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From: Thomas Gleixner <tglx@linutronix.de>
To: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	linux-arch@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
	Rusty Russell <rusty@rustcorp.com.au>,
	"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: Fri, 20 Apr 2012 16:18:04 +0200 (CEST)	[thread overview]
Message-ID: <alpine.LFD.2.02.1204201602330.2542@ionos> (raw)
In-Reply-To: <4F916AF3.7020301@linux.vnet.ibm.com>

On Fri, 20 Apr 2012, Srivatsa S. Bhat wrote:
> > This first part moves the idle thread management for non-boot cpus
> > into the core. fork_idle() is called in a workqueue as it is
> > implemented in a few architectures already. This is necessary when not
> > all cpus are brought up by the early boot code as otherwise we would
> > take a ref on the user task VM of the thread which brings the cpu up
> > via the sysfs interface.
> > 
> 
> 
> Do you have a git tree where you have made these patches available?
> That would be pretty useful, so that we can build on whatever you have

Not yet, but I'll stick that into a tip/ branch.

> already done.. Myself and Nikunj had some initial design/ideas on reducing
> the duplication in architecture code, related to managing the setting
> of the cpu in the online mask, sending out CPU_STARTING notifiers etc
> from generic code..

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.

Flat notifiers are not working for this as they do not allow a tree
structure and prevent us to do things in parallel.

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.

I've already done a prototype for kthread park/unpark and converted
softirq over to use it. That makes the complete softirq notifier go
away and let the core code handle the thread creation / start / park /
unpark. It's pretty hacky right now, but I'm going to push on this
next, once I have a better idea how to express the dependency tree.

Thanks,

	tglx

  reply	other threads:[~2012-04-20 14:18 UTC|newest]

Thread overview: 87+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-20 13:05 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
2012-04-20 13:05   ` Thomas Gleixner
2012-04-23  7:58   ` Jesper Nilsson
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 13:05   ` Thomas Gleixner
2012-04-20 20:07   ` Yinghai Lu
2012-04-20 20:07     ` Yinghai Lu
2012-04-21  2:07   ` Stephen Rothwell
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 13:05   ` Thomas Gleixner
2012-04-20 16:21   ` Sam Ravnborg
2012-04-20 16:21     ` Sam Ravnborg
2012-04-20 18:55     ` Thomas Gleixner
2012-04-20 18:55       ` Thomas Gleixner
2012-04-21  2:20   ` Stephen Rothwell
2012-04-21  2:20     ` Stephen Rothwell
2012-04-21  2:25   ` Frank Rowand
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 [this message]
2012-04-24 18:44     ` Konrad Rzeszutek Wilk
2012-05-21  1:42     ` Rusty Russell
2012-05-21  8:25       ` Thomas Gleixner
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
2012-04-22 21:01   ` Chris Metcalf
2012-04-22 21:01   ` Chris Metcalf
2012-04-30  8:05 ` Santosh Shilimkar

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