svn commit: r272560 - head/sys/kern

[Mateusz Guzik]

Author: mjg
Date: Sun Oct  5 07:21:41 2014
New Revision: 272560
URL: https://svnweb.freebsd.org/changeset/base/272560

Log:
  Avoid unnecessary ppeers_lock acquisition in exit1.
  
  MFC after:	1 week

Modified:
  head/sys/kern/kern_exit.c

Modified: head/sys/kern/kern_exit.c
==============================================================================
--- head/sys/kern/kern_exit.c	Sun Oct  5 06:28:53 2014	(r272559)
+++ head/sys/kern/kern_exit.c	Sun Oct  5 07:21:41 2014	(r272560)
@@ -265,8 +265,8 @@ exit1(struct thread *td, int rv)
 	AUDIT_SYSCALL_EXIT(0, td);
 #endif
 
-	/* Are we a task leader? */
-	if (p == p->p_leader) {
+	/* Are we a task leader with peers? */
+	if (p->p_peers != NULL && p == p->p_leader) {
 		mtx_lock(&ppeers_lock);
 		q = p->p_peers;
 		while (q != NULL) {
@@ -337,15 +337,17 @@ exit1(struct thread *td, int rv)
 	/*
 	 * Remove ourself from our leader's peer list and wake our leader.
 	 */
-	mtx_lock(&ppeers_lock);
-	if (p->p_leader->p_peers) {
-		q = p->p_leader;
-		while (q->p_peers != p)
-			q = q->p_peers;
-		q->p_peers = p->p_peers;
-		wakeup(p->p_leader);
+	if (p->p_leader->p_peers != NULL) {
+		mtx_lock(&ppeers_lock);
+		if (p->p_leader->p_peers != NULL) {
+			q = p->p_leader;
+			while (q->p_peers != p)
+				q = q->p_peers;
+			q->p_peers = p->p_peers;
+			wakeup(p->p_leader);
+		}
+		mtx_unlock(&ppeers_lock);
 	}
-	mtx_unlock(&ppeers_lock);
 
 	vmspace_exit(td);