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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	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>
Subject: Re: [patch 00/40] CPU hotplug rework - episode I
Date: Fri, 1 Feb 2013 08:59:49 +1100	[thread overview]
Message-ID: <CA+55aFx=cv+HxKGx+oQk4iLnnTGO7P0u3+DnvuOWbYzM-wvEeQ@mail.gmail.com> (raw)
In-Reply-To: <alpine.LFD.2.02.1301312233480.11905@ionos>

On Fri, Feb 1, 2013 at 8:48 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
>> Methinks Tejun needed a cc on this lot ;)
>
> Not really.

I think we want as many people as possible cc'd on this. You may think
it's an obvious improvement, but maybe it's just because you now
understand the code because you wrote it yourself, not because it's
*actually* better.

Having some explicitly documented states may be nice, but do we need
eleven of them? And do we want to expose them? At least not for the
f*cking notifiers, I hope. Notifiers are a disgrace, and almost all of
them are a major design mistake. They all have locking problems, the
introduce internal arbitrary API's that are hard to fix later (because
you have random people who decided to hook into them, which is the
whole *point* of those notifier chains).

Since the patches themselves weren't cc'd, I don't know if you
actually made each state transition do those insane notifiers or not,
but I seriously hope you didn't. With that many states, hopefully the
idea is that you don't have any notifiers at all, and you just then
call the people associated with a particular state directly. Yes? No?

Because if this adds tons of new notifiers, I'm going to say that we
need about a hundred people signing off on the patches.  Part of your
explanation made me think you got rid of the notifiers, but then it
became clear that you just renamed them as "state callbacks". If
that's some generic exposed interface, I'll NAK it. No way in hell do
we want to expose eleven states with some random generic "SMP state
callback interface". F*ck no.

                Linus

  reply	other threads:[~2013-01-31 22:00 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
2013-01-31 21:59     ` Linus Torvalds [this message]
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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