Hm, this is indeed one step further, than i thought :-)
Thanks for this nifty solution!
I will doublecheck your suggestion with Urs and then we'll change it in
our next patch update (after some more feedback on this mailing list).
Additional feedback is welcome.
Tnx & best regards,
Oliver
Paul E. McKenney wrote:
On Fri, May 18, 2007 at 11:19:01AM +0200, Oliver Hartkopp wrote:
Hi Urs, Hello Paul,
i assume Paul refers to the can_rx_delete_all() function that adds each
receive list entry for rcu removal using the can_rx_delete RCU callback,
right?
So the idea would be to create a second RCU callback - e.g.
can_rx_delete_list() - that removes the complete list inside the RCU
callback?!?
The list removal would therefore be processed inside this new
can_rx_delete_list() in RCU context and not inside can_rx_delete_all().
@Paul: Was this your intention?
My intention was that the list-removing be placed into can_rcv_lists_delete(),
perhaps as follows:
static void can_rx_delete_all(struct hlist_head *rl)
{
struct receiver *r;
struct hlist_node *n;
hlist_for_each_entry(r, n, rl, list) {
hlist_del(&r->list);
kmem_cache_free(rcv_cache, r);
}
}
static void can_rcv_lists_delete(struct rcu_head *rp)
{
struct dev_rcv_lists *d = container_of(rp, struct dev_rcv_lists, rcu);
/* remove all receivers hooked at this netdevice */
can_rx_delete_all(&d->rx_err);
can_rx_delete_all(&d->rx_all);
can_rx_delete_all(&d->rx_fil);
can_rx_delete_all(&d->rx_inv);
can_rx_delete_all(&d->rx_eff);
for (i = 0; i < 2048; i++)
can_rx_delete_all(&d->rx_sff[i]);
kfree(d);
}
Then the code in can_notifier() can reduce to the following:
if (d) {
hlist_del_rcu(&d->list);
/* used to be a string of can_rx_delete_all(). */
} else
printk(KERN_ERR "can: notifier: receive list not "
"found for dev %s\n", dev->name);
spin_lock_bh(&rcv_lists_lock);
if (d) {
call_rcu(&d->rcu, can_rcv_lists_delete);
}
This moves the traversal work into the callback function. This is not
a problem for CONFIG_PREEMPT_RT and non-CONFIG_PREEMPT, but not sure
about CONFIG_PREEMPT.
But it sure has the potential to cut down on a bunch of call_rcu()
work...
Thanx, Paul
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