IB/core: lock client data with lists_rwsem

An ib_client callback that is called with the lists_rwsem locked only for
read is protected from changes to the IB client lists, but not from
ib_unregister_device() freeing its client data. This is because
ib_unregister_device() will remove the device from the device list with
lists_rwsem locked for write, but perform the rest of the cleanup,
including the call to remove() without that lock.

Mark client data that is undergoing de-registration with a new going_down
flag in the client data context. Lock the client data list with lists_rwsem
for write in addition to using the spinlock, so that functions calling the
callback would be able to lock only lists_rwsem for read and let callbacks
sleep.

Since ib_unregister_client() now marks the client data context, no need for
remove() to search the context again, so pass the client data directly to
remove() callbacks.

Reviewed-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Haggai Eran <haggaie@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 7448a27..449609b 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -1550,6 +1550,8 @@ struct ib_device {
 
 	spinlock_t                    client_data_lock;
 	struct list_head              core_list;
+	/* Access to the client_data_list is protected by the client_data_lock
+	 * spinlock and the lists_rwsem read-write semaphore */
 	struct list_head              client_data_list;
 
 	struct ib_cache               cache;
@@ -1761,7 +1763,7 @@ struct ib_device {
 struct ib_client {
 	char  *name;
 	void (*add)   (struct ib_device *);
-	void (*remove)(struct ib_device *);
+	void (*remove)(struct ib_device *, void *client_data);
 
 	struct list_head list;
 };