Hibernation: Make sure that ACPI is enabled in acpi_hibernation_finish

If the BIOS does not enable ACPI and the "acpi=off" command line parameter
is passed to the boot kernel, ACPI may be disabled when the (restored)
image kernel attempts to execute acpi_hibernation_finish().  To prevent
this from happening we can call acpi_enable() from
acpi_hibernation_finish() (if ACPI is already enabled, this will have no
effect).

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/sleep/main.c

@@ -256,6 +256,11 @@ static int acpi_hibernation_enter(void)
 
 static void acpi_hibernation_finish(void)
 {
+	/*
+	 * If ACPI is not enabled by the BIOS and the boot kernel, we need to
+	 * enable it here.
+	 */
+	acpi_enable();
 	acpi_leave_sleep_state(ACPI_STATE_S4);
 	acpi_disable_wakeup_device(ACPI_STATE_S4);