[src/trunk]: src/sys/kern kern: Use atomic_store_release/atomic_load_consume ...

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

details:   https://anonhg.NetBSD.org/src/rev/0a193a545195
branches:  trunk
changeset: 363412:0a193a545195
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Thu Mar 10 12:21:35 2022 +0000

description:
kern: Use atomic_store_release/atomic_load_consume for pid_table.

This is read without the lock, so ordering is required.

diffstat:

 sys/kern/kern_proc.c |  10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)

diffs (45 lines):

diff -r 01f4f8da1ff9 -r 0a193a545195 sys/kern/kern_proc.c
--- a/sys/kern/kern_proc.c      Thu Mar 10 12:21:25 2022 +0000
+++ b/sys/kern/kern_proc.c      Thu Mar 10 12:21:35 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_proc.c,v 1.263 2022/02/12 15:51:29 thorpej Exp $  */
+/*     $NetBSD: kern_proc.c,v 1.264 2022/03/10 12:21:35 riastradh Exp $        */
 
 /*-
  * Copyright (c) 1999, 2006, 2007, 2008, 2020 The NetBSD Foundation, Inc.
@@ -62,7 +62,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_proc.c,v 1.263 2022/02/12 15:51:29 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_proc.c,v 1.264 2022/03/10 12:21:35 riastradh Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_kstack.h"
@@ -695,7 +695,7 @@
         * memory barrier for dependent loads on alpha.
         */
        s = pserialize_read_enter();
-       pt = &pid_table[pid & pid_tbl_mask];
+       pt = &atomic_load_consume(&pid_table)[pid & pid_tbl_mask];
        slot = atomic_load_consume(&pt->pt_slot);
        if (__predict_false(!PT_IS_LWP(slot))) {
                pserialize_read_exit(s);
@@ -753,7 +753,7 @@
         * care to read the slot atomically and only once.  This issues a
         * memory barrier for dependent loads on alpha.
         */
-       pt = &pid_table[pid & pid_tbl_mask];
+       pt = &atomic_load_consume(&pid_table)[pid & pid_tbl_mask];
        slot = atomic_load_consume(&pt->pt_slot);
        if (__predict_false(!PT_IS_LWP(slot))) {
                return NULL;
@@ -1003,7 +1003,7 @@
        /* Save old table size and switch tables */
        tsz = pt_size * sizeof(struct pid_table);
        n_pt = pid_table;
-       pid_table = new_pt;
+       atomic_store_release(&pid_table, new_pt);
        pid_tbl_mask = new_pt_mask;
 
        /*