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.

this workaround uses the pre-existing "kprintf_inited" bool to
determine whether to skip these pserialize calls or not.


Index: kern/subr_prf.c
===================================================================
RCS file: /cvsroot/src/sys/kern/subr_prf.c,v
retrieving revision 1.196
diff -p -u -r1.196 subr_prf.c
--- kern/subr_prf.c	31 Oct 2022 09:14:18 -0000	1.196
+++ kern/subr_prf.c	4 Feb 2023 06:21:58 -0000
@@ -401,6 +401,7 @@ putone(int c, int flags, struct tty *tp)
 {
 	struct tty *ctp;
 	int s;
+	bool do_ps = kprintf_inited;
 
 	ctp = NULL;	/* XXX gcc i386 -Os */
 
@@ -408,7 +409,8 @@ putone(int c, int flags, struct tty *tp)
 	 * 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 @@ putone(int c, int flags, struct tty *tp)
 	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