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Date: Thu, 31 Jan 2013 12:23:42 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Thomas Gleixner <tglx@linutronix.de>
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
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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?

Methinks Tejun needed a cc on this lot ;)