linux-kernel - Re: [patch 2.6.28-rc2] at91

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Date:	Mon, 03 Nov 2008 14:47:33 +0100
From:	Nicolas Ferre <nicolas.ferre@...el.com>
To:	David Brownell <david-b@...bell.net>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Pierre Ossman <drzeus-mmc@...eus.cx>,
	lkml <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Russell King <rmk@....linux.org.uk>,
	Nicolas Ferre <nicolas.ferre@....atmel.com>,
	Andrew Victor <linux@...im.org.za>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 2.6.28-rc2] at91_mci: workaround lockdep

David Brownell :
> On Tuesday 28 October 2008, Peter Zijlstra wrote:
>> On Mon, 2008-10-27 at 14:26 -0700, David Brownell wrote:
>>> From: David Brownell <dbrownell@...rs.sourceforge.net>
>>>
>>> Lockdep reported a problem in the at91_mci driver ... in this case, the
>>> issue is with lockdep, not with the driver. ...
>>>
>>> When __flush_dcache_aliases() returns -- inlined into flush_dcache_page(),
>>> above -- it re-enables IRQs ... since that evidently may only be called with
>>> IRQs enabled.  That's OK since the (unshared) IRQ handler doesn't ask for IRQs
>>> to be disabled.   Except ... that lockdep went and disabled them, then went on
>>> to complains about the breakage *it* caused!
>>>
>>> Workaround: depend on LOCKDEP=n ... 
>> In all previous such cases it was deemed the IRQ handler should deal
>> with whatever it gets.
> 
> In which case I'll wait until someone changes that IRQ handler (or that
> ARM MM utility, or lockdep), and give up using AT91 platforms for sanity
> testing kernel changes; lockdep is important, when it doesn't lie.

Changing IRQ handler in this driver... seem to be a big work.

Well, Dave, I tend to acknowledge your patch above as the IRQ for MCI is 
indeed a dedicated line (no need for IRQF_SHARED).

Are you ok with this ?

Regards,
-- 
Nicolas Ferre

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