linux-kernel - Re: [PATCH 1/3] irq_work: Implement remote queueing

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Message-ID: <20140514091011.GI13658@twins.programming.kicks-ass.net>
Date:	Wed, 14 May 2014 11:10:11 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.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 1/3] irq_work: Implement remote queueing

On Wed, May 14, 2014 at 11:06:29AM +0200, Peter Zijlstra wrote:
> > +	llist_add(&work->llnode, &per_cpu(irq_work_list, cpu));
> > +	native_send_call_func_single_ipi(cpu);
> 
> At the very leastestest make that:
> 
> 	if (llist_add(&work->llnode, &per_cpu(irq_work_list, cpu)))
> 		native_send_call_func_single_ipi(cpu);
> 
> But ideally, also test the IRQ_WORK_LAZY support, its weird to have that
> only be supported for the other queue.
> 
> Hmm, why do we need that LAZY crap, that completely wrecks a perfectly
> simple thing.
> 
> The changelog (bc6679aef673f), not the printk() usage make much sense,

s/not/nor/

> printk() can't cause an IPI storm... printk() isn't fast enough to storm
> anything.

Except, as we all know, slow serial lines.

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