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

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Message-Id: <200610052045.41211.david-b@pacbell.net>
Date:	Thu, 5 Oct 2006 20:45:40 -0700
From:	David Brownell <david-b@...bell.net>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] IRQ: Maintain regs pointer globally rather than passing to IRQ handlers

On Tuesday 03 October 2006 11:03 am, Alan Stern wrote:

> > > 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.
> 
> Questionable because changes to hcd->state aren't synchronized with the
> driver.  In this case it probably doesn't end up making any difference.

The driver changes hcd->state with its spinlock held ... or it did,
last time I audited that code.


> Removing "regs &&" might change other aspects too.  For instance, does 
> this routine ever get called from a timer routine, where regs would 
> normally be NULL?  In such situations removing "regs &&" would reverse 
> the sense of the test.

As I said in my previous comments:  should not be an issue.  OHCI doesn't
have timers.  That routine is normally called in_irq(), with the other
two call sites being cases where the controller is stopped.

- Dave
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