linux-kernel - Re: [PATCH 3/5] irq_work: Implement remote queueing

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Message-ID: <1401825759.3645.233.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 03 Jun 2014 13:02:39 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kevin Hilman <khilman@...aro.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: Re: [PATCH 3/5] irq_work: Implement remote queueing

On Tue, 2014-06-03 at 18:37 +0200, Peter Zijlstra wrote:
> On Tue, Jun 03, 2014 at 09:29:07AM -0700, Eric Dumazet wrote:
> > > +bool irq_work_queue_on(struct irq_work *work, int cpu)
> > > +{
> > > +	/* All work should have been flushed before going offline */
> > > +	WARN_ON_ONCE(cpu_is_offline(cpu));
> > > +
> > > +	/* Arch remote IPI send/receive backend aren't NMI safe */
> > > +	WARN_ON_ONCE(in_nmi());
> > > +
> > > +	/* Only queue if not already pending */
> > > +	if (!irq_work_claim(work))
> > > +		return false;
> > > +
> > > +	if (llist_add(&work->llnode, &per_cpu(raised_list, cpu)))
> > > +		native_send_call_func_single_ipi(cpu);
> > > +
> > > +	return true;
> > > +}
> > > +EXPORT_SYMBOL_GPL(irq_work_queue_on);
> > > +
> > 
> > I am curious, this should only compile on x86, right ?
> 
> Oh, you tease, you forgot to say why you think this.
> 
> Are you referring to the in_nmi() usage? that's from
> include/linux/hardirq.h, hardly x86 specific.

No, my eyes were attracted by native_send_call_func_single_ipi()




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