---

yaml
---
r: 336668
b: refs/heads/master
c: 5e5041f
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 73d4511a5f1e208399b2f7a058b73578c1977611
+refs/heads/master: 5e5041f3527b36b58e864886ba34c179ad40ff92

trunk/drivers/acpi/processor_driver.c

@@ -852,8 +852,22 @@ static int acpi_processor_handle_eject(struct acpi_processor *pr)
 	if (cpu_online(pr->id))
 		cpu_down(pr->id);
 
+	get_online_cpus();
+	/*
+	 * The cpu might become online again at this point. So we check whether
+	 * the cpu has been onlined or not. If the cpu became online, it means
+	 * that someone wants to use the cpu. So acpi_processor_handle_eject()
+	 * returns -EAGAIN.
+	 */
+	if (unlikely(cpu_online(pr->id))) {
+		put_online_cpus();
+		pr_warn("Failed to remove CPU %d, because other task "
+			"brought the CPU back online\n", pr->id);
+		return -EAGAIN;
+	}
 	arch_unregister_cpu(pr->id);
 	acpi_unmap_lsapic(pr->id);
+	put_online_cpus();
 	return (0);
 }
 #else

trunk/kernel/cpu.c

@@ -348,11 +348,13 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
 	unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
 	struct task_struct *idle;
 
-	if (cpu_online(cpu) || !cpu_present(cpu))
-		return -EINVAL;
-
 	cpu_hotplug_begin();
 
+	if (cpu_online(cpu) || !cpu_present(cpu)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
 	idle = idle_thread_get(cpu);
 	if (IS_ERR(idle)) {
 		ret = PTR_ERR(idle);