[1/5] Staging: batman-adv: Always synchronize rcu's on module shutdown

Message ID 1284326516-30540-2-git-send-email-sven.eckelmann@gmx.de
State Not Applicable, archived

Commit Message

Sven Eckelmann Sept. 12, 2010, 9:21 p.m. UTC
  From: Linus Lüssing <linus.luessing@web.de>

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>
 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)
 	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)
-	synchronize_net();
-	synchronize_rcu();
 	atomic_set(&bat_priv->mesh_state, MESH_INACTIVE);