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Date: Thu, 5 Oct 2017 10:37:59 -0500
From: Julia Cartwright <julia@ni.com>
To: Thomas Gleixner <tglx@linutronix.de>
CC: Arnaldo Carvalho de Melo <acme@kernel.org>, <bigeasy@linutronix.de>,
        <linux-rt-users@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
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        Sebastian Andrzej Siewior <sebastian.siewior@linutronix.de>,
        Sebastian Sanchez <sebastian.sanchez@intel.com>,
        Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 1/2] IB/hfi1: Use preempt_{dis,en}able_nort()
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On Thu, Oct 05, 2017 at 05:27:30PM +0200, Thomas Gleixner wrote:
> On Thu, 5 Oct 2017, Julia Cartwright wrote:
> > On Tue, Oct 03, 2017 at 12:49:19PM -0300, Arnaldo Carvalho de Melo wrote:
> > > -	preempt_disable();
> > > +	preempt_disable_nort();
> > >  	this_cpu_inc(*sc->buffers_allocated);
> > 
> > Have you tried this on RT w/ CONFIG_DEBUG_PREEMPT?  I believe that the
> > this_cpu_* operations perform a preemption check, which we'd trip.
> 
> Good point. Changing this to migrate_disable() would do the trick.

Wouldn't we still trip the preempt check even with migration disabled?
In another thread I asked the same question: should the preemption
checks here be converted to migration-checks in RT?

   Julia