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

[Alan Stern <stern@rowland.harvard.edu>]

[Most people removed from CC: since they probably aren't too interested in 
this.]

On Mon, 2 Oct 2006, David Brownell wrote:

> 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.

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

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.

Alan Stern

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