linux-kernel - Re: [git patch] free

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Message-ID: <481066C1.1030805@garzik.org>
Date:	Thu, 24 Apr 2008 06:53:53 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Rene Herman <rene.herman@...access.nl>,
	Adrian Bunk <bunk@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, rmk@....linux.org.uk,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [git patch] free_irq() fixes

Eric W. Biederman wrote:
> I haven't looked at what Jeff's patches in particular so I can not
> comment there.  I do remember looking at the drivers in question and
> yes there were indeed bugs with the handful of drivers that used
> the irq parameter.  So fixing and cleaning up those drivers so they
> use the same idioms as the rest of the kernel should be a maintenance
> win.  Even if we do keep the irq parameter to the interrupt handler.
> 
> I can comment on where there seems to be a real need for change.
> The hard coded NR_IRQS parameter and the arrays of size NR_IRQS are a
> kernel scaling bottle neck.  They prevents us from building one kernel
> that works well on a large ranges of machines sizes.  Having a single
> array prevents us from allocating the irq structures with NUMA
> affinity which slows down irq processing.  Having a small number for
> NR_IRQS to keep the table compact keeps the irq number from being
> readable/useful in the case of MSI and occasionally in the case of
> IO_APICs.


Honestly, one thing I was thinking was perhaps a change from

	irqreturn_t foo_handler(int irq, void *dev_id)
to
	irqreturn_t foo_handler(struct irq_info *ii, void *dev_id)

which would IMO make the first parameter useful again, by enabling 
passing of information like MSI message info, or more flexible 
platform-specific irq info that a platform driver may want.  Or direct 
access to irq_desc or irq_chip info.

	Jeff



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