linux-kernel - Re: pull request: wireless 2011-11-22

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Message-ID: <20111122205655.GE8452@tuxdriver.com>
Date:	Tue, 22 Nov 2011 15:56:55 -0500
From:	"John W. Linville" <linville@...driver.com>
To:	David Miller <davem@...emloft.net>
Cc:	linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: pull request: wireless 2011-11-22

On Tue, Nov 22, 2011 at 03:14:29PM -0500, David Miller wrote:
> From: "John W. Linville" <linville@...driver.com>
> Date: Tue, 22 Nov 2011 14:35:05 -0500
> 
> > Here is the latest batch of fixes intended for 3.2.  This includes a
> > correction for a user-visible error in mac80211's debugfs info, a fix
> > for a potential memory corrupter in prism54, an endian fix for rt2x00,
> > an endian fix for mac80211, a fix for a NULL derefernce in cfg80211, a
> > locking fix and a deadlock fix for p54spi, and a pair of rt2x00 fixes
> > for handling some spurious interrupts that hardware can generate.
> > 
> > Please let me know if there are problems!
> 
> The rt2800pci change doesn't look correct.
> 
> If the IRQ line is shared with another device, this change will make it
> never see interrupts.  Once you say "IRQ_HANDLED" the IRQ dispatch
> stops processing the interrupt handler list.

I thought this at first as well.  But looking at the code in
kernel/irq/handle.c doesn't support that conclusion.  In fact, every
handler gets invoked no matter what they all return.  All of the irq
handler return values are ORed together and passed to note_interrupt.
Only if every irq handler returns IRQ_NONE does the code in
kernel/irq/spurious.c start getting involved.

Anyway, this seems to be safe even for shared interrupts.  That said,
this is a bit ugly.  But it makes a serious difference in performance
for those afflicted with this issue.

John
-- 
John W. Linville		Someday the world will need a hero, and you
linville@...driver.com			might be all we have.  Be ready.
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