net/smc: no socket state changes in tasklet context

Several state changes occur during SMC socket closing. Currently
state changes triggered locally occur in process context with
lock_sock() taken while state changes triggered by peer occur in
tasklet context with bh_lock_sock() taken. bh_lock_sock() does not
wait till a lock_sock(() task in process context is finished. This
may lead to races in socket state transitions resulting in dangling
SMC-sockets, or it may lead to duplicate SMC socket freeing.
This patch introduces a closing worker to run all state changes under
lock_sock().

Signed-off-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
Reviewed-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
Reported-by: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/smc/smc_cdc.c b/net/smc/smc_cdc.c
index 4c9c2f6..a7294ed 100644
--- a/net/smc/smc_cdc.c
+++ b/net/smc/smc_cdc.c
@@ -217,8 +217,13 @@
 		smc->sk.sk_err = ECONNRESET;
 		conn->local_tx_ctrl.conn_state_flags.peer_conn_abort = 1;
 	}
-	if (smc_cdc_rxed_any_close_or_senddone(conn))
-		smc_close_passive_received(smc);
+	if (smc_cdc_rxed_any_close_or_senddone(conn)) {
+		smc->sk.sk_shutdown |= RCV_SHUTDOWN;
+		if (smc->clcsock && smc->clcsock->sk)
+			smc->clcsock->sk->sk_shutdown |= RCV_SHUTDOWN;
+		sock_set_flag(&smc->sk, SOCK_DONE);
+		schedule_work(&conn->close_work);
+	}
 
 	/* piggy backed tx info */
 	/* trigger sndbuf consumer: RDMA write into peer RMBE and CDC */