cpu/hotplug: Hide cpu_up/down()

Use separate functions for the device core to bring a CPU up and down.

Users outside the device core must use add/remove_cpu() which will take
care of extra housekeeping work like keeping sysfs in sync.

Make cpu_up/down() static and replace the extra layer of indirection.

[ tglx: Removed the extra wrapper functions and adjusted function names ]

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200323135110.30522-18-qais.yousef@arm.com

drivers/base/cpu.c

@@ -55,7 +55,7 @@ static int cpu_subsys_online(struct device *dev)
 	if (from_nid == NUMA_NO_NODE)
 		return -ENODEV;
 
-	ret = cpu_up(cpuid);
+	ret = cpu_device_up(dev);
 	/*
 	 * When hot adding memory to memoryless node and enabling a cpu
 	 * on the node, node number of the cpu may internally change.
@@ -69,7 +69,7 @@ static int cpu_subsys_online(struct device *dev)
 
 static int cpu_subsys_offline(struct device *dev)
 {
-	return cpu_down(dev->id);
+	return cpu_device_down(dev);
 }
 
 void unregister_cpu(struct cpu *cpu)

include/linux/cpu.h

@@ -88,8 +88,8 @@ 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);
+int cpu_device_up(struct device *dev);
 void notify_cpu_starting(unsigned int cpu);
 extern void cpu_maps_update_begin(void);
 extern void cpu_maps_update_done(void);
@@ -120,8 +120,8 @@ extern void lockdep_assert_cpus_held(void);
 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);
+int cpu_device_down(struct device *dev);
 extern void smp_shutdown_nonboot_cpus(unsigned int primary_cpu);
 
 #else /* CONFIG_HOTPLUG_CPU */

kernel/cpu.c

@@ -1041,7 +1041,7 @@ static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
 	return _cpu_down(cpu, 0, target);
 }
 
-static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
+static int cpu_down(unsigned int cpu, enum cpuhp_state target)
 {
 	int err;
 
@@ -1051,11 +1051,18 @@ static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
 	return err;
 }
 
-int cpu_down(unsigned int cpu)
+/**
+ * cpu_device_down - Bring down a cpu device
+ * @dev: Pointer to the cpu device to offline
+ *
+ * This function is meant to be used by device core cpu subsystem only.
+ *
+ * Other subsystems should use remove_cpu() instead.
+ */
+int cpu_device_down(struct device *dev)
 {
-	return do_cpu_down(cpu, CPUHP_OFFLINE);
+	return cpu_down(dev->id, CPUHP_OFFLINE);
 }
-EXPORT_SYMBOL(cpu_down);
 
 int remove_cpu(unsigned int cpu)
 {
@@ -1178,8 +1185,8 @@ static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
 	}
 
 	/*
-	 * The caller of do_cpu_up might have raced with another
+	 * The caller of cpu_up() might have raced with another
-	 * caller. Ignore it for now.
+	 * caller. Nothing to do.
 	 */
 	if (st->state >= target)
 		goto out;
@@ -1223,7 +1230,7 @@ out:
 	return ret;
 }
 
-static int do_cpu_up(unsigned int cpu, enum cpuhp_state target)
+static int cpu_up(unsigned int cpu, enum cpuhp_state target)
 {
 	int err = 0;
 
@@ -1257,11 +1264,18 @@ out:
 	return err;
 }
 
-int cpu_up(unsigned int cpu)
+/**
+ * cpu_device_up - Bring up a cpu device
+ * @dev: Pointer to the cpu device to online
+ *
+ * This function is meant to be used by device core cpu subsystem only.
+ *
+ * Other subsystems should use add_cpu() instead.
+ */
+int cpu_device_up(struct device *dev)
 {
-	return do_cpu_up(cpu, CPUHP_ONLINE);
+	return cpu_up(dev->id, CPUHP_ONLINE);
 }
-EXPORT_SYMBOL_GPL(cpu_up);
 
 int add_cpu(unsigned int cpu)
 {
@@ -1289,7 +1303,7 @@ int bringup_hibernate_cpu(unsigned int sleep_cpu)
 
 	if (!cpu_online(sleep_cpu)) {
 		pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
-		ret = cpu_up(sleep_cpu);
+		ret = cpu_up(sleep_cpu, CPUHP_ONLINE);
 		if (ret) {
 			pr_err("Failed to bring hibernate-CPU up!\n");
 			return ret;
@@ -1306,7 +1320,7 @@ void bringup_nonboot_cpus(unsigned int setup_max_cpus)
 		if (num_online_cpus() >= setup_max_cpus)
 			break;
 		if (!cpu_online(cpu))
-			cpu_up(cpu);
+			cpu_up(cpu, CPUHP_ONLINE);
 	}
 }
 
@@ -2129,9 +2143,9 @@ static ssize_t write_cpuhp_target(struct device *dev,
 		goto out;
 
 	if (st->state < target)
-		ret = do_cpu_up(dev->id, target);
+		ret = cpu_up(dev->id, target);
 	else
-		ret = do_cpu_down(dev->id, target);
+		ret = cpu_down(dev->id, target);
 out:
 	unlock_device_hotplug();
 	return ret ? ret : count;