1 files changed, 35 insertions, 10 deletions

diff --git a/drivers/acpi/acpica/exmutex.c b/drivers/acpi/acpica/exmutex.c
index d301c1f363ef..2f0114202b05 100644
--- a/drivers/acpi/acpica/exmutex.c
+++ b/drivers/acpi/acpica/exmutex.c
@@ -83,6 +83,15 @@ void acpi_ex_unlink_mutex(union acpi_operand_object *obj_desc)
 
 	if (obj_desc->mutex.prev) {
 		(obj_desc->mutex.prev)->mutex.next = obj_desc->mutex.next;
+
+		/*
+		 * Migrate the previous sync level associated with this mutex to the
+		 * previous mutex on the list so that it may be preserved. This handles
+		 * the case where several mutexes have been acquired at the same level,
+		 * but are not released in opposite order.
+		 */
+		(obj_desc->mutex.prev)->mutex.original_sync_level =
+		    obj_desc->mutex.original_sync_level;
 	} else {
 		thread->acquired_mutex_list = obj_desc->mutex.next;
 	}
@@ -349,6 +358,7 @@ acpi_ex_release_mutex(union acpi_operand_object *obj_desc,
 		      struct acpi_walk_state *walk_state)
 {
 	acpi_status status = AE_OK;
+	u8 previous_sync_level;
 
 	ACPI_FUNCTION_TRACE(ex_release_mutex);
 
@@ -373,11 +383,12 @@ acpi_ex_release_mutex(union acpi_operand_object *obj_desc,
 	     walk_state->thread->thread_id)
 	    && (obj_desc != acpi_gbl_global_lock_mutex)) {
 		ACPI_ERROR((AE_INFO,
-			    "Thread %lX cannot release Mutex [%4.4s] acquired by thread %lX",
-			    (unsigned long)walk_state->thread->thread_id,
+			    "Thread %p cannot release Mutex [%4.4s] acquired by thread %p",
+			    ACPI_CAST_PTR(void, walk_state->thread->thread_id),
 			    acpi_ut_get_node_name(obj_desc->mutex.node),
-			    (unsigned long)obj_desc->mutex.owner_thread->
-			    thread_id));
+			    ACPI_CAST_PTR(void,
+					  obj_desc->mutex.owner_thread->
+					  thread_id)));
 		return_ACPI_STATUS(AE_AML_NOT_OWNER);
 	}
 
@@ -391,10 +402,14 @@ acpi_ex_release_mutex(union acpi_operand_object *obj_desc,
 	}
 
 	/*
-	 * The sync level of the mutex must be less than or equal to the current
-	 * sync level
+	 * The sync level of the mutex must be equal to the current sync level. In
+	 * other words, the current level means that at least one mutex at that
+	 * level is currently being held. Attempting to release a mutex of a
+	 * different level can only mean that the mutex ordering rule is being
+	 * violated. This behavior is clarified in ACPI 4.0 specification.
 	 */
-	if (obj_desc->mutex.sync_level > walk_state->thread->current_sync_level) {
+	if (obj_desc->mutex.sync_level !=
+	    walk_state->thread->current_sync_level) {
 		ACPI_ERROR((AE_INFO,
 			    "Cannot release Mutex [%4.4s], SyncLevel mismatch: mutex %d current %d",
 			    acpi_ut_get_node_name(obj_desc->mutex.node),
@@ -403,14 +418,24 @@ acpi_ex_release_mutex(union acpi_operand_object *obj_desc,
 		return_ACPI_STATUS(AE_AML_MUTEX_ORDER);
 	}
 
+	/*
+	 * Get the previous sync_level from the head of the acquired mutex list.
+	 * This handles the case where several mutexes at the same level have been
+	 * acquired, but are not released in reverse order.
+	 */
+	previous_sync_level =
+	    walk_state->thread->acquired_mutex_list->mutex.original_sync_level;
+
 	status = acpi_ex_release_mutex_object(obj_desc);
+	if (ACPI_FAILURE(status)) {
+		return_ACPI_STATUS(status);
+	}
 
 	if (obj_desc->mutex.acquisition_depth == 0) {
 
-		/* Restore the original sync_level */
+		/* Restore the previous sync_level */
 
-		walk_state->thread->current_sync_level =
-		    obj_desc->mutex.original_sync_level;
+		walk_state->thread->current_sync_level = previous_sync_level;
 	}
 	return_ACPI_STATUS(status);
 }