From: Wilson Kok <w...@cumulusnetworks.com>
br_fdb_update() can be called in process context in the following way:
br_fdb_add() -> __br_fdb_add() -> br_fdb_update() (if NTF_USE flag is set)
so we need to use spin_lock_bh because there are softirq users of the
hash_lock. One easy way to reproduce this is to modify the bridge utility
to set NTF_USE, enable stp and then set maxageing to a low value so
br_fdb_cleanup() is called frequently and then just add new entries in
a loop. This happens because br_fdb_cleanup() is called from timer/softirq
context. These locks were _bh before commit f8ae737deea1
("[BRIDGE]: forwarding remove unneeded preempt and bh diasables")
and at the time that commit was correct because br_fdb_update() couldn't be
called from process context, but that changed after commit:
292d1398983f ("bridge: add NTF_USE support")
Signed-off-by: Wilson Kok <w...@cumulusnetworks.com>
Signed-off-by: Nikolay Aleksandrov <niko...@cumulusnetworks.com>
Fixes: 292d1398983f ("bridge: add NTF_USE support")
---
Nik: Something that just occurred - we can disable softirqs around the call
to br_fdb_update() in br_fdb_add() so we can keep the optimization.
What do you think ?
net/bridge/br_fdb.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index 7896cf143045..523d329a5bd1 100644
--- a/net/bridge/br_fdb.c
+++ b/net/bridge/br_fdb.c
@@ -569,7 +569,7 @@ void br_fdb_update(struct net_bridge *br, struct
net_bridge_port *source,
fdb_notify(br, fdb, RTM_NEWNEIGH);
}
} else {
- spin_lock(&br->hash_lock);
+ spin_lock_bh(&br->hash_lock);
if (likely(!fdb_find(head, addr, vid))) {
fdb = fdb_create(head, source, addr, vid);
if (fdb) {
@@ -581,7 +581,7 @@ void br_fdb_update(struct net_bridge *br, struct
net_bridge_port *source,
/* else we lose race and someone else inserts
* it first, don't bother updating
*/
- spin_unlock(&br->hash_lock);
+ spin_unlock_bh(&br->hash_lock);
}
}
--
1.7.10.4
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