From 07a908343d2cd26ee5e6b35dd70116a2c1dc16ab Mon Sep 17 00:00:00 2001
From: uwe <uwe@NetBSD.org>
Date: Wed, 14 Mar 2007 05:03:52 +0000
Subject: [PATCH] Convert _lock_cas to RAS.  Check for restart in ast() on
 return from interrupt.

---
 sys/arch/sh3/sh3/exception.c  | 14 +++++++++++---
 sys/arch/sh3/sh3/lock_stubs.S | 22 ++++++++++------------
 2 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/sys/arch/sh3/sh3/exception.c b/sys/arch/sh3/sh3/exception.c
index cd8db0929188..fddb317bc83e 100644
--- a/sys/arch/sh3/sh3/exception.c
+++ b/sys/arch/sh3/sh3/exception.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: exception.c,v 1.35 2007/02/21 22:59:51 thorpej Exp $	*/
+/*	$NetBSD: exception.c,v 1.36 2007/03/14 05:03:52 uwe Exp $	*/
 
 /*-
  * Copyright (c) 2002 The NetBSD Foundation, Inc. All rights reserved.
@@ -79,7 +79,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: exception.c,v 1.35 2007/02/21 22:59:51 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: exception.c,v 1.36 2007/03/14 05:03:52 uwe Exp $");
 
 #include "opt_ddb.h"
 #include "opt_kgdb.h"
@@ -436,8 +436,16 @@ void
 ast(struct lwp *l, struct trapframe *tf)
 {
 
-	if (KERNELMODE(tf->tf_ssr))
+	if (KERNELMODE(tf->tf_ssr)) {
+		extern char _lock_cas_ras_start[];
+		extern char _lock_cas_ras_end[];
+
+		if ((uintptr_t)tf->tf_spc > (uintptr_t)_lock_cas_ras_start
+		    && (uintptr_t)tf->tf_spc < (uintptr_t)_lock_cas_ras_end)
+			tf->tf_spc = (uintptr_t)_lock_cas_ras_start;
 		return;
+	}
+
 	KDASSERT(l != NULL);
 	KDASSERT(l->l_md.md_regs == tf);
 
diff --git a/sys/arch/sh3/sh3/lock_stubs.S b/sys/arch/sh3/sh3/lock_stubs.S
index c796d1fb959f..7a15bcaa594d 100644
--- a/sys/arch/sh3/sh3/lock_stubs.S
+++ b/sys/arch/sh3/sh3/lock_stubs.S
@@ -1,4 +1,4 @@
-/*	$NetBSD: lock_stubs.S,v 1.5 2007/03/14 02:01:19 uwe Exp $	*/
+/*	$NetBSD: lock_stubs.S,v 1.6 2007/03/14 05:03:52 uwe Exp $	*/
 
 /*
  * Copyright (c) 2007 Valeriy E. Ushakov
@@ -42,25 +42,23 @@
 /*
  * LINTSTUB: Func: int _lock_cas(volatile uintptr_t *ptr, uintptr_t old, uintptr_t new);
  *
- *	Brute force with splhigh() for now.  Need to be redone as RAS.
+ *	Atomic compare-and-swap for kernel use.  SuperH machines are
+ *	uniprocessor, so we need to be atomic only w.r.t. interrupts.
+ *	Implement this as (the only in-kernel) RAS, with restart check
+ *	done in ast() on return from interrupt.
  */
 NENTRY(_lock_cas)
-	mov	#PSL_IMASK, r2	! 0xf0 - gets sign extended
-	stc	sr, r3
-	extu.b	r2, r2		! undo sign extention
-	mov	r3, r7		! preserve SR
-	or	r2, r3		! mask all interrupts
-	ldc	r3, sr
-
+ALTENTRY(_lock_cas_ras_start)
 	mov.l	@r4, r1
 	cmp/eq	r1, r5		! T = (*ptr == old)
 	bf.s	1f
 	 movt	r0		! retval = T
 	mov.l	r6, @r4		! *ptr = new
-1:
-	ldc	r7, sr		! restore SR (cannot be in delay slot)
-	rts
+ALTENTRY(_lock_cas_ras_end)
+1:	rts
 	 nop
+	SET_ENTRY_SIZE(_lock_cas)
+
 
 #if !defined(LOCKDEBUG)