[src/trunk]: src/sys/arch/arm/include Fix the barrier confusion. From Riastr...

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

details:   https://anonhg.NetBSD.org/src/rev/3e4ea3175143
branches:  trunk
changeset: 962009:3e4ea3175143
user:      skrll <skrll%NetBSD.org@localhost>
date:      Tue Apr 27 06:03:09 2021 +0000

description:
Fix the barrier confusion.  From Riastradh - thanks!.

diffstat:

 sys/arch/arm/include/lock.h |  39 +++++++++++++++++++--------------------
 1 files changed, 19 insertions(+), 20 deletions(-)

diffs (97 lines):

diff -r d6867de10afa -r 3e4ea3175143 sys/arch/arm/include/lock.h
--- a/sys/arch/arm/include/lock.h       Tue Apr 27 05:40:29 2021 +0000
+++ b/sys/arch/arm/include/lock.h       Tue Apr 27 06:03:09 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: lock.h,v 1.37 2021/04/26 16:35:54 skrll Exp $  */
+/*     $NetBSD: lock.h,v 1.38 2021/04/27 06:03:09 skrll Exp $  */
 
 /*-
  * Copyright (c) 2000, 2001 The NetBSD Foundation, Inc.
@@ -131,32 +131,34 @@
 }
 #endif /* !_ARM_ARCH_6 */
 
+/* load/dmb implies load-acquire */
 static __inline void
-__arm_membar_producer(void)
+__arm_load_dmb(void)
 {
 #if defined(_ARM_ARCH_7)
-       __asm __volatile("dsb" ::: "memory");
-#elif defined(_ARM_ARCH_6)
-       __asm __volatile("mcr\tp15,0,%0,c7,c10,4" :: "r"(0) : "memory");
-#endif
-}
-
-static __inline void
-__arm_membar_consumer(void)
-{
-#if defined(_ARM_ARCH_7)
-       __asm __volatile("dmb" ::: "memory");
+       __asm __volatile("dmb ish" ::: "memory");
 #elif defined(_ARM_ARCH_6)
        __asm __volatile("mcr\tp15,0,%0,c7,c10,5" :: "r"(0) : "memory");
 #endif
 }
 
+/* dmb/store implies store-release */
+static __inline void
+__arm_dmb_store(void)
+{
+#if defined(_ARM_ARCH_7)
+       __asm __volatile("dmb ish" ::: "memory");
+#elif defined(_ARM_ARCH_6)
+       __asm __volatile("mcr\tp15,0,%0,c7,c10,5" :: "r"(0) : "memory");
+#endif
+}
+
+
 static __inline void __unused
 __cpu_simple_lock_init(__cpu_simple_lock_t *__alp)
 {
 
        *__alp = __SIMPLELOCK_UNLOCKED;
-       __arm_membar_producer();
 }
 
 #if !defined(__thumb__) || defined(_ARM_ARCH_T2)
@@ -164,12 +166,11 @@
 __cpu_simple_lock(__cpu_simple_lock_t *__alp)
 {
 #if defined(_ARM_ARCH_6)
-       __arm_membar_consumer();
        do {
                /* spin */
        } while (__arm_load_exclusive(__alp) != __SIMPLELOCK_UNLOCKED
                 || __arm_store_exclusive(__alp, __SIMPLELOCK_LOCKED));
-       __arm_membar_producer();
+       __arm_load_dmb();
 #else
        while (__swp(__SIMPLELOCK_LOCKED, __alp) != __SIMPLELOCK_UNLOCKED)
                continue;
@@ -184,13 +185,12 @@
 __cpu_simple_lock_try(__cpu_simple_lock_t *__alp)
 {
 #if defined(_ARM_ARCH_6)
-       __arm_membar_consumer();
        do {
                if (__arm_load_exclusive(__alp) != __SIMPLELOCK_UNLOCKED) {
                        return 0;
                }
        } while (__arm_store_exclusive(__alp, __SIMPLELOCK_LOCKED));
-       __arm_membar_producer();
+       __arm_load_dmb();
        return 1;
 #else
        return (__swp(__SIMPLELOCK_LOCKED, __alp) == __SIMPLELOCK_UNLOCKED);
@@ -213,9 +213,8 @@
                    :: "r"(__SIMPLELOCK_UNLOCKED), "r"(__alp) : "memory");
        }
 #else
-       __arm_membar_consumer();
+       __arm_dmb_store();
        *__alp = __SIMPLELOCK_UNLOCKED;
-       __arm_membar_producer();
 #endif
 }