ACPICA: Update comments for acquire/release mutex interfaces

pdate comments for acquire/release mutex interfaces

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Alexey Starikovskiy <astarikovskiy@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 30 insertions, 6 deletions

diff --git a/drivers/acpi/executer/exmutex.c b/drivers/acpi/executer/exmutex.c
index 0bebe751aac5..32f24a8fba57 100644
--- a/drivers/acpi/executer/exmutex.c
+++ b/drivers/acpi/executer/exmutex.c
@@ -134,7 +134,16 @@ acpi_ex_link_mutex(union acpi_operand_object *obj_desc,
  *
  * RETURN:      Status
  *
- * DESCRIPTION: Acquire an AML mutex, low-level interface
+ * DESCRIPTION: Acquire an AML mutex, low-level interface. Provides a common
+ *              path that supports multiple acquires by the same thread.
+ *
+ * MUTEX:       Interpreter must be locked
+ *
+ * NOTE: This interface is called from three places:
+ * 1) From acpi_ex_acquire_mutex, via an AML Acquire() operator
+ * 2) From acpi_ex_acquire_global_lock when an AML Field access requires the
+ *    global lock
+ * 3) From the external interface, acpi_acquire_global_lock
  *
  ******************************************************************************/
 
@@ -174,7 +183,7 @@ acpi_ex_acquire_mutex_object(u16 timeout,
                 return_ACPI_STATUS(status);
         }
 
-        /* Have the mutex: update mutex and save the sync_level */
+        /* Acquired the mutex: update mutex object */
 
         obj_desc->mutex.thread_id = thread_id;
         obj_desc->mutex.acquisition_depth = 1;
@@ -211,7 +220,7 @@ acpi_ex_acquire_mutex(union acpi_operand_object *time_desc,
                 return_ACPI_STATUS(AE_BAD_PARAMETER);
         }
 
-        /* Sanity check: we must have a valid thread ID */
+        /* Must have a valid thread ID */
 
         if (!walk_state->thread) {
                 ACPI_ERROR((AE_INFO,
@@ -221,7 +230,7 @@ acpi_ex_acquire_mutex(union acpi_operand_object *time_desc,
         }
 
         /*
-         * Current Sync level must be less than or equal to the sync level of the
+         * Current sync level must be less than or equal to the sync level of the
          * mutex. This mechanism provides some deadlock prevention
          */
         if (walk_state->thread->current_sync_level > obj_desc->mutex.sync_level) {
@@ -236,6 +245,9 @@ acpi_ex_acquire_mutex(union acpi_operand_object *time_desc,
                                               obj_desc,
                                               walk_state->thread->thread_id);
         if (ACPI_SUCCESS(status) && obj_desc->mutex.acquisition_depth == 1) {
+
+                /* Save Thread object, original/current sync levels */
+
                 obj_desc->mutex.owner_thread = walk_state->thread;
                 obj_desc->mutex.original_sync_level =
                     walk_state->thread->current_sync_level;
@@ -259,6 +271,16 @@ acpi_ex_acquire_mutex(union acpi_operand_object *time_desc,
  * RETURN:      Status
  *
  * DESCRIPTION: Release a previously acquired Mutex, low level interface.
+ *              Provides a common path that supports multiple releases (after
+ *              previous multiple acquires) by the same thread.
+ *
+ * MUTEX:       Interpreter must be locked
+ *
+ * NOTE: This interface is called from three places:
+ * 1) From acpi_ex_release_mutex, via an AML Acquire() operator
+ * 2) From acpi_ex_release_global_lock when an AML Field access requires the
+ *    global lock
+ * 3) From the external interface, acpi_release_global_lock
  *
  ******************************************************************************/
 
@@ -294,6 +316,8 @@ acpi_status acpi_ex_release_mutex_object(union acpi_operand_object *obj_desc)
                 acpi_os_release_mutex(obj_desc->mutex.os_mutex);
         }
 
+        /* Clear mutex info */
+
         obj_desc->mutex.thread_id = 0;
         return_ACPI_STATUS(status);
 }
@@ -348,7 +372,7 @@ acpi_ex_release_mutex(union acpi_operand_object *obj_desc,
                 return_ACPI_STATUS(AE_AML_NOT_OWNER);
         }
 
-        /* Sanity check: we must have a valid thread ID */
+        /* Must have a valid thread ID */
 
         if (!walk_state->thread) {
                 ACPI_ERROR((AE_INFO,
@@ -370,7 +394,7 @@ acpi_ex_release_mutex(union acpi_operand_object *obj_desc,
 
         status = acpi_ex_release_mutex_object(obj_desc);
 
-        /* Restore sync_level */
+        /* Restore the original sync_level */
 
         walk_state->thread->current_sync_level =
             obj_desc->mutex.original_sync_level;