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Date: Mon, 11 Feb 2013 12:17:14 -0800
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Rusty Russell <rusty@...tcorp.com.au>,
"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
Arjan van de Veen <arjan@...radead.org>,
Paul Turner <pjt@...gle.com>,
Richard Weinberger <rw@...utronix.de>,
Magnus Damm <magnus.damm@...il.com>
Subject: Re: [patch 08/40] cpu: hotplug: Convert the hotplugged processor
work to a state machine
On Thu, Jan 31, 2013 at 12:11:18PM -0000, Thomas Gleixner wrote:
> Move the functions which need to run on the hotplugged processor into
> a state machine array and let the code iterate through these functions.
>
> In a later state, this will grow synchronization points between the
> control processor and the hotplugged processor, so we can move the
> various architecture implementations of the synchronizations to the
> core.
>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> ---
> include/linux/cpuhotplug.h | 4 ++
> kernel/cpu.c | 70 +++++++++++++++++++++++++++++++++++----------
> 2 files changed, 59 insertions(+), 15 deletions(-)
>
> Index: linux-2.6/include/linux/cpuhotplug.h
> ===================================================================
> --- linux-2.6.orig/include/linux/cpuhotplug.h
> +++ linux-2.6/include/linux/cpuhotplug.h
> @@ -7,6 +7,10 @@ enum cpuhp_states {
> CPUHP_NOTIFY_PREPARE,
> CPUHP_NOTIFY_DEAD,
> CPUHP_BRINGUP_CPU,
> + CPUHP_AP_OFFLINE,
> + CPUHP_AP_NOTIFY_STARTING,
> + CPUHP_AP_NOTIFY_DYING,
> + CPUHP_AP_MAX,
> CPUHP_TEARDOWN_CPU,
> CPUHP_PERCPU_THREADS,
> CPUHP_NOTIFY_ONLINE,
> Index: linux-2.6/kernel/cpu.c
> ===================================================================
> --- linux-2.6.orig/kernel/cpu.c
> +++ linux-2.6/kernel/cpu.c
> @@ -32,6 +32,7 @@ struct cpuhp_step {
> };
>
> static struct cpuhp_step cpuhp_bp_states[];
> +static struct cpuhp_step cpuhp_ap_states[];
>
> #ifdef CONFIG_SMP
> /* Serializes the updates to cpu_online_mask, cpu_present_mask */
> @@ -216,6 +217,12 @@ static int bringup_cpu(unsigned int cpu)
> return 0;
> }
>
> +static int notify_starting(unsigned int cpu)
> +{
> + cpu_notify(CPU_STARTING, cpu);
> + return 0;
> +}
> +
> #ifdef CONFIG_HOTPLUG_CPU
> EXPORT_SYMBOL(register_cpu_notifier);
>
> @@ -303,17 +310,26 @@ static int notify_down_prepare(unsigned
> return err;
> }
>
> +static int notify_dying(unsigned int cpu)
> +{
> + cpu_notify(CPU_DYING, cpu);
> + return 0;
> +}
> +
> /* Take this CPU down. */
> static int __ref take_cpu_down(void *_param)
> {
> - int err, cpu = smp_processor_id();
> + int step, err, cpu = smp_processor_id();
>
> /* Ensure this CPU doesn't handle any more interrupts. */
> err = __cpu_disable();
> if (err < 0)
> return err;
>
> - cpu_notify(CPU_DYING, cpu);
> + for (step = CPUHP_AP_MAX; step >= CPUHP_AP_OFFLINE; step--) {
> + if (cpuhp_ap_states[step].teardown)
> + cpuhp_ap_states[step].teardown(cpu);
> + }
> /* Park the stopper thread */
> kthread_park(current);
> return 0;
> @@ -357,6 +373,7 @@ static int notify_dead(unsigned int cpu)
> #define notify_down_prepare NULL
> #define takedown_cpu NULL
> #define notify_dead NULL
> +#define notify_dying NULL
> #endif
>
> #ifdef CONFIG_HOTPLUG_CPU
> @@ -429,6 +446,24 @@ out:
> EXPORT_SYMBOL(cpu_down);
> #endif /*CONFIG_HOTPLUG_CPU*/
>
> +/**
> + * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
> + * @cpu: cpu that just started
> + *
> + * This function calls the cpu_chain notifiers with CPU_STARTING.
> + * It must be called by the arch code on the new cpu, before the new cpu
> + * enables interrupts and before the "boot" cpu returns from __cpu_up().
> + */
> +void notify_cpu_starting(unsigned int cpu)
> +{
> + int step;
> +
> + for (step = CPUHP_AP_OFFLINE; step < CPUHP_AP_MAX; step++) {
> + if (cpuhp_ap_states[step].startup)
> + cpuhp_ap_states[step].startup(cpu);
> + }
> +}
> +
> static void undo_cpu_up(unsigned int cpu, int step)
> {
> while (step--) {
> @@ -703,19 +738,6 @@ core_initcall(cpu_hotplug_pm_sync_init);
>
> #endif /* CONFIG_PM_SLEEP_SMP */
>
> -/**
> - * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
> - * @cpu: cpu that just started
> - *
> - * This function calls the cpu_chain notifiers with CPU_STARTING.
> - * It must be called by the arch code on the new cpu, before the new cpu
> - * enables interrupts and before the "boot" cpu returns from __cpu_up().
> - */
> -void __cpuinit notify_cpu_starting(unsigned int cpu)
> -{
> - cpu_notify(CPU_STARTING, cpu);
> -}
> -
> #endif /* CONFIG_SMP */
>
> /* Boot processor state steps */
> @@ -764,6 +786,24 @@ static struct cpuhp_step cpuhp_bp_states
> },
> };
>
> +/* Application processor state steps */
> +static struct cpuhp_step cpuhp_ap_states[] = {
> +#ifdef CONFIG_SMP
> + [CPUHP_AP_NOTIFY_STARTING] = {
> + .startup = notify_starting,
> + .teardown = NULL,
> + },
> + [CPUHP_AP_NOTIFY_DYING] = {
> + .startup = NULL,
> + .teardown = notify_dying,
> + },
> +#endif
> + [CPUHP_MAX] = {
> + .startup = NULL,
> + .teardown = NULL,
> + },
> +};
> +
> /*
> * cpu_bit_bitmap[] is a special, "compressed" data structure that
> * represents all NR_CPUS bits binary values of 1<<nr.
>
>
--
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