[PATCH 5/6] UML - Add locking to network transport registration

[Jeff Dike]

The registration of host network transports needed some locking.  The
transport list itself is locked, but calls to the registration
routines are not.  This is compensated for by checking that a
transport structure is not yet on any list.

I also took the opportunity to const all fields in the transport
structure except the list, which obviously can be modified.

Signed-off-by: Jeff Dike <jdike@xxxxxxxxxxx>

--
 arch/um/drivers/net_kern.c |    9 +++++----
 arch/um/include/net_kern.h |    8 ++++----
 2 files changed, 9 insertions(+), 8 deletions(-)

Index: linux-2.6.18-mm/arch/um/drivers/net_kern.c
===================================================================
--- linux-2.6.18-mm.orig/arch/um/drivers/net_kern.c	2006-12-29 12:58:59.000000000 -0500
+++ linux-2.6.18-mm/arch/um/drivers/net_kern.c	2006-12-29 12:59:19.000000000 -0500
@@ -498,10 +498,8 @@ struct eth_init {
 	int index;
 };
 
-/* Filled in at boot time.  Will need locking if the transports become
- * modular.
- */
-struct list_head transports = LIST_HEAD_INIT(transports);
+static DEFINE_SPINLOCK(transports_lock);
+static LIST_HEAD(transports);
 
 /* Filled in during early boot */
 struct list_head eth_cmd_line = LIST_HEAD_INIT(eth_cmd_line);
@@ -540,7 +538,10 @@ void register_transport(struct transport
 	char *mac = NULL;
 	int match;
 
+	spin_lock(&transports_lock);
+	BUG_ON(!list_empty(&new->list));
 	list_add(&new->list, &transports);
+	spin_unlock(&transports_lock);
 
 	list_for_each_safe(ele, next, &eth_cmd_line){
 		eth = list_entry(ele, struct eth_init, list);
Index: linux-2.6.18-mm/arch/um/include/net_kern.h
===================================================================
--- linux-2.6.18-mm.orig/arch/um/include/net_kern.h	2006-12-29 12:23:02.000000000 -0500
+++ linux-2.6.18-mm/arch/um/include/net_kern.h	2006-12-29 12:59:19.000000000 -0500
@@ -52,12 +52,12 @@ struct net_kern_info {
 
 struct transport {
 	struct list_head list;
-	char *name;
-	int (*setup)(char *, char **, void *);
+	const char *name;
+	int (* const setup)(char *, char **, void *);
 	const struct net_user_info *user;
 	const struct net_kern_info *kern;
-	int private_size;
-	int setup_size;
+	const int private_size;
+	const int setup_size;
 };
 
 extern struct net_device *ether_init(int);

-
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