From: Thomas Gleixner <tglx@linutronix.de>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-arch@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Ingo Molnar <mingo@kernel.org>,
Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [patch 00/18] SMP: Boot and CPU hotplug refactoring - Part 1
Date: Mon, 21 May 2012 10:25:21 +0200 (CEST) [thread overview]
Message-ID: <alpine.LFD.2.02.1205211013440.3231@ionos> (raw)
In-Reply-To: <871ume48ds.fsf@rustcorp.com.au>
On Mon, 21 May 2012, Rusty Russell wrote:
> On Fri, 20 Apr 2012 16:18:04 +0200 (CEST), Thomas Gleixner <tglx@linutronix.de> wrote:
> > On Fri, 20 Apr 2012, Srivatsa S. Bhat wrote:
> > The whole notifier business needs a redesign as well, because we don't
> > have a way to express proper dependencies, we add random notifier
> > points and the teardown path is ass backwards. The whole thing wants
> > to be a tree which can be walked in either direction and from any
> > point. Right now we cut the trunk first and keep the single limb up
> > with a helicopter and start dismantling it.
>
> But there are two ways to do it. One is to eliminate the need for
> callbacks. The other is to make a full dependency-based callback
What do you mean with fully eliminating the need for callbacks. Do you
want to put the necessary bringup/shutdown function calls just in the
core code so we get rid of the notifiers or do you have something
different in mind ?
> system.
>
> Let's try the first before the second. I implemented a full dep-based
> system for initcalls once, and it was not as nice as I'd hoped.
Yeah, a full dependency thing might be overkill.
> > Flat notifiers are not working for this as they do not allow a tree
> > structure and prevent us to do things in parallel.
>
> Not sure whether calling notifiers in parallel is going to be a big win:
> they'll end up fighting over the cpu we're taking down. But I could be
> wrong.
I'm not going to aim for parallel in the first place. That was just an
idea and if we chose the right implementation then parallelism can be
added later.
> > That really needs to be completely reworked. There is also a lot of
> > stuff which wants to be moved into the starting/dying CPU
> > context. Right now we kinda do that by trampling on the CPU with a
> > high prio stomper thread, but that's really just a bandaid and steady
> > cause of trouble.
> >
> > If you look at facilities which use kthreads, then there is lots other
> > setup which does not need a notifier at all, as it can be done in the
> > context of the thread when we have a way to start/park those threads
> > at the right time in the up/down process.
>
> That's a very nice idea. Should be simpler for kthreads park/unpark
> themselves, rather than having some notifier to kill them.
Well, something needs to tell them to park/unpark, but what should
move into the thread is the setup/teardown of context.
> The original concept of stopping the machine for cpu hotplug and trying
> not to effect any other kernel code has jumped the shark: I think we
> need to look seriously at a complete rewrite where we don't use
> stop_machine.
Yep. Working on it. :)
Thanks,
tglx
next prev parent reply other threads:[~2012-05-21 8:25 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-20 13:05 [patch 00/18] SMP: Boot and CPU hotplug refactoring - Part 1 Thomas Gleixner
2012-04-20 13:05 ` [patch 01/18] m32r: Remove pointless function prototypes Thomas Gleixner
2012-04-28 9:01 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:05 ` [patch 02/18] smp: Add task_struct argument to __cpu_up() Thomas Gleixner
2012-04-23 7:58 ` Jesper Nilsson
2012-04-28 9:02 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:05 ` [patch 03/18] smp: Add generic smpboot facility Thomas Gleixner
2012-04-20 20:07 ` Yinghai Lu
2012-04-21 2:07 ` Stephen Rothwell
2012-04-28 9:04 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:05 ` [patch 04/18] smp: Provide generic idle thread allocation Thomas Gleixner
2012-04-20 16:21 ` Sam Ravnborg
2012-04-20 18:55 ` Thomas Gleixner
2012-04-21 2:20 ` Stephen Rothwell
2012-04-21 2:25 ` Frank Rowand
2012-04-28 9:05 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:05 ` [patch 05/18] x86: Add task_struct argument to smp_ops.cpu_up Thomas Gleixner
2012-04-28 9:05 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:05 ` [patch 06/18] x86: Use generic idle thread allocation Thomas Gleixner
2012-04-28 9:06 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:05 ` [patch 07/18] powerpc: " Thomas Gleixner
2012-04-28 9:07 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-28 22:51 ` Benjamin Herrenschmidt
2012-04-20 13:05 ` [patch 08/18] ia64: " Thomas Gleixner
2012-04-28 9:08 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:05 ` [patch 09/18] arm: " Thomas Gleixner
2012-04-28 9:09 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:05 ` [patch 11/18] hexagon: " Thomas Gleixner
2012-04-24 16:47 ` Richard Kuo
2012-04-28 9:10 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:05 ` [patch 10/18] mips: " Thomas Gleixner
2012-04-28 9:10 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:05 ` [patch 12/18] s390: " Thomas Gleixner
2012-04-23 7:09 ` Martin Schwidefsky
2012-04-28 9:11 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:05 ` [patch 13/18] blackfin: " Thomas Gleixner
2012-04-28 9:13 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:05 ` [patch 14/18] cris: " Thomas Gleixner
2012-04-23 7:57 ` Jesper Nilsson
2012-04-28 9:12 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:05 ` [patch 15/18] sh: " Thomas Gleixner
2012-04-21 3:18 ` Paul Mundt
2012-04-28 9:14 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:05 ` [patch 16/18] alpha: " Thomas Gleixner
2012-04-28 9:15 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:05 ` [patch 17/18] parisc: " Thomas Gleixner
2012-04-28 9:16 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:05 ` [patch 18/18] sparc: " Thomas Gleixner
2012-04-22 19:52 ` David Miller
2012-04-28 9:15 ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2012-04-20 13:16 ` [patch 00/18] SMP: Boot and CPU hotplug refactoring - Part 1 Thomas Gleixner
2012-04-20 13:21 ` Peter Zijlstra
2012-04-20 13:47 ` Thomas Gleixner
2012-04-21 0:08 ` Suresh Siddha
2012-05-03 9:41 ` Thomas Gleixner
2012-05-03 23:42 ` Suresh Siddha
2012-05-03 17:43 ` [tip:smp/hotplug] smp, idle: Allocate idle thread for each possible cpu during boot tip-bot for Suresh Siddha
2012-04-20 15:42 ` [patch 00/18] SMP: Boot and CPU hotplug refactoring - Part 1 Tejun Heo
2012-04-20 15:49 ` Peter Zijlstra
2012-04-20 15:56 ` Thomas Gleixner
2012-04-20 13:56 ` Srivatsa S. Bhat
2012-04-20 14:18 ` Thomas Gleixner
2012-04-24 18:44 ` Konrad Rzeszutek Wilk
2012-05-21 1:42 ` Rusty Russell
2012-05-21 8:25 ` Thomas Gleixner [this message]
2012-05-22 0:53 ` Rusty Russell
2012-04-20 14:06 ` richard -rw- weinberger
2012-04-20 14:19 ` Thomas Gleixner
2012-04-20 14:27 ` James Bottomley
2012-04-20 17:55 ` Paul E. McKenney
2012-04-20 23:11 ` Venki Pallipadi
2012-04-21 1:04 ` Frank Rowand
2012-04-21 1:55 ` Frank Rowand
2012-04-22 21:01 ` Chris Metcalf
2012-04-30 8:05 ` Santosh Shilimkar
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