Module Name: src
Committed By: riastradh
Date: Sat Sep 2 17:43:38 UTC 2023
Modified Files:
src/sys/kern: kern_heartbeat.c
src/sys/sys: sched.h
Log Message:
heartbeat(9): New flag SPCF_HEARTBEATSUSPENDED.
This way we can suspend heartbeats on a single CPU while the console
is in polling mode, not just when the CPU is offlined. This should
be rare, so it's not _convenient_, but it should enable us to fix
polling-mode console input when the hardclock timer is still running
on other CPUs.
To generate a diff of this commit:
cvs rdiff -u -r1.5 -r1.6 src/sys/kern/kern_heartbeat.c
cvs rdiff -u -r1.92 -r1.93 src/sys/sys/sched.h
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/kern_heartbeat.c
diff -u src/sys/kern/kern_heartbeat.c:1.5 src/sys/kern/kern_heartbeat.c:1.6
--- src/sys/kern/kern_heartbeat.c:1.5 Sun Jul 16 10:18:19 2023
+++ src/sys/kern/kern_heartbeat.c Sat Sep 2 17:43:37 2023
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_heartbeat.c,v 1.5 2023/07/16 10:18:19 riastradh Exp $ */
+/* $NetBSD: kern_heartbeat.c,v 1.6 2023/09/02 17:43:37 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 1.5 2023/07/16 10:18:19 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_heartbeat.c,v 1.6 2023/09/02 17:43:37 riastradh Exp $");
#ifdef _KERNEL_OPT
#include "opt_ddb.h"
@@ -127,17 +127,22 @@ void *heartbeat_sih __read_mostly;
* Suspend heartbeat monitoring of the current CPU.
*
* Called after the current CPU has been marked offline but before
- * it has stopped running. Caller must have preemption disabled.
+ * it has stopped running, or after IPL has been raised for
+ * polling-mode console input. Caller must have preemption
+ * disabled. Non-nestable. Reversed by heartbeat_resume.
*/
void
heartbeat_suspend(void)
{
+ struct cpu_info *ci = curcpu();
+ int s;
KASSERT(curcpu_stable());
+ KASSERT((ci->ci_schedstate.spc_flags & SPCF_HEARTBEATSUSPENDED) == 0);
- /*
- * Nothing to do -- we just check the SPCF_OFFLINE flag.
- */
+ s = splsched();
+ ci->ci_schedstate.spc_flags |= SPCF_HEARTBEATSUSPENDED;
+ splx(s);
}
/*
@@ -148,6 +153,8 @@ heartbeat_suspend(void)
* 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.
+ *
+ * Must be run at splsched.
*/
static void
heartbeat_resume_cpu(struct cpu_info *ci)
@@ -155,6 +162,7 @@ heartbeat_resume_cpu(struct cpu_info *ci
KASSERT(__predict_false(cold) || curcpu_stable());
KASSERT(__predict_false(cold) || ci == curcpu());
+ /* XXX KASSERT IPL_SCHED */
ci->ci_heartbeat_count = 0;
ci->ci_heartbeat_uptime_cache = time_uptime;
@@ -167,9 +175,8 @@ heartbeat_resume_cpu(struct cpu_info *ci
* Resume heartbeat monitoring of the current CPU.
*
* Called after the current CPU has started running but before it
- * has been marked online. Also used internally when starting up
- * heartbeat monitoring at boot or when the maximum period is set
- * from zero to nonzero. Caller must have preemption disabled.
+ * has been marked online, or when ending polling-mode input
+ * before IPL is restored. Caller must have preemption disabled.
*/
void
heartbeat_resume(void)
@@ -178,6 +185,7 @@ heartbeat_resume(void)
int s;
KASSERT(curcpu_stable());
+ KASSERT(ci->ci_schedstate.spc_flags & SPCF_HEARTBEATSUSPENDED);
/*
* Block heartbeats while we reset the state so we don't
@@ -185,6 +193,7 @@ heartbeat_resume(void)
* resetting the count and the uptime stamp.
*/
s = splsched();
+ ci->ci_schedstate.spc_flags &= ~SPCF_HEARTBEATSUSPENDED;
heartbeat_resume_cpu(ci);
splx(s);
}
@@ -198,8 +207,11 @@ heartbeat_resume(void)
static void
heartbeat_reset_xc(void *a, void *b)
{
+ int s;
- heartbeat_resume();
+ s = splsched();
+ heartbeat_resume_cpu(curcpu());
+ splx(s);
}
/*
@@ -488,7 +500,7 @@ select_patient(void)
* in the iteration order.
*/
for (CPU_INFO_FOREACH(cii, ci)) {
- if (ci->ci_schedstate.spc_flags & SPCF_OFFLINE)
+ if (ci->ci_schedstate.spc_flags & SPCF_HEARTBEATSUSPENDED)
continue;
if (passedcur) {
/*
@@ -565,7 +577,8 @@ heartbeat(void)
period_secs = atomic_load_relaxed(&heartbeat_max_period_secs);
if (__predict_false(period_ticks == 0) ||
__predict_false(period_secs == 0) ||
- __predict_false(curcpu()->ci_schedstate.spc_flags & SPCF_OFFLINE))
+ __predict_false(curcpu()->ci_schedstate.spc_flags &
+ SPCF_HEARTBEATSUSPENDED))
return;
/*
@@ -637,8 +650,8 @@ heartbeat(void)
* Verify that time is advancing on the patient CPU. If the
* delta exceeds UINT_MAX/2, that means it is already ahead by
* a little on the other CPU, and the subtraction went
- * negative, which is OK. If the CPU has been
- * offlined since we selected it, no worries.
+ * negative, which is OK. If the CPU's heartbeats have been
+ * suspended since we selected it, no worries.
*
* This uses the current CPU to ensure the other CPU has made
* progress, even if the other CPU's hard timer interrupt
@@ -650,7 +663,8 @@ heartbeat(void)
d = uptime - atomic_load_relaxed(&patient->ci_heartbeat_uptime_cache);
if (__predict_false(d > period_secs) &&
__predict_false(d < UINT_MAX/2) &&
- ((patient->ci_schedstate.spc_flags & SPCF_OFFLINE) == 0))
+ ((patient->ci_schedstate.spc_flags & SPCF_HEARTBEATSUSPENDED)
+ == 0))
defibrillate(patient, d);
}
@@ -661,11 +675,21 @@ heartbeat(void)
*/
#ifdef DDB
static unsigned
-db_read_unsigned(const unsigned *p)
+db_read_unsigned(const volatile unsigned *p)
{
unsigned x;
- db_read_bytes((db_addr_t)p, sizeof(x), (char *)&x);
+ db_read_bytes((db_addr_t)(uintptr_t)p, sizeof(x), (char *)&x);
+
+ return x;
+}
+
+static int
+db_read_signed(const volatile int *p)
+{
+ int x;
+
+ db_read_bytes((db_addr_t)(uintptr_t)p, sizeof(x), (char *)&x);
return x;
}
@@ -677,11 +701,13 @@ heartbeat_dump(void)
db_printf("Heartbeats:\n");
for (ci = db_cpu_first(); ci != NULL; ci = db_cpu_next(ci)) {
- db_printf("cpu%u: count %u uptime %u stamp %u\n",
+ db_printf("cpu%u: count %u uptime %u stamp %u%s\n",
db_read_unsigned(&ci->ci_index),
db_read_unsigned(&ci->ci_heartbeat_count),
db_read_unsigned(&ci->ci_heartbeat_uptime_cache),
- db_read_unsigned(&ci->ci_heartbeat_uptime_stamp));
+ db_read_unsigned(&ci->ci_heartbeat_uptime_stamp),
+ (db_read_signed(&ci->ci_schedstate.spc_flags) &
+ SPCF_HEARTBEATSUSPENDED ? " (suspended)" : ""));
}
}
#endif
Index: src/sys/sys/sched.h
diff -u src/sys/sys/sched.h:1.92 src/sys/sys/sched.h:1.93
--- src/sys/sys/sched.h:1.92 Thu Jul 13 12:06:20 2023
+++ src/sys/sys/sched.h Sat Sep 2 17:43:37 2023
@@ -1,4 +1,4 @@
-/* $NetBSD: sched.h,v 1.92 2023/07/13 12:06:20 riastradh Exp $ */
+/* $NetBSD: sched.h,v 1.93 2023/09/02 17:43:37 riastradh Exp $ */
/*-
* Copyright (c) 1999, 2000, 2001, 2002, 2007, 2008, 2019, 2020
@@ -188,6 +188,7 @@ struct schedstate_percpu {
#define SPCF_1STCLASS 0x0040 /* first class scheduling entity */
#define SPCF_CORE1ST 0x0100 /* first CPU in core */
#define SPCF_PACKAGE1ST 0x0200 /* first CPU in package */
+#define SPCF_HEARTBEATSUSPENDED 0x0400 /* heartbeat (temporarily) suspended */
#define SPCF_SWITCHCLEAR (SPCF_SEENRR|SPCF_SHOULDYIELD)
