[src/trunk]: src/sys/kern - If concurrent calls to kern_reboot(), only let th...

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

details:   https://anonhg.NetBSD.org/src/rev/d80624cd9c24
branches:  trunk
changeset: 745165:d80624cd9c24
user:      ad <ad%NetBSD.org@localhost>
date:      Sun Feb 23 20:06:30 2020 +0000

description:
- If concurrent calls to kern_reboot(), only let the first do the deed.
- Don't need kernel_lock for this (either OK, or suspendsched() called).

diffstat:

 sys/kern/kern_reboot.c |  17 +++++++++++++----
 1 files changed, 13 insertions(+), 4 deletions(-)

diffs (47 lines):

diff -r a9c9a80186f2 -r d80624cd9c24 sys/kern/kern_reboot.c
--- a/sys/kern/kern_reboot.c    Sun Feb 23 18:57:28 2020 +0000
+++ b/sys/kern/kern_reboot.c    Sun Feb 23 20:06:30 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_reboot.c,v 1.2 2020/01/01 22:57:17 thorpej Exp $  */
+/*     $NetBSD: kern_reboot.c,v 1.3 2020/02/23 20:06:30 ad Exp $       */
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1993
@@ -33,8 +33,9 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_reboot.c,v 1.2 2020/01/01 22:57:17 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_reboot.c,v 1.3 2020/02/23 20:06:30 ad Exp $");
 
+#include <sys/atomic.h>
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/proc.h>
@@ -50,7 +51,17 @@
 void
 kern_reboot(int howto, char *bootstr)
 {
+       static lwp_t *rebooter, *l;
 
+       /*
+        * If already rebooting then just hang out.  Allow reentry for the
+        * benfit of ddb, even if questionable.  It would be better to call
+        * exit1(), but this is called from all sorts of places.
+        */
+       l = atomic_cas_ptr(&rebooter, NULL, curlwp);
+       while (l != NULL && l != curlwp) {
+               (void)kpause("reboot", true, 0, NULL);
+       }
        shutting_down = 1;
 
        /*
@@ -87,8 +98,6 @@
        /*
         * Not all ports use the bootstr currently.
         */
-       KERNEL_LOCK(1, NULL);
        kern_reboot(SCARG(uap, opt), bootstr);
-       KERNEL_UNLOCK_ONE(NULL);
        return (0);
 }