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Date: Wed, 18 Dec 2013 16:58:10 +0100
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        John Stultz <john.stultz@linaro.org>, Alex Shi <alex.shi@linaro.org>,
        Kevin Hilman <khilman@linaro.org>
Subject: Re: [PATCH 05/13] rcu: Fix unraised IPI to timekeeping CPU
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On Wed, Dec 18, 2013 at 04:11:58PM +0100, Peter Zijlstra wrote:
> On Wed, Dec 18, 2013 at 03:56:12PM +0100, Frederic Weisbecker wrote:
> > Because scheduler_ipi() conditionally calls irq_enter() and irq_exit()
> > (I wonder if that's a good idea btw, is that here to deal with spurious
> > scheduler IPIs of some sort?)
> 
> No its because the traditional scheduler IPI did all the work from the
> interrupt return path -- and like the comment in there says, for many of
> the IPIs that's still true.
> 
> So going through the architectures and making all scheduler_ipi callers
> do irq_enter/exit would actually make them slower.

Fair point!

Thanks.