Fix PPC s_lock operations to work correctly on multi-CPU machines.

Need 'isync' during TAS and 'sync' during S_UNLOCK.

src/backend/storage/lmgr/s_lock.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/lmgr/s_lock.c,v 1.8 2002/06/20 20:29:35 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/lmgr/s_lock.c,v 1.9 2002/09/21 00:14:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -115,6 +115,9 @@ _success:						\n\
 /* used in darwin. */
 /* We key off __APPLE__ here because this function differs from
  * the LinuxPPC implementation only in compiler syntax.
+ *
+ * NOTE: per the Enhanced PowerPC Architecture manual, v1.0 dated 7-May-2002,
+ * an isync is a sufficient synchronization barrier after a lwarx/stwcx loop.
  */
 static void
 tas_dummy()
@@ -134,6 +137,7 @@ tas:							\n\
 fail:		li 		r3,1		\n\
 			blr 				\n\
 success:						\n\
+			isync				\n\
 			li 		r3,0		\n\
 			blr					\n\
 ");
@@ -158,6 +162,7 @@ tas:							\n\
 fail:		li		3,1 		\n\
 			blr 				\n\
 success:						\n\
+			isync				\n\
 			li 		3,0			\n\
 			blr					\n\
 ");

src/include/storage/s_lock.h

@@ -63,7 +63,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- *	  $Id: s_lock.h,v 1.100 2002/09/02 04:42:52 momjian Exp $
+ *	  $Id: s_lock.h,v 1.101 2002/09/21 00:14:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -217,6 +217,21 @@ tas(volatile slock_t *lock)
 #endif	 /* defined(__mc68000__) && defined(__linux__) */
 
 
+#if defined(__ppc__) || defined(__powerpc__)
+/*
+ * We currently use out-of-line assembler for TAS on PowerPC; see s_lock.c.
+ * S_UNLOCK is almost standard but requires a "sync" instruction.
+ */
+#define S_UNLOCK(lock)	\
+do \
+{\
+	__asm__ __volatile__ ("	sync \n"); \
+	*((volatile slock_t *) (lock)) = 0; \
+} while (0)
+
+#endif /* defined(__ppc__) || defined(__powerpc__) */
+
+
 #if defined(NEED_VAX_TAS_ASM)
 /*
  * VAXen -- even multiprocessor ones