[src/trunk]: src/sys/arch/m68k/include m68k: __cpu_simple_unlock audit.

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

details:   https://anonhg.NetBSD.org/src/rev/d92f37b4b30f
branches:  trunk
changeset: 361541:d92f37b4b30f
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Sun Feb 13 13:41:44 2022 +0000

description:
m68k: __cpu_simple_unlock audit.

- Use `cc' clobbers in asm volatile because they touch the condition
  codes.

- Use `memory' clobbers in asm volatile so the compiler doesn't move
  up loads and stores in the critical section at _other_ addresses
  than the lock so they happen before __cpu_simple_lock or
  __cpu_simple_lock_try.

- Not sure if we have any (or if there even are any?) multicore m68k
  systems out there, but __cpu_simple_unlock needs __insn_barrier
  either way so the compiler doesn't delay loads and stores prior to
  __cpu_simple_unlock so they happen after it.

diffstat:

 sys/arch/m68k/include/lock.h |  11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diffs (39 lines):

diff -r 2b7d5131b714 -r d92f37b4b30f sys/arch/m68k/include/lock.h
--- a/sys/arch/m68k/include/lock.h      Sun Feb 13 13:41:26 2022 +0000
+++ b/sys/arch/m68k/include/lock.h      Sun Feb 13 13:41:44 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: lock.h,v 1.16 2019/11/29 20:05:49 riastradh Exp $      */
+/*     $NetBSD: lock.h,v 1.17 2022/02/13 13:41:44 riastradh Exp $      */
 
 /*-
  * Copyright (c) 2000 The NetBSD Foundation, Inc.
@@ -75,7 +75,9 @@
        __asm volatile(
                "1:     tas     %0      \n"
                "       jne     1b      \n"
-               : "=m" (*alp));
+               : "=m" (*alp)
+               : /* no inputs */
+               : "cc", "memory");
 }
 
 static __inline int
@@ -89,7 +91,9 @@
                "       jeq     1f      \n"
                "       moveq   #0, %1  \n"
                "1:                     \n"
-               : "=m" (*alp), "=d" (__rv));
+               : "=m" (*alp), "=d" (__rv)
+               : /* no inputs */
+               : "cc", "memory");
 
        return (__rv);
 }
@@ -98,6 +102,7 @@
 __cpu_simple_unlock(__cpu_simple_lock_t *alp)
 {
 
+       __insn_barrier();
        *alp = __SIMPLELOCK_UNLOCKED;
 }