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net: core: netlink: add helper refcount dec and lock function 

Rtnl lock is encapsulated in netlink and cannot be accessed by other
modules directly. This means that reference counted objects that rely on
rtnl lock cannot use it with refcounter helper function that atomically
releases decrements reference and obtains mutex.

This patch implements simple wrapper function around refcount_dec_and_lock
that obtains rtnl lock if reference counter value reached 0.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Vlad Buslov 2018-09-24 19:22:49 +03:00 committed by David S. Miller
parent c774973e91
commit 6f99528e97
2 changed files with 8 additions and 0 deletions
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2
include/linux/rtnetlink.h
View File

@ -6,6 +6,7 @@
#include <linux/mutex.h>
#include <linux/netdevice.h>
#include <linux/wait.h>
#include <linux/refcount.h>
#include <uapi/linux/rtnetlink.h>
extern int rtnetlink_send(struct sk_buff *skb, struct net *net, u32 pid, u32 group, int echo);
@ -34,6 +35,7 @@ extern void rtnl_unlock(void);
extern int rtnl_trylock(void);
extern int rtnl_is_locked(void);
extern int rtnl_lock_killable(void);
extern bool refcount_dec_and_rtnl_lock(refcount_t *r);
extern wait_queue_head_t netdev_unregistering_wq;
extern struct rw_semaphore pernet_ops_rwsem;

6
net/core/rtnetlink.c
View File

@ -130,6 +130,12 @@ int rtnl_is_locked(void)
}
EXPORT_SYMBOL(rtnl_is_locked);
bool refcount_dec_and_rtnl_lock(refcount_t *r)
{
return refcount_dec_and_mutex_lock(r, &rtnl_mutex);
}
EXPORT_SYMBOL(refcount_dec_and_rtnl_lock);
#ifdef CONFIG_PROVE_LOCKING
bool lockdep_rtnl_is_held(void)
{