From: Linus Lüssing <[email protected]> During the module shutdown procedure in batman_exit(), a rcu callback is being scheduled (batman_exit -> hardif_remove_interfaces -> hardif_remove_interfae -> call_rcu). However, when the kernel unloads the module, the rcu callback might not have been executed yet, resulting in a "unable to handle kernel paging request" in __rcu_process_callback afterwards, causing the kernel to freeze.
The synchronize_net and synchronize_rcu in mesh_free are currently called before the call_rcu in hardif_remove_interface and have no real effect on it. Therefore, we should always flush all rcu callback functions scheduled during the shutdown procedure using synchronize_net. The call to synchronize_rcu can be omitted because synchronize_net already calls it. Signed-off-by: Linus Lüssing <[email protected]> Signed-off-by: Sven Eckelmann <[email protected]> --- drivers/staging/batman-adv/main.c | 5 ++--- 1 files changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/staging/batman-adv/main.c b/drivers/staging/batman-adv/main.c index 498861f..b3e23e1 100644 --- a/drivers/staging/batman-adv/main.c +++ b/drivers/staging/batman-adv/main.c @@ -71,6 +71,8 @@ static void __exit batman_exit(void) flush_workqueue(bat_event_workqueue); destroy_workqueue(bat_event_workqueue); bat_event_workqueue = NULL; + + synchronize_net(); } int mesh_init(struct net_device *soft_iface) @@ -132,9 +134,6 @@ void mesh_free(struct net_device *soft_iface) hna_local_free(bat_priv); hna_global_free(bat_priv); - synchronize_net(); - - synchronize_rcu(); atomic_set(&bat_priv->mesh_state, MESH_INACTIVE); } -- 1.7.2.3
