Revert parts of tcp_input.c:1.255 associated with the header predicted

cases for tcp_input():

While it is true that the pcbinfo lock provides a pseudo-reference to
inpcbs, both the inpcb and pcbinfo locks are required to free an
un-referenced inpcb.  As such, we can release the pcbinfo lock as
long as the inpcb remains locked with the confidence that it will not
be garbage-collected.  This leads to a less conservative locking
strategy that should reduce contention on the TCP pcbinfo lock.

Discussed with: sam

1 files changed, 7 insertions, 2 deletions

diff --git a/sys/netinet/tcp_reass.c b/sys/netinet/tcp_reass.c
index 3eb7fc8..f3b158e 100644
--- a/sys/netinet/tcp_reass.c
+++ b/sys/netinet/tcp_reass.c
@@ -1153,6 +1153,8 @@ after_listen:
 			     ((tcp_do_newreno || tp->sack_enable) &&
 			      !IN_FASTRECOVERY(tp)))) {
 				KASSERT(headlocked, ("headlocked"));
+				INP_INFO_WUNLOCK(&tcbinfo);
+				headlocked = 0;
 				/*
 				 * this is a pure ack for outstanding data.
 				 */
@@ -1240,6 +1242,8 @@ after_listen:
 		    LIST_EMPTY(&tp->t_segq) &&
 		    tlen <= sbspace(&so->so_rcv)) {
 			KASSERT(headlocked, ("headlocked"));
+			INP_INFO_WUNLOCK(&tcbinfo);
+			headlocked = 0;
 			/*
 			 * this is a pure, in-sequence data packet
 			 * with nothing on the reassembly queue and
@@ -2373,6 +2377,8 @@ dodata:							/* XXX */
 			break;
 		}
 	}
+	INP_INFO_WUNLOCK(&tcbinfo);
+	headlocked = 0;
 #ifdef TCPDEBUG
 	if (so->so_options & SO_DEBUG)
 		tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
@@ -2386,7 +2392,7 @@ dodata:							/* XXX */
 		(void) tcp_output(tp);
 
 check_delack:
-	KASSERT(headlocked == 1, ("tcp_input: check_delack: head not locked"));
+	KASSERT(headlocked == 0, ("tcp_input: check_delack: head locked"));
 	INP_LOCK_ASSERT(inp);
 	if (tp->t_flags & TF_DELACK) {
 		tp->t_flags &= ~TF_DELACK;
@@ -2394,7 +2400,6 @@ check_delack:
 		    tcp_timer_delack, tp);
 	}
 	INP_UNLOCK(inp);
-	INP_INFO_WUNLOCK(&tcbinfo);
 	return;
 
 dropafterack: