[PATCH] rcu in bpqether driver.
From Suzanne Wood <suzannew@cs.pdx.edu>:
Clarify RCU implementation in bpqether.c.
Because bpq_new_device() calls list_add_rcu() and bpq_free_device() calls
list_del_rcu(), substitute list_for_each_entry_rcu() for
list_for_each_entry() in bpq_get_ax25_dev() and in bpq_seq_start().
Add rcu dereference protection in bpq_seq_next().
The rcu_read_lock()/unlock() in bpq_device_event() are removed because
netdev event handlers are called with RTNL locking in place.
FYI: bpq_free_device() calls list_del_rcu() which, per list.h, requires
synchronize_rcu() which can block or call_rcu() or call_rcu_bh() which
cannot block. Herbert Xu notes that synchronization is done here by
unregister_netdevice(). This calls synchronize_net() which in turn uses
synchronize_rcu().
Signed-off-by: Ralf Baechle DL5RB <ralf@linux-mips.org>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>
diff --git a/drivers/net/hamradio/bpqether.c b/drivers/net/hamradio/bpqether.c
index 1756f0e..cb43a9d 100644
--- a/drivers/net/hamradio/bpqether.c
+++ b/drivers/net/hamradio/bpqether.c
@@ -144,7 +144,7 @@
{
struct bpqdev *bpq;
- list_for_each_entry(bpq, &bpq_devices, bpq_list) {
+ list_for_each_entry_rcu(bpq, &bpq_devices, bpq_list) {
if (bpq->ethdev == dev)
return bpq->axdev;
}
@@ -399,7 +399,7 @@
if (*pos == 0)
return SEQ_START_TOKEN;
- list_for_each_entry(bpqdev, &bpq_devices, bpq_list) {
+ list_for_each_entry_rcu(bpqdev, &bpq_devices, bpq_list) {
if (i == *pos)
return bpqdev;
}
@@ -418,7 +418,7 @@
p = ((struct bpqdev *)v)->bpq_list.next;
return (p == &bpq_devices) ? NULL
- : list_entry(p, struct bpqdev, bpq_list);
+ : rcu_dereference(list_entry(p, struct bpqdev, bpq_list));
}
static void bpq_seq_stop(struct seq_file *seq, void *v)
@@ -561,8 +561,6 @@
if (!dev_is_ethdev(dev))
return NOTIFY_DONE;
- rcu_read_lock();
-
switch (event) {
case NETDEV_UP: /* new ethernet device -> new BPQ interface */
if (bpq_get_ax25_dev(dev) == NULL)
@@ -581,7 +579,6 @@
default:
break;
}
- rcu_read_unlock();
return NOTIFY_DONE;
}