net/smc: do not delete lgr from list twice

When 2 callers call smc_lgr_terminate() at the same time
for the same lgr, one gets the lgr_lock and deletes the lgr from the
list and releases the lock. Then the second caller gets the lock and
tries to delete it again.
In smc_lgr_terminate() add a check if the link group lgr is already
deleted from the link group list and prevent to try to delete it a
second time.
And add a check if the lgr is marked as freeing, which means that a
termination is already pending.

Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/smc/smc_core.c

@@ -629,7 +629,7 @@ void smc_lgr_terminate(struct smc_link_group *lgr, bool soft)
 
 	smc_lgr_list_head(lgr, &lgr_lock);
 	spin_lock_bh(lgr_lock);
-	if (lgr->terminating) {
+	if (list_empty(&lgr->list) || lgr->terminating || lgr->freeing) {
 		spin_unlock_bh(lgr_lock);
 		return;	/* lgr already terminating */
 	}