl area.  Now there's one ioremap of the whole area and the oops is
> gone.  I don't know why, but it seems fixed. (The oops appeared after one
> of the remapped areas was touched).

That should be benign - especially if the mappings are for physical
addresses < 512MB which would become mapped as KSEG1 addresses.  The
dangerous cases are where multiple mappings alias (can't happen on
Alchemy caches) or where different machines use different cache modes
which also shouldn't hit you because I/O addresses should be mapped
uncachable.  So you may want to try out what Kevin suggested to get to
the root of this.

  Ralf

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