linux-kernel - Re: [PATCH] prevent sparc64 from invoking irq handlers on offline CPUs

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Date:	Tue, 09 Sep 2008 12:57:14 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	manfred@...orfullife.com
Cc:	paulmck@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	wli@...omorphy.com, sparclinux@...r.kernel.org,
	akpm@...ux-foundation.org
Subject: Re: [PATCH] prevent sparc64 from invoking irq handlers on offline
 CPUs

From: Manfred Spraul <manfred@...orfullife.com>
Date: Tue, 09 Sep 2008 20:49:04 +0200

> David Miller wrote:
> > And IPI handler runs in HW irq context, therefore such an IPI-creates-an-IPI
> > should not be allowed, at least not directly.
> >
> > Actually the restriction seems to be that an IPI cannot be sent when
> > "irqs_disabled()", hmmm...
> >
> >   
> Does this apply to smp_send_reschedule() as well?
> A [rare] codepath in the current rcu code does to trigger quiescent states on remote cpus.

It does work on sparc64.  Such an IPI doesn't do a wait so there would
be no deadlock issues either.

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