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cpu/hotplug: Add new {add,remove}_cpu() functions 

The new functions use device_{online,offline}() which are userspace safe.

This is in preparation to move cpu_{up, down} kernel users to use a safer
interface that is not racy with userspace.

Suggested-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lkml.kernel.org/r/20200323135110.30522-2-qais.yousef@arm.com
This commit is contained in:
Qais Yousef 2020-03-23 13:50:54 +00:00 committed by Thomas Gleixner
parent fd3eafda8f
commit 93ef1429e5
2 changed files with 26 additions and 0 deletions
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2
include/linux/cpu.h
View File

@ -89,6 +89,7 @@ extern ssize_t arch_cpu_release(const char *, size_t);
#ifdef CONFIG_SMP
extern bool cpuhp_tasks_frozen;
int cpu_up(unsigned int cpu);
int add_cpu(unsigned int cpu);
void notify_cpu_starting(unsigned int cpu);
extern void cpu_maps_update_begin(void);
extern void cpu_maps_update_done(void);
@ -118,6 +119,7 @@ extern void cpu_hotplug_disable(void);
extern void cpu_hotplug_enable(void);
void clear_tasks_mm_cpumask(int cpu);
int cpu_down(unsigned int cpu);
int remove_cpu(unsigned int cpu);
#else /* CONFIG_HOTPLUG_CPU */

24
kernel/cpu.c
View File

@ -1057,6 +1057,18 @@ int cpu_down(unsigned int cpu)
}
EXPORT_SYMBOL(cpu_down);
int remove_cpu(unsigned int cpu)
{
int ret;
lock_device_hotplug();
ret = device_offline(get_cpu_device(cpu));
unlock_device_hotplug();
return ret;
}
EXPORT_SYMBOL_GPL(remove_cpu);
#else
#define takedown_cpu NULL
#endif /*CONFIG_HOTPLUG_CPU*/
@ -1209,6 +1221,18 @@ int cpu_up(unsigned int cpu)
}
EXPORT_SYMBOL_GPL(cpu_up);
int add_cpu(unsigned int cpu)
{
int ret;
lock_device_hotplug();
ret = device_online(get_cpu_device(cpu));
unlock_device_hotplug();
return ret;
}
EXPORT_SYMBOL_GPL(add_cpu);
#ifdef CONFIG_PM_SLEEP_SMP
static cpumask_var_t frozen_cpus;