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sysctl: Initial support for auto-unregistering sysctl tables.

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Add nreg to ctl_table_header.  When nreg drops to 0 the ctl_table_header
will be unregistered.

Factor out drop_sysctl_table from unregister_sysctl_table, and add
the logic for decrementing nreg.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2012-01-09 17:24:30 -08:00
parent 3cc3e04636
commit 938aaa4f92
2 changed files with 20 additions and 9 deletions
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28
fs/proc/proc_sysctl.c
View File

@ -29,8 +29,9 @@ static struct ctl_table root_table[1];
static struct ctl_table_root sysctl_table_root;
static struct ctl_table_header root_table_header = {
{{.count = 1,
.ctl_table = root_table,
.ctl_entry = LIST_HEAD_INIT(sysctl_table_root.default_set.list),}},
.nreg = 1,
.ctl_table = root_table,
.ctl_entry = LIST_HEAD_INIT(sysctl_table_root.default_set.list),}},
.root = &sysctl_table_root,
.set = &sysctl_table_root.default_set,
};
@ -938,6 +939,7 @@ struct ctl_table_header *__register_sysctl_table(
header->unregistering = NULL;
header->root = root;
header->count = 1;
header->nreg = 1;
if (sysctl_check_table(path, table))
goto fail;
@ -1192,6 +1194,20 @@ struct ctl_table_header *register_sysctl_table(struct ctl_table *table)
}
EXPORT_SYMBOL(register_sysctl_table);
static void drop_sysctl_table(struct ctl_table_header *header)
{
if (--header->nreg)
return;
start_unregistering(header);
if (!--header->parent->count) {
WARN_ON(1);
kfree_rcu(header->parent, rcu);
}
if (!--header->count)
kfree_rcu(header, rcu);
}
/**
* unregister_sysctl_table - unregister a sysctl table hierarchy
* @header: the header returned from register_sysctl_table
@ -1224,13 +1240,7 @@ void unregister_sysctl_table(struct ctl_table_header * header)
}
spin_lock(&sysctl_lock);
start_unregistering(header);
if (!--header->parent->count) {
WARN_ON(1);
kfree_rcu(header->parent, rcu);
}
if (!--header->count)
kfree_rcu(header, rcu);
drop_sysctl_table(header);
spin_unlock(&sysctl_lock);
}
EXPORT_SYMBOL(unregister_sysctl_table);

1
include/linux/sysctl.h
View File

@ -1032,6 +1032,7 @@ struct ctl_table_header
struct list_head ctl_entry;
int used;
int count;
int nreg;
};
struct rcu_head rcu;
};