rapidio: add lock protection for doorbell list

Add lock protection around doorbell list handling to prevent list
corruption on SMP platforms.

Signed-off-by: Alexandre Bounine <alexandre.bounine@idt.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Aurelien Jacquiot <a-jacquiot@ti.com>
Cc: Andre van Herk <andre.van.herk@prodrive-technologies.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/rio.h b/include/linux/rio.h
index f833773..948f605 100644
--- a/include/linux/rio.h
+++ b/include/linux/rio.h
@@ -248,6 +248,7 @@
  * @node: Node in global list of master ports
  * @nnode: Node in network list of master ports
  * @net: RIO net this mport is attached to
+ * @lock: lock to synchronize lists manipulations
  * @iores: I/O mem resource that this master port interface owns
  * @riores: RIO resources that this master port interfaces owns
  * @inb_msg: RIO inbound message event descriptors
@@ -271,6 +272,7 @@
 	struct list_head node;	/* node in global list of ports */
 	struct list_head nnode;	/* node in net list of ports */
 	struct rio_net *net;	/* RIO net this mport is attached to */
+	struct mutex lock;
 	struct resource iores;
 	struct resource riores[RIO_MAX_MPORT_RESOURCES];
 	struct rio_msg inb_msg[RIO_MAX_MBOX];