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configfs: Convert subsystem semaphore to mutex

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Convert the su_sem member of struct configfs_subsystem to a struct
mutex, as that's what it is. Also convert all the users and update
Documentation/configfs.txt and Documentation/configfs_example.c
accordingly.

[ Conflict in fs/dlm/config.c with commit
  3168b0780d manually resolved. --Mark ]

Inspired-by: Satyam Sharma <[email protected]>
Signed-off-by: Joel Becker <[email protected]>
Signed-off-by: Mark Fasheh <[email protected]>
This commit is contained in:
Joel Becker 2007-07-06 23:33:17 -07:00 • committed by Mark Fasheh
commit e6bd07aee7
6 changed files with 26 additions and 26 deletions
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18
Documentation/filesystems/configfs/configfs.txt
View file

@ -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)]

2
Documentation/filesystems/configfs/configfs_example.c
View file

@ -453,7 +453,7 @@ static int __init configfs_example_init(void)
subsys = example_subsys[i];
config_group_init(&subsys->su_group);
init_MUTEX(&subsys->su_sem);
mutex_init(&subsys->su_mutex);
ret = configfs_register_subsystem(subsys);
if (ret) {
printk(KERN_ERR "Error %d while registering subsystem %s\n",