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[PATCH] rcu in bpqether driver.

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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>
This commit is contained in:
Ralf Baechle 2005-10-17 12:42:32 +01:00 committed by Jeff Garzik
parent ad4ebed00f
commit bc0a743860
1 changed files with 3 additions and 6 deletions
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9
drivers/net/hamradio/bpqether.c
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@ -144,7 +144,7 @@ static inline struct net_device *bpq_get_ax25_dev(struct net_device *dev)
{
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 @@ static void *bpq_seq_start(struct seq_file *seq, loff_t *pos)
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 @@ static void *bpq_seq_next(struct seq_file *seq, void *v, loff_t *pos)
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 @@ static int bpq_device_event(struct notifier_block *this,unsigned long event, voi
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 @@ static int bpq_device_event(struct notifier_block *this,unsigned long event, voi
default:
break;
}
rcu_read_unlock();
return NOTIFY_DONE;
}