From: "Paul E. McKenney" <paulmck@us.ibm.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: dipankar@in.ibm.com, shemminger@osdl.org, akpm@osdl.org,
torvalds@osdl.org, rusty@au1.ibm.com, tgall@us.ibm.com,
jim.houston@comcast.net, manfred@colorfullife.com, gh@us.ibm.com,
linux-kernel@vger.kernel.org
Subject: Re: Real-Time Preemption and RCU
Date: Fri, 18 Mar 2005 09:29:23 -0800 [thread overview]
Message-ID: <20050318172923.GI1299@us.ibm.com> (raw)
In-Reply-To: <20050318171126.GA30310@elte.hu>
On Fri, Mar 18, 2005 at 06:11:26PM +0100, Ingo Molnar wrote:
>
> * Paul E. McKenney <paulmck@us.ibm.com> wrote:
>
> > For the patch, here are my questions:
> >
> > o What is the best way to select between classic RCU and this
> > scheme?
> >
> > 1. Massive #ifdef across rcupdate.c
> >
> > 2. Create an rcupdate_rt.c and browbeat the build system
> > into picking one or the other (no clue if this is
> > possible...)
> >
> > 3. Create an rcupdate_rt.c and rely on the linker to pick
> > one or the other, with rcupdate.h generating different
> > external symbol names to make the choice.
>
> you can also go for option #0: just replace the existing RCU code with
> the new one, and i'll then deal with the configuration details.
Having just spent the past few minutes descending into #ifdef hell,
I agree completely with your option #0.
> what will have to happen is most likely #2 (since there is near zero
> code sharing between the two variants, right?). Picking rcupdate_rt.c is
> as simple as doing this:
>
> obj-$(CONFIG_DONT_PREEMPT_RCU) += rcupdate.o
> obj-$(CONFIG_PREEMPT_RCU) += rcupdate_rt.o
>
> and then use Kconfig to generate either CONFIG_DONT_PREEMPT_RCU
> (default) or CONFIG_PREEMPT_RCU (if the user selects it).
Cool! Thank you for the tutorial! And yes, there is no shared code
that I can see.
> but it's not yet clear whether we want to offer this to users as a
> configurable option. The simplest solution for you would be to go with
> option #0 :-) [or if you prefer switchability, #1 is good too - i can
> then extract the bits and do #2 based on that.]
Option #0 it is -- I will stick with the locking algorithms and let
wiser and more experienced heads work out the configuration issues.
> > o How best to interface to OOM? Left to myself, I leave this
> > for later. ;-)
>
> yeah, i'd not worry about OOM that much at this stage.
>
> > I will take the cowardly approach of patching against the upstream
> > kernel.
>
> sure. This is in fact easier for me: i'll first rip all my RCU hackery
> out of -RT and then add your code, so the base i'll be merging against
> will be closer to upstream than to current -RT.
Sounds good to me!
Thanx, Paul
next prev parent reply other threads:[~2005-03-18 17:29 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-03-18 0:20 Real-Time Preemption and RCU Paul E. McKenney
2005-03-18 7:49 ` Ingo Molnar
2005-03-18 16:43 ` Paul E. McKenney
2005-03-18 17:11 ` Ingo Molnar
2005-03-18 17:29 ` Paul E. McKenney [this message]
2005-03-18 20:35 ` Paul E. McKenney
2005-03-18 22:22 ` Paul E. McKenney
2005-03-19 0:48 ` Paul E. McKenney
2005-03-18 8:44 ` Ingo Molnar
2005-03-18 9:04 ` Ingo Molnar
2005-03-18 9:38 ` Ingo Molnar
2005-03-18 9:13 ` Ingo Molnar
2005-03-18 9:28 ` Ingo Molnar
2005-03-18 9:53 ` Ingo Molnar
2005-03-18 15:33 ` Paul E. McKenney
2005-03-19 5:03 ` Manfred Spraul
2005-03-19 16:26 ` Ingo Molnar
2005-03-20 6:36 ` Manfred Spraul
2005-03-20 9:25 ` Thomas Gleixner
2005-03-20 16:57 ` Manfred Spraul
2005-03-20 21:38 ` Bill Huey
2005-03-20 21:59 ` Bill Huey
2005-03-18 10:03 ` Ingo Molnar
2005-03-18 11:30 ` Ingo Molnar
2005-03-18 16:48 ` Esben Nielsen
2005-03-18 17:19 ` Ingo Molnar
2005-03-20 13:29 ` Esben Nielsen
2005-03-20 22:38 ` Paul E. McKenney
2005-03-20 23:23 ` Esben Nielsen
2005-03-22 5:53 ` Paul E. McKenney
2005-03-22 8:55 ` Esben Nielsen
2005-03-22 9:20 ` Ingo Molnar
2005-03-22 10:19 ` Esben Nielsen
2005-03-23 5:40 ` Paul E. McKenney
2005-03-23 11:44 ` Esben Nielsen
2005-03-24 7:02 ` Paul E. McKenney
2005-03-22 10:56 ` Ingo Molnar
2005-03-22 11:39 ` Esben Nielsen
2005-03-22 13:10 ` Ingo Molnar
2005-03-22 15:08 ` Esben Nielsen
2005-03-18 15:48 ` Paul E. McKenney
2005-03-18 11:38 ` Ingo Molnar
2005-03-18 12:56 ` Bill Huey
2005-03-18 13:17 ` Bill Huey
2005-03-18 15:57 ` Paul E. McKenney
2005-03-18 16:02 ` Ingo Molnar
2005-03-18 16:55 ` Esben Nielsen
2005-03-22 10:04 ` Bill Huey
2005-03-22 10:17 ` Bill Huey
2005-03-22 10:34 ` Bill Huey
2005-03-22 10:38 ` Esben Nielsen
2005-03-18 22:26 ` Herbert Xu
2005-03-19 16:31 ` Ingo Molnar
2005-03-20 8:01 ` Kyle Moffett
2005-03-22 8:08 ` Ingo Molnar
2005-03-18 15:54 ` Paul E. McKenney
2005-03-18 15:58 ` Ingo Molnar
2009-06-11 22:57 real-time preemption " James Huang
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