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authorJon Paul Maloy <jon.maloy@ericsson.com>2016-06-17 06:35:57 -0400
committerDavid S. Miller <davem@davemloft.net>2016-06-17 21:38:10 -0700
commitf1d048f24e66ba85d3dabf3d076cefa5f2b546b0 (patch)
treec58a0cc946334eceba6c0dbafe95b5f30a9cd81f /lib/cpumask.c
parent695ef16cd0510f3bc963967fd73a360989fe4ebf (diff)
tipc: fix socket timer deadlock
We sometimes observe a 'deadly embrace' type deadlock occurring between mutually connected sockets on the same node. This happens when the one-hour peer supervision timers happen to expire simultaneously in both sockets. The scenario is as follows: CPU 1: CPU 2: -------- -------- tipc_sk_timeout(sk1) tipc_sk_timeout(sk2) lock(sk1.slock) lock(sk2.slock) msg_create(probe) msg_create(probe) unlock(sk1.slock) unlock(sk2.slock) tipc_node_xmit_skb() tipc_node_xmit_skb() tipc_node_xmit() tipc_node_xmit() tipc_sk_rcv(sk2) tipc_sk_rcv(sk1) lock(sk2.slock) lock((sk1.slock) filter_rcv() filter_rcv() tipc_sk_proto_rcv() tipc_sk_proto_rcv() msg_create(probe_rsp) msg_create(probe_rsp) tipc_sk_respond() tipc_sk_respond() tipc_node_xmit_skb() tipc_node_xmit_skb() tipc_node_xmit() tipc_node_xmit() tipc_sk_rcv(sk1) tipc_sk_rcv(sk2) lock((sk1.slock) lock((sk2.slock) ===> DEADLOCK ===> DEADLOCK Further analysis reveals that there are three different locations in the socket code where tipc_sk_respond() is called within the context of the socket lock, with ensuing risk of similar deadlocks. We now solve this by passing a buffer queue along with all upcalls where sk_lock.slock may potentially be held. Response or rejected message buffers are accumulated into this queue instead of being sent out directly, and only sent once we know we are safely outside the slock context. Reported-by: GUNA <gbalasun@gmail.com> Acked-by: Ying Xue <ying.xue@windriver.com> Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'lib/cpumask.c')
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