Changed the implementation of the primitives to guarantee atomicity

with respect to interrupts on UP systems.  (The upgrade from gcc 2.7.x
to egcs 1.1.2 produced at least one non-atomic code sequence in
swap_pager_getpages.)

In addition, the primitives are now SMP-safe, but only on SMPs.  (For
portability between SMPs and UPs, modules are compiled with the SMP-safe
versions.)

Submitted by:	dillon and myself
Reviewed by:	bde

1 files changed, 42 insertions, 22 deletions

diff --git a/sys/i386/include/atomic.h b/sys/i386/include/atomic.h
index aae3484..7ebba20 100644
--- a/sys/i386/include/atomic.h
+++ b/sys/i386/include/atomic.h
@@ -23,36 +23,56 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id$
+ *	$Id: atomic.h,v 1.1 1998/08/24 08:39:36 dfr Exp $
  */
 #ifndef _MACHINE_ATOMIC_H_
 #define _MACHINE_ATOMIC_H_
 
 /*
  * Various simple arithmetic on memory which is atomic in the presence
- * of interrupts.
+ * of interrupts.  This code is now SMP safe as well.
  *
- * Note: these versions are not SMP safe.
+ * The assembly is volatilized to demark potential before-and-after side
+ * effects if an interrupt or SMP collision were to occurs.
  */
 
-#define atomic_set_char(P, V)		(*(u_char*)(P) |= (V))
-#define atomic_clear_char(P, V)		(*(u_char*)(P) &= ~(V))
-#define atomic_add_char(P, V)		(*(u_char*)(P) += (V))
-#define atomic_subtract_char(P, V)	(*(u_char*)(P) -= (V))
-
-#define atomic_set_short(P, V)		(*(u_short*)(P) |= (V))
-#define atomic_clear_short(P, V)	(*(u_short*)(P) &= ~(V))
-#define atomic_add_short(P, V)		(*(u_short*)(P) += (V))
-#define atomic_subtract_short(P, V)	(*(u_short*)(P) -= (V))
-
-#define atomic_set_int(P, V)		(*(u_int*)(P) |= (V))
-#define atomic_clear_int(P, V)		(*(u_int*)(P) &= ~(V))
-#define atomic_add_int(P, V)		(*(u_int*)(P) += (V))
-#define atomic_subtract_int(P, V)	(*(u_int*)(P) -= (V))
-
-#define atomic_set_long(P, V)		(*(u_long*)(P) |= (V))
-#define atomic_clear_long(P, V)		(*(u_long*)(P) &= ~(V))
-#define atomic_add_long(P, V)		(*(u_long*)(P) += (V))
-#define atomic_subtract_long(P, V)	(*(u_long*)(P) -= (V))
+#ifdef SMP
+#define ATOMIC_ASM(NAME, TYPE, OP, V)	\
+static __inline void			\
+NAME(void *p, TYPE v)			\
+{					\
+	__asm __volatile("lock; "	\
+			 OP : "=m" (*(TYPE *)p) : "ir" (V), "0" (*(TYPE *)p)); \
+}
+#else
+#define ATOMIC_ASM(NAME, TYPE, OP, V)	\
+static __inline void			\
+NAME(void *p, TYPE v)			\
+{					\
+	__asm __volatile(OP : "=m" (*(TYPE *)p) : "ir" (V), "0" (*(TYPE *)p)); \
+}
+#endif
+
+ATOMIC_ASM(atomic_set_char,	u_char, "orb %1,%0",   v)
+ATOMIC_ASM(atomic_clear_char,	u_char, "andb %1,%0", ~v)
+ATOMIC_ASM(atomic_add_char,	u_char, "addb %1,%0",  v)
+ATOMIC_ASM(atomic_subtract_char,u_char, "subb %1,%0",  v)
+
+ATOMIC_ASM(atomic_set_short,	u_short,"orw %1,%0",   v)
+ATOMIC_ASM(atomic_clear_short,	u_short,"andw %1,%0", ~v)
+ATOMIC_ASM(atomic_add_short,	u_short,"addw %1,%0",  v)
+ATOMIC_ASM(atomic_subtract_short,u_short,"subw %1,%0", v)
+
+ATOMIC_ASM(atomic_set_int,	u_int,	"orl %1,%0",   v)
+ATOMIC_ASM(atomic_clear_int,	u_int,	"andl %1,%0", ~v)
+ATOMIC_ASM(atomic_add_int,	u_int,	"addl %1,%0",  v)
+ATOMIC_ASM(atomic_subtract_int,	u_int,	"subl %1,%0",  v)
+
+ATOMIC_ASM(atomic_set_long,	u_long,	"orl %1,%0",   v)
+ATOMIC_ASM(atomic_clear_long,	u_long,	"andl %1,%0", ~v)
+ATOMIC_ASM(atomic_add_long,	u_long,	"addl %1,%0",  v)
+ATOMIC_ASM(atomic_subtract_long,u_long,	"subl %1,%0",  v)
+
+#undef ATOMIC_ASM
 
 #endif /* ! _MACHINE_ATOMIC_H_ */