So I would ack the patch with a minor change in the commit message. So instead of
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. Therefore, we should always flush all rcu callback functions scheduled during the shutdown procedure.
something like
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.
Yep, sounds good :). Thanks for reviewing and the info about synchronize_net.
Cheers, Linus
thanks, Sven