ACPICA: Add a lock to the internal object reference count mechanism

Certain external interfaces need to update object references
without holding the interpreter or namespace mutex objects. To
prevent race conditions, add a spinlock around the increment
and decrement of the reference counts for internal ACPI
objects. Reported by Andriy Gapon (avg@FreeBSD.org).

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Andriy Gapon <avg@FreeBSD.org>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpica/utmutex.c

@@ -81,7 +81,7 @@ acpi_status acpi_ut_mutex_initialize(void)
 		}
 	}
 
-	/* Create the spinlocks for use at interrupt level */
+	/* Create the spinlocks for use at interrupt level or for speed */
 
 	status = acpi_os_create_lock (&acpi_gbl_gpe_lock);
 	if (ACPI_FAILURE (status)) {
@@ -93,7 +93,13 @@ acpi_status acpi_ut_mutex_initialize(void)
 		return_ACPI_STATUS (status);
 	}
 
+	status = acpi_os_create_lock(&acpi_gbl_reference_count_lock);
+	if (ACPI_FAILURE(status)) {
+		return_ACPI_STATUS(status);
+	}
+
 	/* Mutex for _OSI support */
+
 	status = acpi_os_create_mutex(&acpi_gbl_osi_mutex);
 	if (ACPI_FAILURE(status)) {
 		return_ACPI_STATUS(status);
@@ -136,6 +142,7 @@ void acpi_ut_mutex_terminate(void)
 
 	acpi_os_delete_lock(acpi_gbl_gpe_lock);
 	acpi_os_delete_lock(acpi_gbl_hardware_lock);
+	acpi_os_delete_lock(acpi_gbl_reference_count_lock);
 
 	/* Delete the reader/writer lock */