linux-kernel - RE: [PATCH v2 2/2] x86: don't unmask disabled irqs when migrating them

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Message-ID: <alpine.DEB.2.00.1105061526120.10886@kaball-desktop>
Date:	Fri, 6 May 2011 15:28:38 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	"Tian, Kevin" <kevin.tian@...el.com>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>,
	Ian Campbell <Ian.Campbell@...citrix.com>,
	"JBeulich@...ell.com" <JBeulich@...ell.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>
Subject: RE: [PATCH v2 2/2] x86: don't unmask disabled irqs when migrating
 them

On Fri, 6 May 2011, Tian, Kevin wrote:
> > From: Thomas Gleixner
> > Sent: Friday, May 06, 2011 6:00 PM
> > 
> > On Fri, 6 May 2011, Tian, Kevin wrote:
> > > x86: don't unmask disabled irqs when migrating them
> > >
> > > it doesn't make sense to mask/unmask a disabled irq when migrating it
> > > from offlined cpu to another, because it's not expected to handle any
> > > instance of it. Current mask/set_affinity/unmask steps may trigger
> > > unexpected instance on disabled irq which then simply bug on when
> > > there is no handler for it. One failing example is observed in Xen.
> > > Xen pvops
> > 
> > So there is no handler, why the heck is there an irq action?
> > 
> > 	  if (!irq_has_action(irq) ....
> > 	     	continue;
> > 
> > Should have caught an uninitialized interrupt. If Xen abuses interrupts that way,
> > then it rightfully explodes. And we do not fix it by magic somewhere else.
> 
> sorry that my bad description here. there does be a dummy handler registered
> on such irqs which simply throws out a BUG_ON when hit. I should just say such 
> injection is not expected instead of no handler. :-)

I don't think this patch is necessary anymore after the event channel
handling cleanup patches I have just sent to the list.
Could you please try the following two patches:

http://marc.info/?l=linux-kernel&m=130468120032172&w=2
http://marc.info/?l=linux-kernel&m=130468178200468&w=2

and let me know if you still need this patch?
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