Hi Sven,
synchronize_net already contains a synchronize_rcu at its end, so the synchronize_rcu in the batman code there has always been redundant.
I've removed the synchronize_rcu instead of the synchronize_net to be on the safe side. I guess usually no more packets should arrive anyway as the batman packet type is not registered anymore. But I wasn't sure if the might_sleep() of synchronize_net() might be needed for something, so I didn't dare to remove synchronize_net.
If someone says it'd be ok to remove synchronize_net() instead, I could make a new patch, no problem.
Cheers, Linus
On Mon, Sep 06, 2010 at 09:30:46AM +0200, Sven Eckelmann wrote:
On Mon, Sep 06, 2010 at 01:29:53AM +0200, Linus Lüssing wrote:
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.
I am really irritated by your patch. I would have expected that you add a synchronyze_rcu in batman_exit and that was it. Instead I see a synchronize_net added and a synchronize_net/-_rcu removed from mesh_free. This doesn't seem to match at all. Could you please explain further why it is implemented that way?
thanks, Sven