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Staging: batman-adv: Always synchronize rcu's on module shutdown

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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 <linus.luessing@web.de>
Signed-off-by: Sven Eckelmann <sven.eckelmann@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Linus Lüssing 2010-09-12 23:21:52 +02:00 committed by Greg Kroah-Hartman
parent 6267ea655f
commit 09686b560f
1 changed files with 2 additions and 3 deletions
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5
drivers/staging/batman-adv/main.c
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@ -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);
}