Date: Mon, 12 Nov 2012 17:17:12 -0800
From: Josh Triplett <josh@joshtriplett.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org,
        linux-rt-users@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com,
        dipankar@in.ibm.com, akpm@linux-foundation.org,
        mathieu.desnoyers@efficios.com, niv@us.ibm.com, tglx@linutronix.de,
        peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu,
        dhowells@redhat.com, edumazet@google.com, darren@dvhart.com,
        sbw@mit.edu, patches@linaro.org
Subject: Re: Does anyone use CONFIG_TINY_PREEMPT_RCU?
Message-ID: <20121113011712.GA20884@jtriplet-mobl1>
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On Tue, Nov 13, 2012 at 02:12:27AM +0100, Frederic Weisbecker wrote:
> 2012/11/13 Paul E. McKenney <paulmck@linux.vnet.ibm.com>:
> > Hello!
> >
> > I know of people using TINY_RCU, TREE_RCU, and TREE_PREEMPT_RCU, but I
> > have not heard of anyone using TINY_PREEMPT_RCU for whom TREE_PREEMPT_RCU
> > was not a viable option (in contrast, the people running Linux on
> > tiny-memmory systems typically use TINY_RCU).  Of course, if no one
> > really needs it, the proper thing to do is to remove it.
> >
> > So, if you need TINY_PREEMPT_RCU, please let me know.  Otherwise, I will
> > remove it, probably in the 3.9 timeframe.
> 
> I don't use it personally but if you remove it, does that mean that
> RCU couldn't be preemptible on UP?

No, it would mean that on UP you could choose between TINY_RCU and
TREE_PREEMPT_RCU, depending on whether you want tiny or preemptible.

- Josh Triplett
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