Implement rw_cas for i386.

It uses a function pointer to choose between the 386 and 486 versions.
The 386 version is not MP safe, but we're not expecting MP support
for 386 cpus.

miod@ ok (and prodding)

2 files changed, 59 insertions, 2 deletions

diff --git a/sys/arch/i386/i386/lock_machdep.c b/sys/arch/i386/i386/lock_machdep.c
index 99e0bded4ac..3c00a13309e 100644
--- a/sys/arch/i386/i386/lock_machdep.c
+++ b/sys/arch/i386/i386/lock_machdep.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: lock_machdep.c,v 1.3 2006/09/19 11:06:33 jsg Exp $	*/
+/*	$OpenBSD: lock_machdep.c,v 1.4 2007/05/04 12:58:41 art Exp $	*/
 /* $NetBSD: lock_machdep.c,v 1.1.2.3 2000/05/03 14:40:30 sommerfeld Exp $ */
 
 /*-
@@ -50,6 +50,7 @@
 
 #include <machine/atomic.h>
 #include <machine/lock.h>
+#include <machine/cpufunc.h>
 
 #include <ddb/db_output.h>
 
@@ -106,3 +107,54 @@ __cpu_simple_unlock(__cpu_simple_lock_t *lockp)
 }
 
 #endif
+
+int rw_cas_386(volatile unsigned long *,  unsigned long, unsigned long);
+int rw_cas_486(volatile unsigned long *,  unsigned long, unsigned long);
+int rw_cas_choose(volatile unsigned long *,  unsigned long, unsigned long);
+
+int (*rw_cas_p)(volatile unsigned long *, unsigned long, unsigned long)
+    = rw_cas_choose;
+
+int
+rw_cas_choose(volatile unsigned long *p, unsigned long o, unsigned long n)
+{
+	if (cpu_class == CPUCLASS_386)
+		rw_cas_p = rw_cas_386;
+	else
+		rw_cas_p = rw_cas_486;
+
+	return (*rw_cas_p)(p, o, n);
+}
+
+int
+rw_cas_386(volatile unsigned long *p, unsigned long o, unsigned long n)
+{
+	u_int ef = read_eflags();
+
+	disable_intr();
+	if (*p != o) {
+		write_eflags(ef);
+		return (1);
+	}
+	*p = n;
+	write_eflags(ef);
+
+	return (0);
+}
+
+#ifdef MULTIPROCESSOR
+#define MPLOCK "lock "
+#else
+#define MPLOCK
+#endif
+
+int
+rw_cas_486(volatile unsigned long *p, unsigned long o, unsigned long n)
+{
+	int res;
+
+        __asm volatile(MPLOCK " cmpxchgl %2, %1" : "=a" (res), "=m" (*p)
+             : "r" (n), "a" (o), "m" (*p) : "memory");
+
+	return (res != o);
+}
diff --git a/sys/arch/i386/include/lock.h b/sys/arch/i386/include/lock.h
index fe0578a3139..172ed35fdf3 100644
--- a/sys/arch/i386/include/lock.h
+++ b/sys/arch/i386/include/lock.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: lock.h,v 1.3 2006/03/13 18:42:16 mickey Exp $	*/
+/*	$OpenBSD: lock.h,v 1.4 2007/05/04 12:58:41 art Exp $	*/
 /*	$NetBSD: lock.h,v 1.1.2.2 2000/05/03 14:40:55 sommerfeld Exp $	*/
 
 /*-
@@ -117,4 +117,9 @@ __cpu_simple_unlock(__cpu_simple_lock_t *lockp)
 
 #endif /* !LOCKDEBUG */
 
+#ifdef _KERNEL
+extern int (*rw_cas_p)(volatile unsigned long *, unsigned long, unsigned long);
+#define rw_cas (*rw_cas_p)
+#endif
+
 #endif /* _I386_LOCK_H_ */