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Commit e0b582ec authored by Rusty Russell's avatar Rusty Russell
Browse files

cpumask: convert kernel/cpu.c 



Impact: Reduce kernel stack and memory usage, use new cpumask API.

Use cpumask_var_t for take_cpu_down() stack var, and frozen_cpus.

Note that notify_cpu_starting() can be called before core_initcall
allocates frozen_cpus, but the NULL check is optimized out by gcc for
the CONFIG_CPUMASK_OFFSTACK=n case.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent c309b917

kernel/cpu.c

+29 −19
Original line number Diff line number Diff line
@@ -194,7 +194,7 @@ static int __ref take_cpu_down(void *_param) 
static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)

{

	int err, nr_calls = 0;

	cpumask_t old_allowed, tmp;

	cpumask_var_t old_allowed;

	void *hcpu = (void *)(long)cpu;

	unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;

	struct take_cpu_down_param tcd_param = {
@@ -208,6 +208,9 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen) 
	if (!cpu_online(cpu))

		return -EINVAL;



	if (!alloc_cpumask_var(&old_allowed, GFP_KERNEL))

		return -ENOMEM;



	cpu_hotplug_begin();

	err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,

					hcpu, -1, &nr_calls);
@@ -222,13 +225,11 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen) 
	}



	/* Ensure that we are not runnable on dying cpu */

	old_allowed = current->cpus_allowed;

	cpus_setall(tmp);

	cpu_clear(cpu, tmp);

	set_cpus_allowed_ptr(current, &tmp);

	tmp = cpumask_of_cpu(cpu);

	cpumask_copy(old_allowed, &current->cpus_allowed);

	set_cpus_allowed_ptr(current,

			     cpumask_of(cpumask_any_but(cpu_online_mask, cpu)));



	err = __stop_machine(take_cpu_down, &tcd_param, &tmp);

	err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));

	if (err) {

		/* CPU didn't die: tell everyone.  Can't complain. */

		if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
@@ -254,7 +255,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen) 
	check_for_tasks(cpu);



out_allowed:

	set_cpus_allowed_ptr(current, &old_allowed);

	set_cpus_allowed_ptr(current, old_allowed);

out_release:

	cpu_hotplug_done();

	if (!err) {
@@ -262,6 +263,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen) 
					    hcpu) == NOTIFY_BAD)

			BUG();

	}

	free_cpumask_var(old_allowed);

	return err;

}
@@ -280,7 +282,7 @@ int __ref cpu_down(unsigned int cpu) 


	/*

	 * Make sure the all cpus did the reschedule and are not

	 * using stale version of the cpu_active_map.

	 * using stale version of the cpu_active_mask.

	 * This is not strictly necessary becuase stop_machine()

	 * that we run down the line already provides the required

	 * synchronization. But it's really a side effect and we do not
@@ -344,7 +346,7 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen) 
int __cpuinit cpu_up(unsigned int cpu)

{

	int err = 0;

	if (!cpu_isset(cpu, cpu_possible_map)) {

	if (!cpu_possible(cpu)) {

		printk(KERN_ERR "can't online cpu %d because it is not "

			"configured as may-hotadd at boot time\n", cpu);

#if defined(CONFIG_IA64) || defined(CONFIG_X86_64)
@@ -369,25 +371,25 @@ int __cpuinit cpu_up(unsigned int cpu) 
}



#ifdef CONFIG_PM_SLEEP_SMP

static cpumask_t frozen_cpus;

static cpumask_var_t frozen_cpus;



int disable_nonboot_cpus(void)

{

	int cpu, first_cpu, error = 0;



	cpu_maps_update_begin();

	first_cpu = first_cpu(cpu_online_map);

	first_cpu = cpumask_first(cpu_online_mask);

	/* We take down all of the non-boot CPUs in one shot to avoid races

	 * with the userspace trying to use the CPU hotplug at the same time

	 */

	cpus_clear(frozen_cpus);

	cpumask_clear(frozen_cpus);

	printk("Disabling non-boot CPUs ...\n");

	for_each_online_cpu(cpu) {

		if (cpu == first_cpu)

			continue;

		error = _cpu_down(cpu, 1);

		if (!error) {

			cpu_set(cpu, frozen_cpus);

			cpumask_set_cpu(cpu, frozen_cpus);

			printk("CPU%d is down\n", cpu);

		} else {

			printk(KERN_ERR "Error taking CPU%d down: %d\n",
@@ -413,11 +415,11 @@ void __ref enable_nonboot_cpus(void) 
	/* Allow everyone to use the CPU hotplug again */

	cpu_maps_update_begin();

	cpu_hotplug_disabled = 0;

	if (cpus_empty(frozen_cpus))

	if (cpumask_empty(frozen_cpus))

		goto out;



	printk("Enabling non-boot CPUs ...\n");

	for_each_cpu_mask_nr(cpu, frozen_cpus) {

	for_each_cpu(cpu, frozen_cpus) {

		error = _cpu_up(cpu, 1);

		if (!error) {

			printk("CPU%d is up\n", cpu);
@@ -425,10 +427,18 @@ void __ref enable_nonboot_cpus(void) 
		}

		printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);

	}

	cpus_clear(frozen_cpus);

	cpumask_clear(frozen_cpus);

out:

	cpu_maps_update_done();

}



static int alloc_frozen_cpus(void)

{

	if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))

		return -ENOMEM;

	return 0;

}

core_initcall(alloc_frozen_cpus);

#endif /* CONFIG_PM_SLEEP_SMP */



/**
@@ -444,7 +454,7 @@ void __cpuinit notify_cpu_starting(unsigned int cpu) 
	unsigned long val = CPU_STARTING;



#ifdef CONFIG_PM_SLEEP_SMP

	if (cpu_isset(cpu, frozen_cpus))

	if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))

		val = CPU_STARTING_FROZEN;

#endif /* CONFIG_PM_SLEEP_SMP */

	raw_notifier_call_chain(&cpu_chain, val, (void *)(long)cpu);
@@ -456,7 +466,7 @@ void __cpuinit notify_cpu_starting(unsigned int cpu) 
 * cpu_bit_bitmap[] is a special, "compressed" data structure that

 * represents all NR_CPUS bits binary values of 1<<nr.

 *

 * It is used by cpumask_of_cpu() to get a constant address to a CPU

 * It is used by cpumask_of() to get a constant address to a CPU

 * mask value that has a single bit set only.

 */