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

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Message-ID: <625BA99ED14B2D499DC4E29D8138F1505C8ED7F99D@shsmsx502.ccr.corp.intel.com>
Date:	Sat, 7 May 2011 05:43:12 +0800
From:	"Tian, Kevin" <kevin.tian@...el.com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.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

> From: Stefano Stabellini [mailto:stefano.stabellini@...citrix.com]
> Sent: Friday, May 06, 2011 10:29 PM
> 
> 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?

thanks, and I'll take a look at them.

Thanks
Kevin
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