We trigger a soft lockup as we grab nametbl_lock twice if the node
has a pending node up/down or link up/down event while:
- we process an incoming named message in tipc_named_rcv() and
perform an tipc_update_nametbl().
- we have pending backlog items in the name distributor queue
during a nametable update using tipc_nametbl_publish() or
tipc_nametbl_withdraw().
The following are the call chain associated:
tipc_named_rcv() Grabs nametbl_lock
tipc_update_nametbl() (publish/withdraw)
tipc_node_subscribe()/unsubscribe()
tipc_node_write_unlock()
<< lockup occurs if an outstanding node/link event
exits, as we grabs nametbl_lock again >>
tipc_nametbl_withdraw() Grab nametbl_lock
tipc_named_process_backlog()
tipc_update_nametbl()
<< rest as above >>
The function tipc_node_write_unlock(), in addition to releasing the
lock processes the outstanding node/link up/down events. To do this,
we need to grab the nametbl_lock again leading to the lockup.
In this commit we fix the soft lockup by introducing a fast variant of
node_unlock(), where we just release the lock. We adapt the
node_subscribe()/node_unsubscribe() to use the fast variants.
Acked-by: Ying Xue <ying....@windriver.com>
Signed-off-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvara...@ericsson.com>
---
net/tipc/node.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/net/tipc/node.c b/net/tipc/node.c
index 2883f6a0ed98..796dec65944a 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -263,6 +263,11 @@ static void tipc_node_write_lock(struct tipc_node *n)
write_lock_bh(&n->lock);
}
+static void tipc_node_write_unlock_fast(struct tipc_node *n)
+{
+ write_unlock_bh(&n->lock);
+}
+
static void tipc_node_write_unlock(struct tipc_node *n)
{
struct net *net = n->net;
@@ -417,7 +422,7 @@ void tipc_node_subscribe(struct net *net, struct list_head
*subscr, u32 addr)
}
tipc_node_write_lock(n);
list_add_tail(subscr, &n->publ_list);
- tipc_node_write_unlock(n);
+ tipc_node_write_unlock_fast(n);
tipc_node_put(n);
}
@@ -435,7 +440,7 @@ void tipc_node_unsubscribe(struct net *net, struct
list_head *subscr, u32 addr)
}
tipc_node_write_lock(n);
list_del_init(subscr);
- tipc_node_write_unlock(n);
+ tipc_node_write_unlock_fast(n);
tipc_node_put(n);
}
--
2.1.4
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