On Mon, Feb 11, 2008 at 08:55:41AM +0100, Frank Blaschka wrote:
> Paul E. McKenney schrieb:
> > On Fri, Feb 08, 2008 at 03:10:00PM +0100, [EMAIL PROTECTED] wrote:
> >> From: Frank Blaschka <[EMAIL PROTECTED]>
> >>
> >> List of major changes and improvements:
> >> no manipulation of the global ARP constructor
> >> clean code split into core, layer 2 and layer 3 functionality
> >> better exploitation of the ethtool interface
> >> better representation of the various hardware capabilities
> >> fix packet socket support (tcpdump), no fake_ll required
> >> osasnmpd notification via udev events
> >> coding style and beautification
> >
> > One question below...
> >
> >> Signed-off-by: Frank Blaschka <[EMAIL PROTECTED]>
> >> ---
> >
> > [ . . . ]
> >
> >> +static void qeth_l3_vlan_rx_add_vid(struct net_device *dev, unsigned
> >> short vid)
> >> +{
> >> + struct net_device *vlandev;
> >> + struct qeth_card *card = (struct qeth_card *) dev->priv;
> >> + struct in_device *in_dev;
> >> +
> >> + if (card->info.type == QETH_CARD_TYPE_IQD)
> >> + return;
> >> +
> >> + vlandev = vlan_group_get_device(card->vlangrp, vid);
> >> + vlandev->neigh_setup = qeth_l3_neigh_setup;
> >> +
> >> + in_dev = __in_dev_get_rcu(vlandev);
> >
> > Is this really in an RCU read-side critical section? Or is this just
> > using common code?
> >
> > Thanx, Paul
> > --
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> >
>
> Hi Paul,
>
> thanks for pointing at this. Using __in_dev_get_rcu without the rcu lock
> is probably a bug at this place (right?).
It would be a bug -unless- you are holding the update-side lock.
> Using in_dev_get/in_dev_put
> would be more appropriate. Same for qeth_l3_free_vlan_addresses4(), here
> we take the rcu read lock, but in_dev_get/in_dev_put would be the better
> choice. What do you think?
Ummm... "It depends." ;-)
Keeping in mind that I am not an expert on this part of the kernel, I
would guess that qeth_l3_free_vlan_addresses4() is not particularly
performance-sensitive, so I don't see any reason in_dev_get/in_dev_put
would be a problem. If it turns out that qeth_l3_free_vlan_addresses4()
is in fact performance-sensitive, then rcu_read_lock()/rcu_read_unlock()
would be a better choice.
Thanx, Paul
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