[src/trunk]: src/sys/arch __cpu_simple_lock(9): Omit needless barriers in init.

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

details:   https://anonhg.NetBSD.org/src/rev/f4635ad0202f
branches:  trunk
changeset: 361160:f4635ad0202f
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Sat Feb 12 17:17:53 2022 +0000

description:
__cpu_simple_lock(9): Omit needless barriers in init.

It is, and always has been, the caller's responsibility to ensure the
lock is initialized before it can be used -- otherwise the memory
could hold garbage; it is nonsensical to even attempt locking
operations on it before initialization.

So there's no need to issue explicit barriers here.  The barrier
seems to have been introduced in sys/arch/alpha/alpha/lock_machdep.c
rev. 1.1 (since moved to inline asm in alpha/include/lock.h) and then
copied & pasted into several other architectures.

diffstat:

 sys/arch/alpha/include/lock.h   |   9 ++-------
 sys/arch/hppa/include/lock.h    |   4 ++--
 sys/arch/ia64/include/lock.h    |   3 +--
 sys/arch/powerpc/include/lock.h |   3 +--
 sys/arch/vax/include/lock.h     |  14 ++------------
 sys/arch/x86/include/lock.h     |   3 +--
 6 files changed, 9 insertions(+), 27 deletions(-)

diffs (123 lines):

diff -r 40a3ad087c55 -r f4635ad0202f sys/arch/alpha/include/lock.h
--- a/sys/arch/alpha/include/lock.h     Sat Feb 12 17:10:20 2022 +0000
+++ b/sys/arch/alpha/include/lock.h     Sat Feb 12 17:17:53 2022 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: lock.h,v 1.31 2021/04/03 14:56:13 thorpej Exp $ */
+/* $NetBSD: lock.h,v 1.32 2022/02/12 17:17:53 riastradh Exp $ */
 
 /*-
  * Copyright (c) 1998, 1999, 2000 The NetBSD Foundation, Inc.
@@ -69,12 +69,7 @@
 __cpu_simple_lock_init(__cpu_simple_lock_t *alp)
 {
 
-       __asm volatile(
-               "# BEGIN __cpu_simple_lock_init\n"
-               "       stl     $31, %0         \n"
-               "       mb                      \n"
-               "       # END __cpu_simple_lock_init"
-               : "=m" (*alp));
+       *alp = __SIMPLELOCK_UNLOCKED;
 }
 
 static __inline void
diff -r 40a3ad087c55 -r f4635ad0202f sys/arch/hppa/include/lock.h
--- a/sys/arch/hppa/include/lock.h      Sat Feb 12 17:10:20 2022 +0000
+++ b/sys/arch/hppa/include/lock.h      Sat Feb 12 17:17:53 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: lock.h,v 1.22 2019/11/29 20:05:29 riastradh Exp $      */
+/*     $NetBSD: lock.h,v 1.23 2022/02/12 17:17:53 riastradh Exp $      */
 
 /*-
  * Copyright (c) 1998, 1999, 2000, 2001 The NetBSD Foundation, Inc.
@@ -85,10 +85,10 @@
 static __inline void
 __cpu_simple_lock_init(__cpu_simple_lock_t *alp)
 {
+
        alp->csl_lock[0] = alp->csl_lock[1] =
        alp->csl_lock[2] = alp->csl_lock[3] =
            __SIMPLELOCK_RAW_UNLOCKED;
-       __sync();
 }
 
 static __inline void
diff -r 40a3ad087c55 -r f4635ad0202f sys/arch/ia64/include/lock.h
--- a/sys/arch/ia64/include/lock.h      Sat Feb 12 17:10:20 2022 +0000
+++ b/sys/arch/ia64/include/lock.h      Sat Feb 12 17:17:53 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: lock.h,v 1.8 2019/11/29 20:05:38 riastradh Exp $       */
+/*     $NetBSD: lock.h,v 1.9 2022/02/12 17:17:53 riastradh Exp $       */
 
 /*-
  * Copyright (c) 2000 The NetBSD Foundation, Inc.
@@ -83,7 +83,6 @@
 {
 
        *lockp = __SIMPLELOCK_UNLOCKED;
-       __insn_barrier();
 }
 
 static __inline int
diff -r 40a3ad087c55 -r f4635ad0202f sys/arch/powerpc/include/lock.h
--- a/sys/arch/powerpc/include/lock.h   Sat Feb 12 17:10:20 2022 +0000
+++ b/sys/arch/powerpc/include/lock.h   Sat Feb 12 17:17:53 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: lock.h,v 1.16 2021/09/13 11:54:42 rin Exp $    */
+/*     $NetBSD: lock.h,v 1.17 2022/02/12 17:17:53 riastradh Exp $      */
 
 /*-
  * Copyright (c) 2000, 2007 The NetBSD Foundation, Inc.
@@ -64,7 +64,6 @@
 __cpu_simple_lock_init(__cpu_simple_lock_t *alp)
 {
        *alp = __SIMPLELOCK_UNLOCKED;
-       __asm volatile ("sync");
 }
 
 static __inline void
diff -r 40a3ad087c55 -r f4635ad0202f sys/arch/vax/include/lock.h
--- a/sys/arch/vax/include/lock.h       Sat Feb 12 17:10:20 2022 +0000
+++ b/sys/arch/vax/include/lock.h       Sat Feb 12 17:17:53 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: lock.h,v 1.32 2019/11/29 20:06:44 riastradh Exp $      */
+/*     $NetBSD: lock.h,v 1.33 2022/02/12 17:17:53 riastradh Exp $      */
 
 /*
  * Copyright (c) 2000 Ludd, University of Lule}, Sweden.
@@ -66,17 +66,7 @@
 static __inline void
 __cpu_simple_lock_init(__cpu_simple_lock_t *__alp)
 {
-#ifdef _HARDKERNEL
-       __asm __volatile ("movl %0,%%r1;jsb Sunlock"
-               : /* No output */
-               : "g"(__alp)
-               : "r1","cc","memory");
-#else
-       __asm __volatile ("bbcci $0,%0,1f;1:"
-               : /* No output */
-               : "m"(*__alp)
-               : "cc");
-#endif
+       *__alp = __SIMPLELOCK_UNLOCKED;
 }
 
 static __inline int __cpu_simple_lock_try(__cpu_simple_lock_t *);
diff -r 40a3ad087c55 -r f4635ad0202f sys/arch/x86/include/lock.h
--- a/sys/arch/x86/include/lock.h       Sat Feb 12 17:10:20 2022 +0000
+++ b/sys/arch/x86/include/lock.h       Sat Feb 12 17:17:53 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: lock.h,v 1.28 2017/09/16 23:55:45 christos Exp $       */
+/*     $NetBSD: lock.h,v 1.29 2022/02/12 17:17:54 riastradh Exp $      */
 
 /*-
  * Copyright (c) 2000, 2006 The NetBSD Foundation, Inc.
@@ -88,7 +88,6 @@
 {
 
        *lockp = __SIMPLELOCK_UNLOCKED;
-       __insn_barrier();
 }
 
 SPINLOCK_INLINE int