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-rw-r--r--drivers/acpi/processor_driver.c14
-rw-r--r--kernel/cpu.c8
2 files changed, 19 insertions, 3 deletions
diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
index bd4e5dca3ff7..a4352b88a331 100644
--- a/drivers/acpi/processor_driver.c
+++ b/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
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 42bd331ee0ab..f45657f1eb8e 100644
--- a/kernel/cpu.c
+++ b/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);