6817506 Lock contention in kernel severely degrades clock-profiling on T5440 in SIGPROF handling

1 files changed, 9 insertions, 9 deletions

diff --git a/usr/src/uts/common/syscall/sigprocmask.c b/usr/src/uts/common/syscall/sigprocmask.c
index 8f7cf6113d..51afc4e643 100644
--- a/usr/src/uts/common/syscall/sigprocmask.c
+++ b/usr/src/uts/common/syscall/sigprocmask.c
@@ -2,9 +2,8 @@
  * CDDL HEADER START
  *
  * The contents of this file are subject to the terms of the
- * Common Development and Distribution License, Version 1.0 only
- * (the "License").  You may not use this file except in compliance
- * with the License.
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
  *
  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  * or http://www.opensolaris.org/os/licensing.
@@ -19,15 +18,13 @@
  *
  * CDDL HEADER END
  */
-/*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
-
 
 /*
- * Copyright 1994-2003 Sun Microsystems, Inc.  All rights reserved.
+ * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
+/*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -47,7 +44,11 @@ lwp_sigmask(int how, uint_t bits0, uint_t bits1)
 	proc_t *p = ttoproc(t);
 	rval_t rv;
 
-	mutex_enter(&p->p_lock);
+	/*
+	 * We don't need to acquire p->p_lock here;
+	 * we are manipulating thread-private data.
+	 */
+
 	schedctl_finish_sigblock(t);
 
 	bits0 &= (FILLSET0 & ~CANTMASK0);
@@ -75,7 +76,6 @@ lwp_sigmask(int how, uint_t bits0, uint_t bits1)
 		break;
 	}
 
-	mutex_exit(&p->p_lock);
 	return (rv.r_vals);
 }