Commit dc8d37ed authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Thomas Gleixner
Browse files

cpu/SMT: Fix x86 link error without CONFIG_SYSFS 



When CONFIG_SYSFS is disabled, but CONFIG_HOTPLUG_SMT is enabled,
the kernel fails to link:

arch/x86/power/cpu.o: In function `hibernate_resume_nonboot_cpu_disable':
(.text+0x38d): undefined reference to `cpuhp_smt_enable'
arch/x86/power/hibernate.o: In function `arch_resume_nosmt':
hibernate.c:(.text+0x291): undefined reference to `cpuhp_smt_enable'
hibernate.c:(.text+0x29c): undefined reference to `cpuhp_smt_disable'

Move the exported functions out of the #ifdef section into its
own with the correct conditions.

The patch that caused this is marked for stable backports, so
this one may need to be backported as well.

Fixes: ec527c31 ("x86/power: Fix 'nosmt' vs hibernation triple fault during resume")
Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarJiri Kosina <jkosina@suse.cz>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20191210195614.786555-1-arnd@arndb.de
parent c79f46a2

kernel/cpu.c

+72 −71
Original line number Diff line number Diff line
@@ -1909,6 +1909,78 @@ void __cpuhp_remove_state(enum cpuhp_state state, bool invoke) 
}

EXPORT_SYMBOL(__cpuhp_remove_state);



#ifdef CONFIG_HOTPLUG_SMT

static void cpuhp_offline_cpu_device(unsigned int cpu)

{

	struct device *dev = get_cpu_device(cpu);



	dev->offline = true;

	/* Tell user space about the state change */

	kobject_uevent(&dev->kobj, KOBJ_OFFLINE);

}



static void cpuhp_online_cpu_device(unsigned int cpu)

{

	struct device *dev = get_cpu_device(cpu);



	dev->offline = false;

	/* Tell user space about the state change */

	kobject_uevent(&dev->kobj, KOBJ_ONLINE);

}



int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)

{

	int cpu, ret = 0;



	cpu_maps_update_begin();

	for_each_online_cpu(cpu) {

		if (topology_is_primary_thread(cpu))

			continue;

		ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);

		if (ret)

			break;

		/*

		 * As this needs to hold the cpu maps lock it's impossible

		 * to call device_offline() because that ends up calling

		 * cpu_down() which takes cpu maps lock. cpu maps lock

		 * needs to be held as this might race against in kernel

		 * abusers of the hotplug machinery (thermal management).

		 *

		 * So nothing would update device:offline state. That would

		 * leave the sysfs entry stale and prevent onlining after

		 * smt control has been changed to 'off' again. This is

		 * called under the sysfs hotplug lock, so it is properly

		 * serialized against the regular offline usage.

		 */

		cpuhp_offline_cpu_device(cpu);

	}

	if (!ret)

		cpu_smt_control = ctrlval;

	cpu_maps_update_done();

	return ret;

}



int cpuhp_smt_enable(void)

{

	int cpu, ret = 0;



	cpu_maps_update_begin();

	cpu_smt_control = CPU_SMT_ENABLED;

	for_each_present_cpu(cpu) {

		/* Skip online CPUs and CPUs on offline nodes */

		if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))

			continue;

		ret = _cpu_up(cpu, 0, CPUHP_ONLINE);

		if (ret)

			break;

		/* See comment in cpuhp_smt_disable() */

		cpuhp_online_cpu_device(cpu);

	}

	cpu_maps_update_done();

	return ret;

}

#endif



#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)

static ssize_t show_cpuhp_state(struct device *dev,

				struct device_attribute *attr, char *buf)
@@ -2063,77 +2135,6 @@ static const struct attribute_group cpuhp_cpu_root_attr_group = { 


#ifdef CONFIG_HOTPLUG_SMT



static void cpuhp_offline_cpu_device(unsigned int cpu)

{

	struct device *dev = get_cpu_device(cpu);



	dev->offline = true;

	/* Tell user space about the state change */

	kobject_uevent(&dev->kobj, KOBJ_OFFLINE);

}



static void cpuhp_online_cpu_device(unsigned int cpu)

{

	struct device *dev = get_cpu_device(cpu);



	dev->offline = false;

	/* Tell user space about the state change */

	kobject_uevent(&dev->kobj, KOBJ_ONLINE);

}



int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)

{

	int cpu, ret = 0;



	cpu_maps_update_begin();

	for_each_online_cpu(cpu) {

		if (topology_is_primary_thread(cpu))

			continue;

		ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);

		if (ret)

			break;

		/*

		 * As this needs to hold the cpu maps lock it's impossible

		 * to call device_offline() because that ends up calling

		 * cpu_down() which takes cpu maps lock. cpu maps lock

		 * needs to be held as this might race against in kernel

		 * abusers of the hotplug machinery (thermal management).

		 *

		 * So nothing would update device:offline state. That would

		 * leave the sysfs entry stale and prevent onlining after

		 * smt control has been changed to 'off' again. This is

		 * called under the sysfs hotplug lock, so it is properly

		 * serialized against the regular offline usage.

		 */

		cpuhp_offline_cpu_device(cpu);

	}

	if (!ret)

		cpu_smt_control = ctrlval;

	cpu_maps_update_done();

	return ret;

}



int cpuhp_smt_enable(void)

{

	int cpu, ret = 0;



	cpu_maps_update_begin();

	cpu_smt_control = CPU_SMT_ENABLED;

	for_each_present_cpu(cpu) {

		/* Skip online CPUs and CPUs on offline nodes */

		if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))

			continue;

		ret = _cpu_up(cpu, 0, CPUHP_ONLINE);

		if (ret)

			break;

		/* See comment in cpuhp_smt_disable() */

		cpuhp_online_cpu_device(cpu);

	}

	cpu_maps_update_done();

	return ret;

}





static ssize_t

__store_smt_control(struct device *dev, struct device_attribute *attr,

		    const char *buf, size_t count)

CRA Git | Maintained and supported by SUSTech CRA and CCSE