timeout_hardclock_update: enter timeout_mutex before reading uptime clock

We have no way of knowing how long we will spin before entering
timeout_mutex.  Enter timeout_mutex first, then wait until just before
we start dumping kclock buckets to read the uptime clock.

diff --git a/sys/kern/kern_timeout.c b/sys/kern/kern_timeout.c
index 9eccb02..b20616e 100644 (file)
--- a/sys/kern/kern_timeout.c
+++ b/sys/kern/kern_timeout.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: kern_timeout.c,v 1.92 2023/06/28 08:23:25 claudio Exp $       */
+/*     $OpenBSD: kern_timeout.c,v 1.93 2023/07/06 23:24:37 cheloha Exp $       */
 /*
  * Copyright (c) 2001 Thomas Nordin <nordin@openbsd.org>
  * Copyright (c) 2000-2001 Artur Grabowski <art@openbsd.org>
@@ -545,9 +545,6 @@ timeout_hardclock_update(void)
        struct timespec *lastscan = &timeout_kclock[KCLOCK_UPTIME].kc_lastscan;
        int b, done, first, i, last, level, need_softclock = 1, off;
 
-       nanouptime(&now);
-       timespecsub(&now, lastscan, &elapsed);
-
        mtx_enter(&timeout_mutex);
 
        MOVEBUCKET(0, ticks);
@@ -573,6 +570,8 @@ timeout_hardclock_update(void)
         * completed a lap of the level and need to process buckets in the
         * next level.
         */
+       nanouptime(&now);
+       timespecsub(&now, lastscan, &elapsed);
        for (level = 0; level < nitems(timeout_level_width); level++) {
                first = timeout_maskwheel(level, lastscan);
                if (elapsed.tv_sec >= timeout_level_width[level]) {