[TCP]: Document non-trivial locking path in tcp_v{4,6}_get_port().
This trips up a lot of folks reading this code.
Put an unlikely() around the port-exhaustion test
for good measure.
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 5d91213..67c6708 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -242,9 +242,14 @@
tcp_port_rover = rover;
spin_unlock(&tcp_portalloc_lock);
- /* Exhausted local port range during search? */
+ /* Exhausted local port range during search? It is not
+ * possible for us to be holding one of the bind hash
+ * locks if this test triggers, because if 'remaining'
+ * drops to zero, we broke out of the do/while loop at
+ * the top level, not from the 'break;' statement.
+ */
ret = 1;
- if (remaining <= 0)
+ if (unlikely(remaining <= 0))
goto fail;
/* OK, here is the one we will use. HEAD is