* [PATCH] inetpeer: Don't disable BH for initial fast RCU lookup.
@ 2011-03-08 22:59 David Miller
2011-03-13 10:04 ` Eric Dumazet
0 siblings, 1 reply; 5+ messages in thread
From: David Miller @ 2011-03-08 22:59 UTC (permalink / raw)
To: netdev; +Cc: eric.dumazet
If modifications on other cpus are ok, then modifications to
the tree during lookup done by the local cpu are ok too.
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/ipv4/inetpeer.c | 18 +++++++++---------
1 files changed, 9 insertions(+), 9 deletions(-)
diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index f604ffd..6442c35 100644
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -206,16 +206,16 @@ static int addr_compare(const struct inetpeer_addr *a,
})
/*
- * Called with rcu_read_lock_bh()
+ * Called with rcu_read_lock()
* Because we hold no lock against a writer, its quite possible we fall
* in an endless loop.
* But every pointer we follow is guaranteed to be valid thanks to RCU.
* We exit from this function if number of links exceeds PEER_MAXDEPTH
*/
-static struct inet_peer *lookup_rcu_bh(const struct inetpeer_addr *daddr,
- struct inet_peer_base *base)
+static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr,
+ struct inet_peer_base *base)
{
- struct inet_peer *u = rcu_dereference_bh(base->root);
+ struct inet_peer *u = rcu_dereference(base->root);
int count = 0;
while (u != peer_avl_empty) {
@@ -231,9 +231,9 @@ static struct inet_peer *lookup_rcu_bh(const struct inetpeer_addr *daddr,
return u;
}
if (cmp == -1)
- u = rcu_dereference_bh(u->avl_left);
+ u = rcu_dereference(u->avl_left);
else
- u = rcu_dereference_bh(u->avl_right);
+ u = rcu_dereference(u->avl_right);
if (unlikely(++count == PEER_MAXDEPTH))
break;
}
@@ -470,11 +470,11 @@ struct inet_peer *inet_getpeer(struct inetpeer_addr *daddr, int create)
/* Look up for the address quickly, lockless.
* Because of a concurrent writer, we might not find an existing entry.
*/
- rcu_read_lock_bh();
+ rcu_read_lock();
sequence = read_seqbegin(&base->lock);
- p = lookup_rcu_bh(daddr, base);
+ p = lookup_rcu(daddr, base);
invalidated = read_seqretry(&base->lock, sequence);
- rcu_read_unlock_bh();
+ rcu_read_unlock();
if (p) {
/* The existing node has been found.
--
1.7.4.1
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH] inetpeer: Don't disable BH for initial fast RCU lookup.
2011-03-08 22:59 [PATCH] inetpeer: Don't disable BH for initial fast RCU lookup David Miller
@ 2011-03-13 10:04 ` Eric Dumazet
2011-03-13 23:42 ` David Miller
0 siblings, 1 reply; 5+ messages in thread
From: Eric Dumazet @ 2011-03-13 10:04 UTC (permalink / raw)
To: David Miller; +Cc: netdev
Le mardi 08 mars 2011 à 14:59 -0800, David Miller a écrit :
> If modifications on other cpus are ok, then modifications to
> the tree during lookup done by the local cpu are ok too.
>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> ---
> net/ipv4/inetpeer.c | 18 +++++++++---------
> 1 files changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
> index f604ffd..6442c35 100644
> --- a/net/ipv4/inetpeer.c
> +++ b/net/ipv4/inetpeer.c
> @@ -206,16 +206,16 @@ static int addr_compare(const struct inetpeer_addr *a,
> })
>
> /*
> - * Called with rcu_read_lock_bh()
> + * Called with rcu_read_lock()
> * Because we hold no lock against a writer, its quite possible we fall
> * in an endless loop.
> * But every pointer we follow is guaranteed to be valid thanks to RCU.
> * We exit from this function if number of links exceeds PEER_MAXDEPTH
> */
> -static struct inet_peer *lookup_rcu_bh(const struct inetpeer_addr *daddr,
> - struct inet_peer_base *base)
> +static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr,
> + struct inet_peer_base *base)
> {
> - struct inet_peer *u = rcu_dereference_bh(base->root);
> + struct inet_peer *u = rcu_dereference(base->root);
> int count = 0;
>
> while (u != peer_avl_empty) {
> @@ -231,9 +231,9 @@ static struct inet_peer *lookup_rcu_bh(const struct inetpeer_addr *daddr,
> return u;
> }
> if (cmp == -1)
> - u = rcu_dereference_bh(u->avl_left);
> + u = rcu_dereference(u->avl_left);
> else
> - u = rcu_dereference_bh(u->avl_right);
> + u = rcu_dereference(u->avl_right);
> if (unlikely(++count == PEER_MAXDEPTH))
> break;
> }
> @@ -470,11 +470,11 @@ struct inet_peer *inet_getpeer(struct inetpeer_addr *daddr, int create)
> /* Look up for the address quickly, lockless.
> * Because of a concurrent writer, we might not find an existing entry.
> */
> - rcu_read_lock_bh();
> + rcu_read_lock();
> sequence = read_seqbegin(&base->lock);
> - p = lookup_rcu_bh(daddr, base);
> + p = lookup_rcu(daddr, base);
> invalidated = read_seqretry(&base->lock, sequence);
> - rcu_read_unlock_bh();
> + rcu_read_unlock();
>
> if (p) {
> /* The existing node has been found.
David, I am not sure this is safe, since we use call_rcu_bh() when
freeing one item. One cpu could decide to kfree() one item while another
cpu could still use it.
rcu_read_lock_bh() was signalling to others cpu we were in a softirq
section, so we were delaying a possible kfree().
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] inetpeer: Don't disable BH for initial fast RCU lookup.
2011-03-13 10:04 ` Eric Dumazet
@ 2011-03-13 23:42 ` David Miller
2011-03-14 4:15 ` [PATCH net-next-2.6] inetpeer: should use call_rcu() variant Eric Dumazet
0 siblings, 1 reply; 5+ messages in thread
From: David Miller @ 2011-03-13 23:42 UTC (permalink / raw)
To: eric.dumazet; +Cc: netdev
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Sun, 13 Mar 2011 11:04:09 +0100
> David, I am not sure this is safe, since we use call_rcu_bh() when
> freeing one item. One cpu could decide to kfree() one item while another
> cpu could still use it.
>
> rcu_read_lock_bh() was signalling to others cpu we were in a softirq
> section, so we were delaying a possible kfree().
Ok, could we use normal call_rcu() to solve this then?
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH net-next-2.6] inetpeer: should use call_rcu() variant
2011-03-13 23:42 ` David Miller
@ 2011-03-14 4:15 ` Eric Dumazet
2011-03-14 6:22 ` David Miller
0 siblings, 1 reply; 5+ messages in thread
From: Eric Dumazet @ 2011-03-14 4:15 UTC (permalink / raw)
To: David Miller; +Cc: netdev
Le dimanche 13 mars 2011 à 16:42 -0700, David Miller a écrit :
> From: Eric Dumazet <eric.dumazet@gmail.com>
> Date: Sun, 13 Mar 2011 11:04:09 +0100
>
> > David, I am not sure this is safe, since we use call_rcu_bh() when
> > freeing one item. One cpu could decide to kfree() one item while another
> > cpu could still use it.
> >
> > rcu_read_lock_bh() was signalling to others cpu we were in a softirq
> > section, so we were delaying a possible kfree().
>
> Ok, could we use normal call_rcu() to solve this then?
Yes, this should be good.
Thanks
[PATCH net-next-2.6] inetpeer: should use call_rcu() variant
After commit 7b46ac4e77f3224a (inetpeer: Don't disable BH for initial
fast RCU lookup.), we should use call_rcu() to wait proper RCU grace
period.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
net/ipv4/inetpeer.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index 86b1d08..dd1b20e 100644
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -399,7 +399,7 @@ static void unlink_from_pool(struct inet_peer *p, struct inet_peer_base *base)
write_sequnlock_bh(&base->lock);
if (do_free)
- call_rcu_bh(&p->rcu, inetpeer_free_rcu);
+ call_rcu(&p->rcu, inetpeer_free_rcu);
else
/* The node is used again. Decrease the reference counter
* back. The loop "cleanup -> unlink_from_unused
^ permalink raw reply related [flat|nested] 5+ messages in thread
end of thread, other threads:[~2011-03-14 6:22 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
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2011-03-08 22:59 [PATCH] inetpeer: Don't disable BH for initial fast RCU lookup David Miller
2011-03-13 10:04 ` Eric Dumazet
2011-03-13 23:42 ` David Miller
2011-03-14 4:15 ` [PATCH net-next-2.6] inetpeer: should use call_rcu() variant Eric Dumazet
2011-03-14 6:22 ` David Miller
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