[src/sommerfeld_i386mp_1]: src/sys/arch/i386/include Recent versions of gcc m...

[sommerfeld <sommerfeld%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/ed884d8e4e22
branches:  sommerfeld_i386mp_1
changeset: 482466:ed884d8e4e22
user:      sommerfeld <sommerfeld%NetBSD.org@localhost>
date:      Tue Dec 18 02:49:12 2001 +0000

description:
Recent versions of gcc may reorder instructions around inline
functions, breaking the semantics of splraise() and spllower(); to
counteract this, insert a "barrier" (empty asm) as a sequence point.

Reportedly fixes a stability problems on AMD dual-processor systems.

the code-gen barrier primitive will likely move to <sys/cdefs.h> once
we figure out what to call it; in the mean time define it locally.

diffstat:

 sys/arch/i386/include/intr.h |  15 ++++++++++++++-
 1 files changed, 14 insertions(+), 1 deletions(-)

diffs (43 lines):

diff -r ed933889df52 -r ed884d8e4e22 sys/arch/i386/include/intr.h
--- a/sys/arch/i386/include/intr.h      Fri Dec 14 20:32:24 2001 +0000
+++ b/sys/arch/i386/include/intr.h      Tue Dec 18 02:49:12 2001 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: intr.h,v 1.12.10.16 2001/07/19 08:57:30 sommerfeld Exp $       */
+/*     $NetBSD: intr.h,v 1.12.10.17 2001/12/18 02:49:12 sommerfeld Exp $       */
 
 /*-
  * Copyright (c) 1998, 2001 The NetBSD Foundation, Inc.
@@ -101,6 +101,17 @@
 static __inline void softintr __P((int));
 
 /*
+ * compiler barrier: prevent reordering of instructions.
+ * XXX something similar will move to <sys/cdefs.h>
+ * or thereabouts.
+ * This prevents the compiler from reordering code around
+ * this "instruction", acting as a sequence point for code generation.
+ */
+
+#define __splbarrier() __asm __volatile("":::"memory")
+
+
+/*
  * Add a mask to cpl, and return the old value of cpl.
  */
 static __inline int
@@ -111,6 +122,7 @@
 
        if (ncpl > ocpl)
                lapic_tpr = ncpl;
+       __splbarrier();
        return (ocpl);
 }
 
@@ -124,6 +136,7 @@
 {
        register int cmask;
 
+       __splbarrier();
        lapic_tpr = ncpl;
        cmask = IUNMASK(ncpl);
        if (ipending & cmask)