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Date: Thu, 25 Feb 2016 15:06:54 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Vineet Gupta <Vineet.Gupta1@synopsys.com>
Cc: Russell King <linux@arm.linux.org.uk>,
        "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        lkml <linux-kernel@vger.kernel.org>, Noam Camus <noamc@ezchip.com>,
        arcml <linux-snps-arc@lists.infradead.org>
Subject: Re: Interesting csd deadlock on ARC
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On Wed, Feb 24, 2016 at 10:21:25AM +0530, Vineet Gupta wrote:
> >> What I actually meant was is it OK for irq_work_queue_on() to be called locally
> >> (is this a sched bug/optimization(. Further if it is OK to be called, does it need
> >> to do behave more like irq_work_queue() i.e. call arch_irq_work_raise() or
> >> arch_send_call_function_single_ipi() is expected to handle sending IPI to self !
> > 
> > Right, so I'm not actually sure we started out with this requirement.
> > But you're not the first to run into this, see:
> > 
> >   lkml.kernel.org/r/CAJZ5v0gLankSuziQq25qTCyNqeOX43yD9jnJu_XXwbdyajfmKg@mail.gmail.com
> > 
> > Initially I think irq_work_queue_on() was only used remotely, but I
> > think it makes sense to allow the current cpu, esp. since people seem to
> > be using it like that.
> 
> So it seems Russell's questions in the thread above stands still. IMO we need to
> massage irq_work_queue_on() to handle the case of called for local cpu. This will
> automatically take care of CONFIG_SMP kernel running on UP hardware.

Hmm, I missed that there was still an open question.

Afaict the only thing that needs doing to the generic code is drop the
CONFIG_SMP guard, no?