Module Name: src
Committed By: riastradh
Date: Sun Feb 13 19:21:21 UTC 2022
Modified Files:
src/sys/arch/x86/x86: idt.c
Log Message:
x86: Membar audit in idt.c.
- idt_vec_free/alloc are obviously supposed to synchronize with a
happens-before relation, so use release/acquire.
- There is no store-before-load ordering needed, so omit membar_sync.
To generate a diff of this commit:
cvs rdiff -u -r1.15 -r1.16 src/sys/arch/x86/x86/idt.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/x86/x86/idt.c
diff -u src/sys/arch/x86/x86/idt.c:1.15 src/sys/arch/x86/x86/idt.c:1.16
--- src/sys/arch/x86/x86/idt.c:1.15 Thu Dec 23 02:07:21 2021
+++ src/sys/arch/x86/x86/idt.c Sun Feb 13 19:21:21 2022
@@ -1,4 +1,4 @@
-/* $NetBSD: idt.c,v 1.15 2021/12/23 02:07:21 yamaguchi Exp $ */
+/* $NetBSD: idt.c,v 1.16 2022/02/13 19:21:21 riastradh Exp $ */
/*-
* Copyright (c) 1996, 1997, 1998, 2000, 2009 The NetBSD Foundation, Inc.
@@ -65,7 +65,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: idt.c,v 1.15 2021/12/23 02:07:21 yamaguchi Exp $");
+__KERNEL_RCSID(0, "$NetBSD: idt.c,v 1.16 2022/02/13 19:21:21 riastradh Exp $");
#include "opt_pcpu_idt.h"
@@ -174,10 +174,14 @@ idt_vec_alloc(struct idt_vec *iv, int lo
return -1;
for (vec = low; vec <= high; vec++) {
- if (idt_allocmap[vec] == 0) {
- /* idt_vec_free() can be unlocked, so membar. */
- membar_sync();
- idt_allocmap[vec] = 1;
+ /* pairs with atomic_store_release in idt_vec_free */
+ if (atomic_load_acquire(&idt_allocmap[vec]) == 0) {
+ /*
+ * No ordering needed here (`relaxed') because
+ * access to free entries is serialized by
+ * cpu_lock or single-threaded operation.
+ */
+ atomic_store_relaxed(&idt_allocmap[vec], 1);
return vec;
}
}
@@ -204,7 +208,7 @@ idt_vec_set(struct idt_vec *iv, int vec,
idt_descriptor_t *idt;
char *idt_allocmap __diagused = iv->iv_allocmap;
- KASSERT(idt_allocmap[vec] == 1);
+ KASSERT(atomic_load_relaxed(&idt_allocmap[vec]) == 1);
idt = iv->iv_idt;
set_idtgate(&idt[vec], function, 0, SDT_SYS386IGT, SEL_KPL,
@@ -220,11 +224,12 @@ idt_vec_free(struct idt_vec *iv, int vec
idt_descriptor_t *idt;
char *idt_allocmap = iv->iv_allocmap;
- KASSERT(idt_allocmap[vec] == 1);
+ KASSERT(atomic_load_relaxed(&idt_allocmap[vec]) == 1);
idt = iv->iv_idt;
unset_idtgate(&idt[vec]);
- idt_allocmap[vec] = 0;
+ /* pairs with atomic_load_acquire in idt_vec_alloc */
+ atomic_store_release(&idt_allocmap[vec], 0);
}
bool
