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authorEric Dumazet <eric.dumazet@gmail.com>2010-09-13 12:24:54 +0000
committerDavid S. Miller <davem@davemloft.net>2010-09-14 14:27:29 -0700
commitef885afbf8a37689afc1d9d545e2f3e7a8276c17 (patch)
tree8defdc814be3668f906213b5f32729341eec2aa5
parentab12811c89e88f2e66746790b1fe4469ccb7bdd9 (diff)
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net: use rcu_barrier() in rollback_registered_many
netdev_wait_allrefs() waits that all references to a device vanishes. It currently uses a _very_ pessimistic 250 ms delay between each probe. Some users reported that no more than 4 devices can be dismantled per second, this is a pretty serious problem for some setups. Most of the time, a refcount is about to be released by an RCU callback, that is still in flight because rollback_registered_many() uses a synchronize_rcu() call instead of rcu_barrier(). Problem is visible if number of online cpus is one, because synchronize_rcu() is then a no op. time to remove 50 ipip tunnels on a UP machine : before patch : real 11.910s after patch : real 1.250s Reported-by: Nicolas Dichtel <nicolas.dichtel@6wind.com> Reported-by: Octavian Purdila <opurdila@ixiacom.com> Reported-by: Benjamin LaHaise <bcrl@kvack.org> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/core/dev.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/core/dev.c b/net/core/dev.c
index b9b22a3c4c8..660dd41aaaa 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4845,7 +4845,7 @@ static void rollback_registered_many(struct list_head *head)
dev = list_first_entry(head, struct net_device, unreg_list);
call_netdevice_notifiers(NETDEV_UNREGISTER_BATCH, dev);
- synchronize_net();
+ rcu_barrier();
list_for_each_entry(dev, head, unreg_list)
dev_put(dev);