if_lock
spin_lock_init(&vif->if_lock);
spinlock_t if_lock;
spin_lock_bh(&vif->if_lock);
spin_unlock_bh(&vif->if_lock);
spin_lock_bh(&vif->if_lock);
spin_unlock_bh(&vif->if_lock);
spin_lock_bh(&vif->if_lock);
spin_unlock_bh(&vif->if_lock);
if_lock(t);
#define if_lock(t) mutex_lock(&(t->if_lock))
#define if_unlock(t) mutex_unlock(&(t->if_lock))
if_lock(t);
mutex_init(&t->if_lock);
if_lock(t);
struct mutex if_lock; /* for list of devices */