linux-kernel - Re: [Patch 3/7] smpboot: Provide infrastructure for percpu hotplug threads

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Date:	Sat, 21 Jul 2012 14:56:47 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Namhyung Kim <namhyung@...nel.org>
Subject: Re: [Patch 3/7] smpboot: Provide infrastructure for percpu hotplug
 threads

On 07/16/2012 04:12 PM, Thomas Gleixner wrote:
> Provide a generic interface for setting up and tearing down percpu
> threads.
> 
> On registration the threads for already online cpus are created and
> started. On deregistration (modules) the threads are stoppped.
> 
> During hotplug operations the threads are created, started, parked and
> unparked. The datastructure for registration provides a pointer to
> percpu storage space and optional setup, cleanup, park, unpark
> functions. These functions are called when the thread state changes.
> 
> Each implementation has to provide a function which is queried and
> returns whether the thread should run and the thread function itself.
> 
> The core code handles all state transitions and avoids duplicated code
> in the call sites.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

Elegant design and very beautiful code!
It was such a pleasure to read and review it :-)

Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>

[ A minor nit below ]

> ---
>  include/linux/smpboot.h |   43 +++++++++
>  kernel/cpu.c            |   10 +-
>  kernel/smpboot.c        |  229 ++++++++++++++++++++++++++++++++++++++++++++++++
>  kernel/smpboot.h        |    4 
>  4 files changed, 285 insertions(+), 1 deletion(-)
> 
> +
> +/**
> + * smpboot_thread_fn - percpu hotplug thread loop function
> + * @void:	thread data pointer

s/void/data

> + *
> + * Checks for thread stop and park conditions. Calls the necessary
> + * setup, cleanup, park and unpark functions for the registered
> + * thread.
> + *
> + * Returns 1 when the thread should exit, 0 otherwise.
> + */
> +static int smpboot_thread_fn(void *data)
> +{
> +	struct smpboot_thread_data *td = data;
> +	struct smp_hotplug_thread *ht = td->ht;
> +

Regards,
Srivatsa S. Bhat

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