linux-kernel - Re: [PATCH RT] ehea: make receive irq handler non-threaded (IRQF

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Date:	Thu, 20 May 2010 11:34:08 +1000
From:	Michael Ellerman <michael@...erman.id.au>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Darren Hart <dvhltc@...ibm.com>,
	Brian King <brking@...ux.vnet.ibm.com>,
	Jan-Bernd Themann <themann@...ibm.com>,
	dvhltc@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	Will Schmidt <will_schmidt@...t.ibm.com>,
	niv@...ux.vnet.ibm.com, Doug Maxey <doug.maxey@...ibm.com>,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH RT] ehea: make receive irq handler non-threaded
 (IRQF_NODELAY)

On Wed, 2010-05-19 at 23:08 +0200, Thomas Gleixner wrote:
> On Wed, 19 May 2010, Thomas Gleixner wrote:
> > > I'm still not clear on why the ultimate solution wasn't to have XICS report
> > > edge triggered as edge triggered. Probably some complexity of the entire power
> > > stack that I am ignorant of.
> > > 
> > > > Apart from the issue of loosing interrupts there is also the fact that
> > > > masking on the XICS requires an RTAS call which takes a global lock.
> > 
> > Right, I'd love to avoid that but with real level interrupts we'd run
> > into an interrupt storm. Though another solution would be to issue the
> > EOI after the threaded handler finished, that'd work as well, but
> > needs testing.
> 
> Thought more about that. The case at hand (ehea) is nasty:
> 
> The driver does _NOT_ disable the rx interrupt in the card in the rx
> interrupt handler - for whatever reason.

Yeah I saw that, but I don't know why it's written that way. Perhaps
Jan-Bernd or Doug will chime in and enlighten us? :)

cheers



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