[src/trunk]: src/sys/kern heartbeat(9): Avoid xcall(9) while cold.

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

details:   https://anonhg.NetBSD.org/src/rev/fea334b7efb1
branches:  trunk
changeset: 377536:fea334b7efb1
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Sun Jul 16 10:18:07 2023 +0000

description:
heartbeat(9): Avoid xcall(9) while cold.

diffstat:

 sys/kern/kern_heartbeat.c |  45 ++++++++++++++++++++++++++++++++++++++-------
 1 files changed, 38 insertions(+), 7 deletions(-)

diffs (87 lines):

diff -r 2808942b7031 -r fea334b7efb1 sys/kern/kern_heartbeat.c
--- a/sys/kern/kern_heartbeat.c Sun Jul 16 07:30:54 2023 +0000
+++ b/sys/kern/kern_heartbeat.c Sun Jul 16 10:18:07 2023 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_heartbeat.c,v 1.3 2023/07/08 13:59:05 riastradh Exp $     */
+/*     $NetBSD: kern_heartbeat.c,v 1.4 2023/07/16 10:18:07 riastradh Exp $     */
 
 /*-
  * Copyright (c) 2023 The NetBSD Foundation, Inc.
@@ -78,7 +78,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_heartbeat.c,v 1.3 2023/07/08 13:59:05 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_heartbeat.c,v 1.4 2023/07/16 10:18:07 riastradh Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_ddb.h"
@@ -95,6 +95,7 @@
 #include <sys/errno.h>
 #include <sys/heartbeat.h>
 #include <sys/ipi.h>
+#include <sys/kernel.h>
 #include <sys/mutex.h>
 #include <sys/sysctl.h>
 #include <sys/systm.h>
@@ -140,6 +141,27 @@ heartbeat_suspend(void)
 }
 
 /*
+ * heartbeat_resume_cpu(ci)
+ *
+ *     Resume heartbeat monitoring of ci.
+ *
+ *     Called at startup while cold, and whenever heartbeat monitoring
+ *     is re-enabled after being disabled or the period is changed.
+ *     When not cold, ci must be the current CPU.
+ */
+static void
+heartbeat_resume_cpu(struct cpu_info *ci)
+{
+
+       KASSERT(__predict_false(cold) || curcpu_stable());
+       KASSERT(__predict_false(cold) || ci == curcpu());
+
+       ci->ci_heartbeat_count = 0;
+       ci->ci_heartbeat_uptime_cache = atomic_load_relaxed(&time_uptime);
+       ci->ci_heartbeat_uptime_stamp = 0;
+}
+
+/*
  * heartbeat_resume()
  *
  *     Resume heartbeat monitoring of the current CPU.
@@ -163,9 +185,7 @@ heartbeat_resume(void)
         * resetting the count and the uptime stamp.
         */
        s = splsched();
-       ci->ci_heartbeat_count = 0;
-       ci->ci_heartbeat_uptime_cache = atomic_load_relaxed(&time_uptime);
-       ci->ci_heartbeat_uptime_stamp = 0;
+       heartbeat_resume_cpu(ci);
        splx(s);
 }
 
@@ -212,8 +232,19 @@ set_max_period(unsigned max_period)
         * reasonably up-to-date time_uptime cache on all CPUs so we
         * don't think we had an instant heart attack.
         */
-       if (heartbeat_max_period_secs == 0 && max_period != 0)
-               xc_wait(xc_broadcast(0, &heartbeat_reset_xc, NULL, NULL));
+       if (heartbeat_max_period_secs == 0 && max_period != 0) {
+               if (cold) {
+                       CPU_INFO_ITERATOR cii;
+                       struct cpu_info *ci;
+
+                       for (CPU_INFO_FOREACH(cii, ci))
+                               heartbeat_resume_cpu(ci);
+               } else {
+                       const uint64_t ticket =
+                           xc_broadcast(0, &heartbeat_reset_xc, NULL, NULL);
+                       xc_wait(ticket);
+               }
+       }
 
        /*
         * Once the heartbeat state has been updated on all (online)