| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.9 096/108] tipc: fix nametbl_lock soft lockup at node/link events | Date | Thu, 15 Jun 2017 19:53:42 +0200 |
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4.9-stable review patch. If anyone has any objections, please let me know.
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From: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
[ Upstream commit 93f955aad4bacee5acebad141d1a03cd51f27b4e ]
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.
Reported-and-Tested-by: John Thompson <thompa.atl@gmail.com> Acked-by: Ying Xue <ying.xue@windriver.com> Acked-by: Jon Maloy <jon.maloy@ericsson.com> Signed-off-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <alexander.levin@verizon.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- net/tipc/node.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
--- a/net/tipc/node.c +++ b/net/tipc/node.c @@ -263,6 +263,11 @@ static void tipc_node_write_lock(struct 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 } 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 *n } tipc_node_write_lock(n); list_del_init(subscr); - tipc_node_write_unlock(n); + tipc_node_write_unlock_fast(n); tipc_node_put(n); }
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