PM: hibernate: Avoid missing wakeup events during hibernation

Wakeup events that occur in the hibernation process's
hibernation_platform_enter() cannot wake up the system. Although the
current hibernation framework will execute part of the recovery process
after a wakeup event occurs, it ultimately performs a shutdown operation
because the system does not check the return value of
hibernation_platform_enter(). In short, if a wakeup event occurs before
putting the system into the final low-power state, it will be missed.

To solve this problem, check the return value of
hibernation_platform_enter(). When it returns -EAGAIN or -EBUSY (indicate
the occurrence of a wakeup event), execute the hibernation recovery
process, discard the previously saved image, and ultimately return to the
working state.
Signed-off-by: Chris Feng <chris.feng@mediatek.com>
[ rjw: Rephrase the message printed when going back to the working state ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

kernel/power/hibernate.c

@@ -642,9 +642,9 @@ int hibernation_platform_enter(void)
  */
 static void power_down(void)
 {
-#ifdef CONFIG_SUSPEND
 	int error;
 
+#ifdef CONFIG_SUSPEND
 	if (hibernation_mode == HIBERNATION_SUSPEND) {
 		error = suspend_devices_and_enter(mem_sleep_current);
 		if (error) {
@@ -667,7 +667,13 @@ static void power_down(void)
 		kernel_restart(NULL);
 		break;
 	case HIBERNATION_PLATFORM:
-		hibernation_platform_enter();
+		error = hibernation_platform_enter();
+		if (error == -EAGAIN || error == -EBUSY) {
+			swsusp_unmark();
+			events_check_enabled = false;
+			pr_info("Wakeup event detected during hibernation, rolling back.\n");
+			return;
+		}
 		fallthrough;
 	case HIBERNATION_SHUTDOWN:
 		if (kernel_can_power_off())

kernel/power/power.h

@@ -175,6 +175,8 @@ extern int swsusp_write(unsigned int flags);
 void swsusp_close(void);
 #ifdef CONFIG_SUSPEND
 extern int swsusp_unmark(void);
+#else
+static inline int swsusp_unmark(void) { return 0; }
 #endif
 
 struct __kernel_old_timeval;