1 files changed, 82 insertions, 0 deletions

diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
index 218cdb16163c..120cee1c3f8d 100644
--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -21,6 +21,7 @@
 #include <asm/suspend.h>
 #include <asm/debugreg.h>
 #include <asm/fpu-internal.h> /* pcntxt_mask */
+#include <asm/cpu.h>
 
 #ifdef CONFIG_X86_32
 static struct saved_context saved_context;
@@ -237,3 +238,84 @@ void restore_processor_state(void)
 #ifdef CONFIG_X86_32
 EXPORT_SYMBOL(restore_processor_state);
 #endif
+
+/*
+ * When bsp_check() is called in hibernate and suspend, cpu hotplug
+ * is disabled already. So it's unnessary to handle race condition between
+ * cpumask query and cpu hotplug.
+ */
+static int bsp_check(void)
+{
+        if (cpumask_first(cpu_online_mask) != 0) {
+                pr_warn("CPU0 is offline.\n");
+                return -ENODEV;
+        }
+
+        return 0;
+}
+
+static int bsp_pm_callback(struct notifier_block *nb, unsigned long action,
+                           void *ptr)
+{
+        int ret = 0;
+
+        switch (action) {
+        case PM_SUSPEND_PREPARE:
+        case PM_HIBERNATION_PREPARE:
+                ret = bsp_check();
+                break;
+#ifdef CONFIG_DEBUG_HOTPLUG_CPU0
+        case PM_RESTORE_PREPARE:
+                /*
+                 * When system resumes from hibernation, online CPU0 because
+                 * 1. it's required for resume and
+                 * 2. the CPU was online before hibernation
+                 */
+                if (!cpu_online(0))
+                        _debug_hotplug_cpu(0, 1);
+                break;
+        case PM_POST_RESTORE:
+                /*
+                 * When a resume really happens, this code won't be called.
+                 *
+                 * This code is called only when user space hibernation software
+                 * prepares for snapshot device during boot time. So we just
+                 * call _debug_hotplug_cpu() to restore to CPU0's state prior to
+                 * preparing the snapshot device.
+                 *
+                 * This works for normal boot case in our CPU0 hotplug debug
+                 * mode, i.e. CPU0 is offline and user mode hibernation
+                 * software initializes during boot time.
+                 *
+                 * If CPU0 is online and user application accesses snapshot
+                 * device after boot time, this will offline CPU0 and user may
+                 * see different CPU0 state before and after accessing
+                 * the snapshot device. But hopefully this is not a case when
+                 * user debugging CPU0 hotplug. Even if users hit this case,
+                 * they can easily online CPU0 back.
+                 *
+                 * To simplify this debug code, we only consider normal boot
+                 * case. Otherwise we need to remember CPU0's state and restore
+                 * to that state and resolve racy conditions etc.
+                 */
+                _debug_hotplug_cpu(0, 0);
+                break;
+#endif
+        default:
+                break;
+        }
+        return notifier_from_errno(ret);
+}
+
+static int __init bsp_pm_check_init(void)
+{
+        /*
+         * Set this bsp_pm_callback as lower priority than
+         * cpu_hotplug_pm_callback. So cpu_hotplug_pm_callback will be called
+         * earlier to disable cpu hotplug before bsp online check.
+         */
+        pm_notifier(bsp_pm_callback, -INT_MAX);
+        return 0;
+}
+
+core_initcall(bsp_pm_check_init);