diff options
Diffstat (limited to 'Documentation/filesystems/configfs/configfs.txt')
| -rw-r--r-- | Documentation/filesystems/configfs/configfs.txt | 18 |
1 files changed, 9 insertions, 9 deletions
diff --git a/Documentation/filesystems/configfs/configfs.txt b/Documentation/filesystems/configfs/configfs.txt index b34cdb50eab..21f038e6672 100644 --- a/Documentation/filesystems/configfs/configfs.txt +++ b/Documentation/filesystems/configfs/configfs.txt @@ -280,18 +280,18 @@ tells configfs to make the subsystem appear in the file tree. struct configfs_subsystem { struct config_group su_group; - struct semaphore su_sem; + struct mutex su_mutex; }; int configfs_register_subsystem(struct configfs_subsystem *subsys); void configfs_unregister_subsystem(struct configfs_subsystem *subsys); - A subsystem consists of a toplevel config_group and a semaphore. + A subsystem consists of a toplevel config_group and a mutex. The group is where child config_items are created. For a subsystem, this group is usually defined statically. Before calling configfs_register_subsystem(), the subsystem must have initialized the group via the usual group _init() functions, and it must also have -initialized the semaphore. +initialized the mutex. When the register call returns, the subsystem is live, and it will be visible via configfs. At that point, mkdir(2) can be called and the subsystem must be ready for it. @@ -303,7 +303,7 @@ subsystem/group and the simple_child item in configfs_example.c It shows a trivial object displaying and storing an attribute, and a simple group creating and destroying these children. -[Hierarchy Navigation and the Subsystem Semaphore] +[Hierarchy Navigation and the Subsystem Mutex] There is an extra bonus that configfs provides. The config_groups and config_items are arranged in a hierarchy due to the fact that they @@ -314,19 +314,19 @@ and config_item->ci_parent structure members. A subsystem can navigate the cg_children list and the ci_parent pointer to see the tree created by the subsystem. This can race with configfs' -management of the hierarchy, so configfs uses the subsystem semaphore to +management of the hierarchy, so configfs uses the subsystem mutex to protect modifications. Whenever a subsystem wants to navigate the hierarchy, it must do so under the protection of the subsystem -semaphore. +mutex. -A subsystem will be prevented from acquiring the semaphore while a newly +A subsystem will be prevented from acquiring the mutex while a newly allocated item has not been linked into this hierarchy. Similarly, it -will not be able to acquire the semaphore while a dropping item has not +will not be able to acquire the mutex while a dropping item has not yet been unlinked. This means that an item's ci_parent pointer will never be NULL while the item is in configfs, and that an item will only be in its parent's cg_children list for the same duration. This allows a subsystem to trust ci_parent and cg_children while they hold the -semaphore. +mutex. [Item Aggregation Via symlink(2)] |