[src/trunk]: src/sys/kern avoid pserialize usage in early boot

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

details:   https://anonhg.NetBSD.org/src/rev/5fe3da6ead10
branches:  trunk
changeset: 373368:5fe3da6ead10
user:      mrg <mrg%NetBSD.org@localhost>
date:      Sun Feb 05 21:18:05 2023 +0000

description:
avoid pserialize usage in early boot

there are DEBUG-only aprint_normal() calls early in eg, ksyms
setup that may happen before eg curcpu() is setup.  this is the
case in sparc64, where it sets up ksyms as early as it can so
that DDB has symbols early, which is before the curcpu() setup
is created, and thus the calls to pserialize_read_enter() and
pserialize_read_exit() attempt to access unmapped cpu_info and
due to being so early, the system faults to the prom.

simply use "cold" to determine whether to skip these pserialize
calls or not.

ok riastradh

XXX: pullup-10

diffstat:

 sys/kern/subr_prf.c |  11 +++++++----
 1 files changed, 7 insertions(+), 4 deletions(-)

diffs (46 lines):

diff -r 70f7374914b2 -r 5fe3da6ead10 sys/kern/subr_prf.c
--- a/sys/kern/subr_prf.c       Sun Feb 05 17:23:01 2023 +0000
+++ b/sys/kern/subr_prf.c       Sun Feb 05 21:18:05 2023 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_prf.c,v 1.196 2022/10/31 09:14:18 simonb Exp $    */
+/*     $NetBSD: subr_prf.c,v 1.197 2023/02/05 21:18:05 mrg Exp $       */
 
 /*-
  * Copyright (c) 1986, 1988, 1991, 1993
@@ -37,7 +37,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_prf.c,v 1.196 2022/10/31 09:14:18 simonb Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_prf.c,v 1.197 2023/02/05 21:18:05 mrg Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_ddb.h"
@@ -401,6 +401,7 @@
 {
        struct tty *ctp;
        int s;
+       bool do_ps = cold;
 
        ctp = NULL;     /* XXX gcc i386 -Os */
 
@@ -408,7 +409,8 @@
         * Ensure whatever constty points to can't go away while we're
         * trying to use it.
         */
-       s = pserialize_read_enter();
+       if (__predict_true(do_ps))
+               s = pserialize_read_enter();
 
        if (panicstr)
                atomic_store_relaxed(&constty, NULL);
@@ -429,7 +431,8 @@
        if ((flags & TOCONS) && ctp == NULL && c != '\0')
                (*v_putc)(c);
 
-       pserialize_read_exit(s);
+       if (__predict_true(do_ps))
+               pserialize_read_exit(s);
 }
 
 static void