Cong Wang
2012-Jul-27 15:37 UTC
[Bridge] [PATCH 2/7] netpoll: make __netpoll_cleanup non-block
Like the previous patch, slave_disable_netpoll() and __netpoll_cleanup()
may be called with read_lock() held too, so we should make them
non-block, by moving the cleanup and kfree() to call_rcu_bh() callbacks.
Cc: "David S. Miller" <davem at davemloft.net>
Signed-off-by: Cong Wang <amwang at redhat.com>
---
drivers/net/bonding/bond_main.c | 4 +--
include/linux/netpoll.h | 3 ++
net/8021q/vlan_dev.c | 6 +----
net/bridge/br_device.c | 6 +----
net/core/netpoll.c | 42 +++++++++++++++++++++++++++++---------
5 files changed, 38 insertions(+), 23 deletions(-)
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index ab773d4..9907889 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1257,9 +1257,7 @@ static inline void slave_disable_netpoll(struct slave
*slave)
return;
slave->np = NULL;
- synchronize_rcu_bh();
- __netpoll_cleanup(np);
- kfree(np);
+ __netpoll_free_rcu(np);
}
static inline bool slave_dev_support_netpoll(struct net_device *slave_dev)
{
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index 28f5389..5011d74 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -23,6 +23,7 @@ struct netpoll {
u8 remote_mac[ETH_ALEN];
struct list_head rx; /* rx_np list element */
+ struct rcu_head rcu;
};
struct netpoll_info {
@@ -38,6 +39,7 @@ struct netpoll_info {
struct delayed_work tx_work;
struct netpoll *netpoll;
+ struct rcu_head rcu;
};
void netpoll_send_udp(struct netpoll *np, const char *msg, int len);
@@ -48,6 +50,7 @@ int netpoll_setup(struct netpoll *np);
int netpoll_trap(void);
void netpoll_set_trap(int trap);
void __netpoll_cleanup(struct netpoll *np);
+void __netpoll_free_rcu(struct netpoll *np);
void netpoll_cleanup(struct netpoll *np);
int __netpoll_rx(struct sk_buff *skb);
void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb,
diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index 73a2a83..43e14a2 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -703,11 +703,7 @@ static void vlan_dev_netpoll_cleanup(struct net_device
*dev)
info->netpoll = NULL;
- /* Wait for transmitting packets to finish before freeing. */
- synchronize_rcu_bh();
-
- __netpoll_cleanup(netpoll);
- kfree(netpoll);
+ __netpoll_free_rcu(netpoll);
}
#endif /* CONFIG_NET_POLL_CONTROLLER */
diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
index 3334845..bb6a5dd 100644
--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -267,11 +267,7 @@ void br_netpoll_disable(struct net_bridge_port *p)
p->np = NULL;
- /* Wait for transmitting packets to finish before freeing. */
- synchronize_rcu_bh();
-
- __netpoll_cleanup(np);
- kfree(np);
+ __netpoll_free_rcu(np);
}
#endif
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index c78a966..19dddef 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -878,6 +878,24 @@ static int __init netpoll_init(void)
}
core_initcall(netpoll_init);
+static void rcu_cleanup_netpoll_info(struct rcu_head *rcu_head)
+{
+ struct netpoll_info *npinfo + container_of(rcu_head, struct netpoll_info,
rcu);
+
+ skb_queue_purge(&npinfo->arp_tx);
+ skb_queue_purge(&npinfo->txq);
+
+ /* we can't call cancel_delayed_work_sync here, as we are in softirq*/
+ cancel_delayed_work(&npinfo->tx_work);
+
+ /* clean after last, unfinished work */
+ __skb_queue_purge(&npinfo->txq);
+ /* now cancel it again */
+ cancel_delayed_work(&npinfo->tx_work);
+ kfree(npinfo);
+}
+
void __netpoll_cleanup(struct netpoll *np)
{
struct netpoll_info *npinfo;
@@ -903,20 +921,24 @@ void __netpoll_cleanup(struct netpoll *np)
ops->ndo_netpoll_cleanup(np->dev);
RCU_INIT_POINTER(np->dev->npinfo, NULL);
+ call_rcu_bh(&npinfo->rcu, rcu_cleanup_netpoll_info);
+ }
+}
+EXPORT_SYMBOL_GPL(__netpoll_cleanup);
- /* avoid racing with NAPI reading npinfo */
- synchronize_rcu_bh();
+static void rcu_cleanup_netpoll(struct rcu_head *rcu_head)
+{
+ struct netpoll *np = container_of(rcu_head, struct netpoll, rcu);
- skb_queue_purge(&npinfo->arp_tx);
- skb_queue_purge(&npinfo->txq);
- cancel_delayed_work_sync(&npinfo->tx_work);
+ __netpoll_cleanup(np);
+ kfree(np);
+}
- /* clean after last, unfinished work */
- __skb_queue_purge(&npinfo->txq);
- kfree(npinfo);
- }
+void __netpoll_free_rcu(struct netpoll *np)
+{
+ call_rcu_bh(&np->rcu, rcu_cleanup_netpoll);
}
-EXPORT_SYMBOL_GPL(__netpoll_cleanup);
+EXPORT_SYMBOL_GPL(__netpoll_free_rcu);
void netpoll_cleanup(struct netpoll *np)
{
--
1.7.7.6
Neil Horman
2012-Jul-27 18:40 UTC
[Bridge] [PATCH 2/7] netpoll: make __netpoll_cleanup non-block
On Fri, Jul 27, 2012 at 11:37:59PM +0800, Cong Wang wrote:> Like the previous patch, slave_disable_netpoll() and __netpoll_cleanup() > may be called with read_lock() held too, so we should make them > non-block, by moving the cleanup and kfree() to call_rcu_bh() callbacks. > > Cc: "David S. Miller" <davem at davemloft.net> > Signed-off-by: Cong Wang <amwang at redhat.com> > --- > drivers/net/bonding/bond_main.c | 4 +-- > include/linux/netpoll.h | 3 ++ > net/8021q/vlan_dev.c | 6 +---- > net/bridge/br_device.c | 6 +---- > net/core/netpoll.c | 42 +++++++++++++++++++++++++++++--------- > 5 files changed, 38 insertions(+), 23 deletions(-) ><snip>> struct netpoll_info *npinfo; > @@ -903,20 +921,24 @@ void __netpoll_cleanup(struct netpoll *np) > ops->ndo_netpoll_cleanup(np->dev); > > RCU_INIT_POINTER(np->dev->npinfo, NULL); > + call_rcu_bh(&npinfo->rcu, rcu_cleanup_netpoll_info); > + } > +} > +EXPORT_SYMBOL_GPL(__netpoll_cleanup); > > - /* avoid racing with NAPI reading npinfo */ > - synchronize_rcu_bh(); > +static void rcu_cleanup_netpoll(struct rcu_head *rcu_head) > +{ > + struct netpoll *np = container_of(rcu_head, struct netpoll, rcu); > > - skb_queue_purge(&npinfo->arp_tx); > - skb_queue_purge(&npinfo->txq); > - cancel_delayed_work_sync(&npinfo->tx_work); > + __netpoll_cleanup(np); > + kfree(np); > +} > > - /* clean after last, unfinished work */ > - __skb_queue_purge(&npinfo->txq); > - kfree(npinfo); > - } > +void __netpoll_free_rcu(struct netpoll *np) > +{ > + call_rcu_bh(&np->rcu, rcu_cleanup_netpoll);Here, and above I see you using an rcu_head to defer cleanup, until after all pointer uses are dropped, but I don't see any modification of code points that dereference any struct netpoll pointers to include rcu_read_lock()/rcu_read_unlock(). Without those using rcu to defer cleanup is pointless, as the rcu code won't know when its safe to run. You're no better off that you would be just calling __netpoll_cleanup directly. Neil> } > -EXPORT_SYMBOL_GPL(__netpoll_cleanup); > +EXPORT_SYMBOL_GPL(__netpoll_free_rcu); > > void netpoll_cleanup(struct netpoll *np) > { > -- > 1.7.7.6 > >
Cong Wang
2012-Jul-30 01:42 UTC
[Bridge] [PATCH 2/7] netpoll: make __netpoll_cleanup non-block
On Fri, 2012-07-27 at 14:40 -0400, Neil Horman wrote:> Here, and above I see you using an rcu_head to defer cleanup, until after all > pointer uses are dropped, but I don't see any modification of code points that > dereference any struct netpoll pointers to include > rcu_read_lock()/rcu_read_unlock(). Without those using rcu to defer cleanup is > pointless, as the rcu code won't know when its safe to run. You're no better > off that you would be just calling __netpoll_cleanup directly.Hi, Neil, Actually they are protected by rcu_read_lock_bh() which is implied by local_irq_disable(), see: commit f0f9deae9e7c421fa0c1c627beb8e174325e1ba7 Author: Herbert Xu <herbert at gondor.apana.org.au> Date: Fri Sep 17 16:55:03 2010 -0700 netpoll: Disable IRQ around RCU dereference in netpoll_rx We cannot use rcu_dereference_bh safely in netpoll_rx as we may be called with IRQs disabled. We could however simply disable IRQs as that too causes BH to be disabled and is safe in either case. Thanks to John Linville for discovering this bug and providing a patch. Signed-off-by: Herbert Xu <herbert at gondor.apana.org.au> Signed-off-by: David S. Miller <davem at davemloft.net> Thanks.