linux-kernel - Re: [PATCH] rcu: Is it safe to enter an RCU read-side critical section?

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Date:	Mon, 9 Sep 2013 14:49:42 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...icios.com, josh@...htriplett.org,
	niv@...ibm.com, tglx@...utronix.de, rostedt@...dmis.org,
	dhowells@...hat.com, edumazet@...gle.com, darren@...art.com,
	sbw@....edu
Subject: Re: [PATCH] rcu: Is it safe to enter an RCU read-side critical
 section?

On Mon, 9 Sep 2013, Peter Zijlstra wrote:

> On Mon, Sep 09, 2013 at 06:23:43AM -0700, Paul E. McKenney wrote:
> > And guys, I have to say that the advice on which per-CPU primitive to use
> > varies wildly and randomly.  For all I know, each of you individually
> > might well be sticking to the same story, but taken together, your
> > collective advice is strongly resembling white noise.
>
> Its partly because cl and I disagree on things. He doesn't seem to care
> much about validation and believes that people will not make mistakes
> with this stuff.

Slander. Certainly validation is good. Its just that PREEMPT kernels are
not in use and AFAICT the full preempt stuff requires significant developer
support and complicates the code without much benefit.

Having said that I am trying to support preeempt checks. The newest
__get_cpu_var patchset introduces the preempt checks that you want.
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