Re: [PATCH 2/2] i2c: i2c-omap: Call request_irq with IRQF_DISABLED

[Felipe Balbi <me@felipebalbi.com>]

On Wed, Mar 11, 2009 at 06:07:00PM -0600, Paul Walmsley wrote:
> Hi Felipe,
> 
> On Thu, 12 Mar 2009, Felipe Balbi wrote:
> 
> > On Wed, Mar 11, 2009 at 05:55:50PM -0600, Paul Walmsley wrote:
> > > Ben's right, there shouldn't be any need for this.  This patch could cause
> > > some unnecessary interrupt service latency.
> > 
> > That's not what Thomas Gleixner thinks. How about the possibility of
> > stack overflow ?
> 
> That sounds like a separate issue from the spurious IRQ problem that the 
> patch was intended to fix.   
> 
> I'm not familiar with the discussion on the stack overflow issue.  Could 
> you send a link?

This is the link where Ingo discusses why !IRQF_DISABLED could cause
stack overflow:

http://lkml.org/lkml/2009/3/3/71

You probably wanna take a look at the whole thread to figure out the
discussion, but basically Ingo and Peter (Zijlstra) believe
!IRQF_DISABLED is a bug and drivers needing that probably should be
using threaded irqs (which is not yet merged) or the hw is broken, and
for those an IRQF_ENABLED flag will be created and a TAINT will also be
placed.

Once that gets merged, all drivers will be forced (at some point) to
IRQF_DISABLED and those which don't want that will be moved gradually to
threaded irq.

This patch is also interesting:

http://lkml.org/lkml/2009/3/2/33

-- 
balbi