When context switching, if the 'new' thread is the same as the 'old'

thread, then the save and restore of errno, FPU, and regs is unnecessary
and can be skipped.

"looks reasonable" marc@

1 files changed, 10 insertions, 1 deletions

diff --git a/lib/libpthread/uthread/uthread_kern.c b/lib/libpthread/uthread/uthread_kern.c
index fabb2088cd8..dab360b40fe 100644
--- a/lib/libpthread/uthread/uthread_kern.c
+++ b/lib/libpthread/uthread/uthread_kern.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_kern.c,v 1.37 2011/01/25 22:55:14 stsp Exp $	*/
+/*	$OpenBSD: uthread_kern.c,v 1.38 2011/07/07 09:25:16 guenther Exp $	*/
 /*
  * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
  * All rights reserved.
@@ -467,6 +467,13 @@ _thread_kern_sched(struct sigcontext * scp)
 				curthread->slice_usec = 0;
 			}
 
+			/*
+			 * If we're 'switching' to the current thread,
+			 * then don't bother with the save/restore
+			 */
+			if (curthread == old_thread_run)
+				goto after_switch;
+
 			/* Restore errno. */
 			errno = curthread->error;
 
@@ -487,6 +494,8 @@ _thread_kern_sched(struct sigcontext * scp)
 			 */
 			curthread = _get_curthread();
 
+		  after_switch:
+
 			/* Allow signals again. */
 			_queue_signals = 0;