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From: Thomas Gleixner <tglx@linutronix.de>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
	Peter Zijlstra <peterz@infradead.org>,
	Rusty Russell <rusty@rustcorp.com.au>,
	Paul McKenney <paulmck@linux.vnet.ibm.com>,
	"Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
	Arjan van de Veen <arjan@infradead.org>,
	Paul Turner <pjt@google.com>,
	Richard Weinberger <rw@linutronix.de>,
	Magnus Damm <magnus.damm@gmail.com>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [patch 00/40] CPU hotplug rework - episode I
Date: Thu, 31 Jan 2013 22:48:41 +0100 (CET)	[thread overview]
Message-ID: <alpine.LFD.2.02.1301312233480.11905@ionos> (raw)
In-Reply-To: <20130131122342.31b28664.akpm@linux-foundation.org>

On Thu, 31 Jan 2013, Andrew Morton wrote:

> On Thu, 31 Jan 2013 15:44:10 -0000
> Thomas Gleixner <tglx@linutronix.de> wrote:
> 
> > At the end hotplug should run through an array of callbacks on both
> > sides with explicit core synchronization points. The ordering should
> > look like this:
> > 
> > CPUHP_OFFLINE                   // Start state.
> > CPUHP_PREP_<hardware>           // Kick CPU into life / let it die
> > CPUHP_PREP_<datastructures>     // Get datastructures set up / freed.
> > CPUHP_PREP_<threads>            // Create threads for cpu
> > CPUHP_SYNC			// Synchronization point
> > CPUHP_INIT_<hardware>		// Startup/teardown on the CPU (interrupts, timers ...)
> > CPUHP_SCHED_<stuff on CPU>      // Unpark/park per cpu local threads on the CPU.
> > CPUHP_ENABLE_<stuff_on_CPU>	// Enable/disable facilities 
> > CPUHP_SYNC			// Synchronization point
> > CPUHP_SCHED                     // Expose/remove CPU from general scheduler.
> > CPUHP_ONLINE                    // Final state
> 
> What does CPUHP_SYNC do?

This is a future step which makes sure that the cpu which controls the
bringup and the teardown of the hotplugged cpu are synchronizing at
some point. Right now, we have this synchronization burried somewhere
in the architecture code and of course every arch does it different
versus the generic bringup/teardown mechanisms.
 
> Methinks Tejun needed a cc on this lot ;)

Not really. The workqueue hotplug scheme is today one of the sanest in
that area. Earlier versions have been a prime example of hotplug hell!

TJ has converted it via the notifier priorities to a symetric
startup/teardown scheme already. So the conversion is a no brainer and
no real change.

Sure, I should have spent the cycles to add every file owner to the cc
list, but due to brain damage caused by decoding the current hotplug
maze I skipped that painful exercise relying on you to fix it up for
me :)

Thanks,

	tglx




  reply	other threads:[~2013-01-31 21:48 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-01-31 15:44 [patch 00/40] CPU hotplug rework - episode I Thomas Gleixner
2013-01-31 12:11 ` [patch 01/40] smpboot: Allow selfparking per cpu threads Thomas Gleixner
2013-02-09  0:29   ` Paul E. McKenney
2013-02-14 17:46   ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2013-01-31 12:11 ` [patch 02/40] stop_machine: Store task reference in a separate per cpu variable Thomas Gleixner
2013-02-09  0:33   ` Paul E. McKenney
2013-02-14 17:47   ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2013-01-31 12:11 ` [patch 03/40] stop_machine: Use smpboot threads Thomas Gleixner
2013-02-09  0:39   ` Paul E. McKenney
2013-02-14 17:49   ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2013-01-31 12:11 ` [patch 04/40] cpu: Restructure FROZEN state handling Thomas Gleixner
2013-02-09  0:52   ` Paul E. McKenney
2014-10-09 16:53   ` Borislav Petkov
2013-01-31 12:11 ` [patch 05/40] cpu: Restructure cpu_down code Thomas Gleixner
2013-02-09  0:49   ` Paul E. McKenney
2014-10-09 17:05   ` Borislav Petkov
2013-01-31 12:11 ` [patch 06/40] cpu: hotplug: Split out cpu down functions Thomas Gleixner
2013-02-09  0:54   ` Paul E. McKenney
2013-01-31 12:11 ` [patch 07/40] cpu: hotplug: Convert to a state machine for the control processor Thomas Gleixner
2013-02-11 20:09   ` Paul E. McKenney
2013-01-31 12:11 ` [patch 08/40] cpu: hotplug: Convert the hotplugged processor work to a state machine Thomas Gleixner
2013-02-11 20:17   ` Paul E. McKenney
2013-01-31 12:11 ` [patch 10/40] sched: Convert to state machine callbacks Thomas Gleixner
2013-02-11 23:46   ` Paul E. McKenney
2013-01-31 12:11 ` [patch 09/40] cpu: hotplug: Implement setup/removal interface Thomas Gleixner
2013-02-01 13:44   ` Hillf Danton
2013-02-01 13:52     ` Thomas Gleixner
2013-01-31 12:11 ` [patch 11/40] x86: uncore: Move teardown callback to CPU_DEAD Thomas Gleixner
2013-01-31 12:11 ` [patch 12/40] x86: uncore: Convert to hotplug state machine Thomas Gleixner
2013-01-31 12:11 ` [patch 13/40] perf: " Thomas Gleixner
2013-01-31 12:11 ` [patch 14/40] x86: perf: Convert the core to the " Thomas Gleixner
2013-01-31 12:11 ` [patch 16/40] blackfin: perf: Convert hotplug notifier to " Thomas Gleixner
2013-01-31 12:11 ` [patch 15/40] x86: perf: Convert AMD IBS to hotplug " Thomas Gleixner
2013-01-31 12:11 ` [patch 17/40] powerpc: perf: Convert book3s notifier to state machine callbacks Thomas Gleixner
2013-01-31 12:11 ` [patch 18/40] s390: perf: Convert the hotplug " Thomas Gleixner
2013-01-31 12:11 ` [patch 19/40] sh: perf: Convert the hotplug notifiers " Thomas Gleixner
2013-01-31 12:11 ` [patch 21/40] sched: Convert the migration callback to hotplug states Thomas Gleixner
2013-01-31 12:11 ` [patch 20/40] perf: Remove perf cpu notifier code Thomas Gleixner
2013-01-31 12:11 ` [patch 22/40] workqueue: Convert to state machine callbacks Thomas Gleixner
2013-01-31 12:11 ` [patch 23/40] cpufreq: Convert to hotplug state machine Thomas Gleixner
2013-01-31 12:11 ` [patch 24/40] arm64: Convert generic timers " Thomas Gleixner
2013-01-31 12:11 ` [patch 25/40] arm: Convert VFP hotplug notifiers to " Thomas Gleixner
2013-01-31 12:11 ` [patch 26/40] arm: perf: Convert to hotplug " Thomas Gleixner
2013-01-31 12:11 ` [patch 27/40] virt: Convert kvm hotplug to " Thomas Gleixner
2013-01-31 12:11 ` [patch 28/40] cpuhotplug: Remove CPU_STARTING notifier Thomas Gleixner
2013-01-31 12:11 ` [patch 29/40] s390: Convert vtime to hotplug state machine Thomas Gleixner
2013-01-31 12:11 ` [patch 30/40] x86: tboot: Convert " Thomas Gleixner
2013-01-31 12:11 ` [patch 31/40] sched: Convert fair nohz balancer " Thomas Gleixner
2013-01-31 12:11 ` [patch 33/40] hrtimer: Convert " Thomas Gleixner
2013-01-31 12:11 ` [patch 32/40] rcu: Convert rcutree " Thomas Gleixner
2013-02-12  0:01   ` Paul E. McKenney
2013-02-12 15:50     ` Paul E. McKenney
2013-01-31 12:11 ` [patch 34/40] cpuhotplug: Remove CPU_DYING notifier Thomas Gleixner
2013-01-31 12:11 ` [patch 35/40] timers: Convert to hotplug state machine Thomas Gleixner
2013-01-31 12:11 ` [patch 36/40] profile: Convert ot " Thomas Gleixner
2013-01-31 12:11 ` [patch 37/40] x86: x2apic: Convert to cpu " Thomas Gleixner
2013-01-31 12:11 ` [patch 38/40] smp: Convert core to " Thomas Gleixner
2013-01-31 12:11 ` [patch 39/40] relayfs: Convert " Thomas Gleixner
2013-01-31 12:11 ` [patch 40/40] slab: " Thomas Gleixner
2013-01-31 20:23 ` [patch 00/40] CPU hotplug rework - episode I Andrew Morton
2013-01-31 21:48   ` Thomas Gleixner [this message]
2013-01-31 21:59     ` Linus Torvalds
2013-01-31 22:44       ` Thomas Gleixner
2013-01-31 22:55         ` Linus Torvalds
2013-02-01 10:51           ` Thomas Gleixner
2013-02-07  4:01             ` Rusty Russell
2013-02-09  0:28 ` Paul E. McKenney

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