On Mon, Mar 23, 2020 at 01:50:54PM +0000, Qais Yousef wrote:
> 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@xxxxxxxxxx>
> Signed-off-by: Qais Yousef <qais.yousef@xxxxxxx>
> CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> CC: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> CC: Helge Deller <deller@xxxxxx>
> CC: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> CC: "David S. Miller" <davem@xxxxxxxxxxxxx>
> CC: Juergen Gross <jgross@xxxxxxxx>
> CC: Mark Rutland <mark.rutland@xxxxxxx>
> CC: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> CC: xen-devel@xxxxxxxxxxxxxxxxxxxx
> CC: linux-parisc@xxxxxxxxxxxxxxx
> CC: sparclinux@xxxxxxxxxxxxxxx
> CC: linuxppc-dev@xxxxxxxxxxxxxxxx
> CC: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> CC: x86@xxxxxxxxxx
> CC: linux-kernel@xxxxxxxxxxxxxxx
> ---
> include/linux/cpu.h | 2 ++
> kernel/cpu.c | 24 ++++++++++++++++++++++++
> 2 files changed, 26 insertions(+)
>
> diff --git a/include/linux/cpu.h b/include/linux/cpu.h
> index 1ca2baf817ed..cf8cf38dca43 100644
> --- a/include/linux/cpu.h
> +++ b/include/linux/cpu.h
> @@ -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 */
>
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index 9c706af713fb..069802f7010f 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -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;
>
> --
> 2.17.1
>
