linux-kernel - Re: [PATCH 3/3] IRQ: Maintain regs pointer globally rather than passing to IRQ handlers

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Message-Id: <200610021600.24477.david-b@pacbell.net>
Date:	Mon, 2 Oct 2006 16:00:22 -0700
From:	David Brownell <david-b@...bell.net>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Andrew Morton <akpm@...l.org>, David Howells <dhowells@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, torvalds@...l.org,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	Dmitry Torokhov <dtor@...l.ru>, Greg KH <greg@...ah.com>
Subject: Re: [PATCH 3/3] IRQ: Maintain regs pointer globally rather than passing to IRQ handlers

On Monday 02 October 2006 2:34 pm, Alan Stern wrote:
> On Mon, 2 Oct 2006, David Brownell wrote:
> 
> > > >  (*) finish_unlinks() in drivers/usb/host/ohci-q.c needs checking.  It does
> > > >      something different depending on whether it's been supplied with a regs
> > > >      pointer or not.
> > 
> > gaak!  where did that come from?  I'll be surprised if removing
> > that causes any problem at all.
> 
> Here's the statement in question:
> 
> 	if (likely (regs && HC_IS_RUNNING(ohci_to_hcd(ohci)->state))) {

Where as I said, removing the "regs &&" should be just fine.
(Is the plan that David Howells re-issue that patch?  If so, I'l
expect e will just fix it that way...)

> 		...
> 
> Notice another questionable use of hcd->state. 

Questionable in what way?  When that code is called to clean up
after driver death, that loop must be ignored ... every pending I/O
can safely be scrubbed.  That's the main point of that particular
HC_IS_RUNNING() test.  In other cases, it's essential not to touch
DMA queue entries that the host controller is still using.

- Dave

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