diff --git a/sys/arch/sh3/sh3/exception.c b/sys/arch/sh3/sh3/exception.c
index d1e757345f51..c52fe38ed38a 100644
--- a/sys/arch/sh3/sh3/exception.c
+++ b/sys/arch/sh3/sh3/exception.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: exception.c,v 1.40 2007/08/27 00:22:20 uwe Exp $	*/
+/*	$NetBSD: exception.c,v 1.41 2007/09/24 01:17:15 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 1.40 2007/08/27 00:22:20 uwe Exp $");
+__KERNEL_RCSID(0, "$NetBSD: exception.c,v 1.41 2007/09/24 01:17:15 uwe Exp $");
 
 #include "opt_ddb.h"
 #include "opt_kgdb.h"
@@ -432,12 +432,6 @@ ast(struct lwp *l, struct trapframe *tf)
 {
 
 	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;
 	}
 
diff --git a/sys/arch/sh3/sh3/exception_vector.S b/sys/arch/sh3/sh3/exception_vector.S
index 54a9eff51727..d10ef10199da 100644
--- a/sys/arch/sh3/sh3/exception_vector.S
+++ b/sys/arch/sh3/sh3/exception_vector.S
@@ -1,4 +1,4 @@
-/*	$NetBSD: exception_vector.S,v 1.30 2007/08/20 01:05:23 uwe Exp $	*/
+/*	$NetBSD: exception_vector.S,v 1.31 2007/09/24 01:17:15 uwe Exp $	*/
 
 /*-
  * Copyright (c) 2002 The NetBSD Foundation, Inc.
@@ -53,7 +53,7 @@
 #define _ALIGN_TEXT	.align 5
 #include <sh3/asm.h>
 
-__KERNEL_RCSID(0, "$NetBSD: exception_vector.S,v 1.30 2007/08/20 01:05:23 uwe Exp $")
+__KERNEL_RCSID(0, "$NetBSD: exception_vector.S,v 1.31 2007/09/24 01:17:15 uwe Exp $")
 
 
 /*
@@ -467,12 +467,34 @@ NENTRY(sh_vector_interrupt)
 	mov.l	.Li_intc_intr, r0
 	jsr	@r0		/* intc_intr(ssr, spc, ssp) */
 	 nop
+
+	mov.l	@(TF_SSR, r14), r2
+	mov.l	.Li_PSL_MD, r1
+	tst	r1, r2			! tf->tf_ssr & PSL_MD == 0 ?
+	bt	.Li_return_to_user
+
+	!! Check for interrupted kernel RAS when returning to kernel
+	mov.l	@(TF_SPC, r14), r2
+	mov.l	.Li_ras_start, r3
+	cmp/hi	r3, r2			! spc > _lock_cas_ras_start ?
+	bf	.Li_return_from_interrupt
+
+	mov.l	.Li_ras_end, r1
+	cmp/hs	r1, r2			! spc >= _lock_cas_ras_end ?
+	bt	.Li_return_from_interrupt
+
+	bra	.Li_return_from_interrupt
+	 mov.l	r3, @(TF_SPC, r14)	! spc = _lock_cas_ras_start
+
+.Li_return_to_user:
 	/* Check for ASTs on exit to user mode. */
 	mov.l	.Li_curlwp, r0
 	mov.l	@r0, r4		/* 1st arg */
 	mov.l	.Li_ast, r0
 	jsr	@r0
 	 mov	r14, r5		/* 2nd arg */
+
+.Li_return_from_interrupt:
 	__EXCEPTION_RETURN
 
 	.align	5
@@ -480,6 +502,10 @@ NENTRY(sh_vector_interrupt)
 .Li_intc_intr:		.long	_C_LABEL(intc_intr)
 .Li_ast:		.long	_C_LABEL(ast)
 .Li_uvmexp_intrs:	.long	_C_LABEL(uvmexp) + UVMEXP_INTRS
+.Li_PSL_MD:		.long	0x40000000 /* PSL_MD */
+.Li_ras_start:		.long	_C_LABEL(_lock_cas_ras_start)
+.Li_ras_end:		.long	_C_LABEL(_lock_cas_ras_end)
+
 
 /* LINTSTUB: Var: char sh_vector_interrupt_end[1]; */
 VECTOR_END_MARKER(sh_vector_interrupt_end)
diff --git a/sys/arch/sh3/sh3/lock_stubs.S b/sys/arch/sh3/sh3/lock_stubs.S
index b0c1ccf3c4d3..f532ddac5732 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 1.8 2007/03/14 06:42:46 uwe Exp $	*/
+/*	$NetBSD: lock_stubs.S,v 1.9 2007/09/24 01:17:15 uwe Exp $	*/
 
 /*
  * Copyright (c) 2007 Valeriy E. Ushakov
@@ -45,7 +45,7 @@
  *	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.
+ *	done on return from interrupt.
  *
  *	Mutex stubs below depend on this function:
  *	    r4 - preserved, passed along to mutex_vector_{enter,exit}