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Date: Fri, 8 Feb 2013 16:52:21 -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 04/40] cpu: Restructure FROZEN state handling
On Thu, Jan 31, 2013 at 12:11:15PM -0000, Thomas Gleixner wrote:
> There are only a few callbacks which really care about FROZEN
> vs. !FROZEN. No need to have extra states for this.
>
> Publish the frozen state in an extra variable which is updated under
> the hotplug lock and let the users interested deal with it w/o
> imposing that extra state checks on everyone.
>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Getting rid of all the _FROZEN variants of the notifier actions would
be good!
Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> ---
> kernel/cpu.c | 66 ++++++++++++++++++++++++-----------------------------------
> 1 file changed, 27 insertions(+), 39 deletions(-)
>
> Index: linux-2.6/kernel/cpu.c
> ===================================================================
> --- linux-2.6.orig/kernel/cpu.c
> +++ linux-2.6/kernel/cpu.c
> @@ -25,6 +25,7 @@
> #ifdef CONFIG_SMP
> /* Serializes the updates to cpu_online_mask, cpu_present_mask */
> static DEFINE_MUTEX(cpu_add_remove_lock);
> +static bool cpuhp_tasks_frozen;
>
> /*
> * The following two API's must be used when attempting
> @@ -148,27 +149,30 @@ int __ref register_cpu_notifier(struct n
> return ret;
> }
>
> -static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
> +static int __cpu_notify(unsigned long val, unsigned int cpu, int nr_to_call,
> int *nr_calls)
> {
> + unsigned long mod = cpuhp_tasks_frozen ? CPU_TASKS_FROZEN : 0;
> + void *hcpu = (void *)(long)cpu;
> +
> int ret;
>
> - ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
> + ret = __raw_notifier_call_chain(&cpu_chain, val | mod, hcpu, nr_to_call,
> nr_calls);
>
> return notifier_to_errno(ret);
> }
>
> -static int cpu_notify(unsigned long val, void *v)
> +static int cpu_notify(unsigned long val, unsigned int cpu)
> {
> - return __cpu_notify(val, v, -1, NULL);
> + return __cpu_notify(val, cpu, -1, NULL);
> }
>
> #ifdef CONFIG_HOTPLUG_CPU
>
> -static void cpu_notify_nofail(unsigned long val, void *v)
> +static void cpu_notify_nofail(unsigned long val, unsigned int cpu)
> {
> - BUG_ON(cpu_notify(val, v));
> + BUG_ON(cpu_notify(val, cpu));
> }
> EXPORT_SYMBOL(register_cpu_notifier);
>
> @@ -237,23 +241,17 @@ static inline void check_for_tasks(int c
> write_unlock_irq(&tasklist_lock);
> }
>
> -struct take_cpu_down_param {
> - unsigned long mod;
> - void *hcpu;
> -};
> -
> /* Take this CPU down. */
> static int __ref take_cpu_down(void *_param)
> {
> - struct take_cpu_down_param *param = _param;
> - int err;
> + int 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 | param->mod, param->hcpu);
> + cpu_notify(CPU_DYING, cpu);
> /* Park the stopper thread */
> kthread_park(current);
> return 0;
> @@ -263,12 +261,6 @@ static int __ref take_cpu_down(void *_pa
> static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
> {
> int err, nr_calls = 0;
> - void *hcpu = (void *)(long)cpu;
> - unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
> - struct take_cpu_down_param tcd_param = {
> - .mod = mod,
> - .hcpu = hcpu,
> - };
>
> if (num_online_cpus() == 1)
> return -EBUSY;
> @@ -278,21 +270,23 @@ static int __ref _cpu_down(unsigned int
>
> cpu_hotplug_begin();
>
> - err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
> + cpuhp_tasks_frozen = tasks_frozen;
> +
> + err = __cpu_notify(CPU_DOWN_PREPARE, cpu, -1, &nr_calls);
> if (err) {
> nr_calls--;
> - __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
> + __cpu_notify(CPU_DOWN_FAILED, cpu, nr_calls, NULL);
> printk("%s: attempt to take down CPU %u failed\n",
> __func__, cpu);
> goto out_release;
> }
> smpboot_park_threads(cpu);
>
> - err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
> + err = __stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
> if (err) {
> /* CPU didn't die: tell everyone. Can't complain. */
> smpboot_unpark_threads(cpu);
> - cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
> + cpu_notify_nofail(CPU_DOWN_FAILED, cpu);
> goto out_release;
> }
> BUG_ON(cpu_online(cpu));
> @@ -311,14 +305,14 @@ static int __ref _cpu_down(unsigned int
> __cpu_die(cpu);
>
> /* CPU is completely dead: tell everyone. Too late to complain. */
> - cpu_notify_nofail(CPU_DEAD | mod, hcpu);
> + cpu_notify_nofail(CPU_DEAD, cpu);
>
> check_for_tasks(cpu);
>
> out_release:
> cpu_hotplug_done();
> if (!err)
> - cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);
> + cpu_notify_nofail(CPU_POST_DEAD, cpu);
> return err;
> }
>
> @@ -345,10 +339,8 @@ EXPORT_SYMBOL(cpu_down);
> /* Requires cpu_add_remove_lock to be held */
> static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
> {
> - int ret, nr_calls = 0;
> - void *hcpu = (void *)(long)cpu;
> - unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
> struct task_struct *idle;
> + int ret, nr_calls = 0;
>
> cpu_hotplug_begin();
>
> @@ -367,7 +359,9 @@ static int __cpuinit _cpu_up(unsigned in
> if (ret)
> goto out;
>
> - ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
> + cpuhp_tasks_frozen = tasks_frozen;
> +
> + ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls);
> if (ret) {
> nr_calls--;
> printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
> @@ -385,11 +379,11 @@ static int __cpuinit _cpu_up(unsigned in
> smpboot_unpark_threads(cpu);
>
> /* Now call notifier in preparation. */
> - cpu_notify(CPU_ONLINE | mod, hcpu);
> + cpu_notify(CPU_ONLINE, cpu);
>
> out_notify:
> if (ret != 0)
> - __cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
> + __cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL);
> out:
> cpu_hotplug_done();
>
> @@ -627,13 +621,7 @@ core_initcall(cpu_hotplug_pm_sync_init);
> */
> void __cpuinit notify_cpu_starting(unsigned int cpu)
> {
> - unsigned long val = CPU_STARTING;
> -
> -#ifdef CONFIG_PM_SLEEP_SMP
> - if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
> - val = CPU_STARTING_FROZEN;
> -#endif /* CONFIG_PM_SLEEP_SMP */
> - cpu_notify(val, (void *)(long)cpu);
> + cpu_notify(CPU_STARTING, cpu);
> }
>
> #endif /* CONFIG_SMP */
>
>
--
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