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/*-
* Copyright (c) 2004 Robert N. M. Watson
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#include "opt_mp_watchdog.h"
#include "opt_sched.h"
#ifdef SCHED_ULE
#error MP_WATCHDOG cannot currently be used with SCHED_ULE
#endif
#include <sys/param.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/pcpu.h>
#include <sys/proc.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <machine/smp.h>
#include <machine/apicreg.h>
#include <machine/apicvar.h>
#include <machine/mp_watchdog.h>
/*
* mp_watchdog hijacks the idle thread on a specified CPU, prevents new work
* from being scheduled there, and uses it as a "watchdog" to detect kernel
* failure on other CPUs. This is made reasonable by inclusion of logical
* processors in Xeon hardware. The watchdog is configured by setting the
* debug.watchdog sysctl/tunable to the CPU of interest. A callout will then
* begin executing reseting a timer that is gradually lowered by the watching
* thread. If the timer reaches 0, the watchdog fires by ether dropping
* directly to the debugger, or by sending an NMI IPI to the boot processor.
* This is a somewhat less efficient substitute for dedicated watchdog
* hardware, but can be quite an effective tool for debugging hangs.
*
* XXXRW: This should really use the watchdog(9)/watchdog(4) framework, but
* doesn't yet.
*/
static int watchdog_cpu = -1;
static int watchdog_dontfire = 1;
static int watchdog_timer = -1;
static int watchdog_nmi = 1;
TUNABLE_INT("debug.watchdog", &watchdog_cpu);
SYSCTL_INT(_debug, OID_AUTO, watchdog_nmi, CTLFLAG_RW, &watchdog_nmi, 0,
"IPI the boot processor with an NMI to enter the debugger");
static struct callout watchdog_callout;
static void watchdog_change(int wdcpu);
/*
* Number of seconds before the watchdog will fire if the callout fails to
* reset the timer.
*/
#define WATCHDOG_THRESHOLD 10
static void
watchdog_init(void *arg)
{
callout_init(&watchdog_callout, CALLOUT_MPSAFE);
if (watchdog_cpu != -1)
watchdog_change(watchdog_cpu);
}
/*
* This callout resets a timer until the watchdog kicks in. It acquires some
* critical locks to make sure things haven't gotten wedged with hose locks
* held.
*/
static void
watchdog_function(void *arg)
{
/*
* Since the timer ran, we must not be wedged. Acquire some critical
* locks to make sure. Then reset the timer.
*/
mtx_lock(&Giant);
watchdog_timer = WATCHDOG_THRESHOLD;
mtx_unlock(&Giant);
callout_reset(&watchdog_callout, 1 * hz, watchdog_function, NULL);
}
SYSINIT(watchdog_init, SI_SUB_DRIVERS, SI_ORDER_ANY, watchdog_init, NULL);
static void
watchdog_change(int wdcpu)
{
if (wdcpu == -1 || wdcpu == 0xffffffff) {
/*
* Disable the watchdog.
*/
watchdog_cpu = -1;
watchdog_dontfire = 1;
callout_stop(&watchdog_callout);
printf("watchdog stopped\n");
} else {
watchdog_timer = WATCHDOG_THRESHOLD;
watchdog_dontfire = 0;
watchdog_cpu = wdcpu;
callout_reset(&watchdog_callout, 1 * hz, watchdog_function,
NULL);
}
}
/*
* This sysctl sets which CPU is the watchdog CPU. Set to -1 or 0xffffffff
* to disable the watchdog.
*/
static int
sysctl_watchdog(SYSCTL_HANDLER_ARGS)
{
int error, temp;
temp = watchdog_cpu;
error = sysctl_handle_int(oidp, &temp, 0, req);
if (error)
return (error);
if (req->newptr != NULL)
watchdog_change(temp);
return (0);
}
SYSCTL_PROC(_debug, OID_AUTO, watchdog, CTLTYPE_INT|CTLFLAG_RW, 0, 0,
sysctl_watchdog, "I", "");
/*
* Drop into the debugger by sending an IPI NMI to the boot processor.
*/
static void
watchdog_ipi_nmi(void)
{
/*
* Deliver NMI to the boot processor. Why not?
*/
lapic_ipi_raw(APIC_DEST_DESTFLD | APIC_TRIGMOD_EDGE |
APIC_LEVEL_ASSERT | APIC_DESTMODE_PHY | APIC_DELMODE_NMI,
boot_cpu_id);
lapic_ipi_wait(-1);
}
/*
* ap_watchdog() is called by the SMP idle loop code. It works on the same
* premise that the disabling of logical processors does: that if the cpu is
* idle, then it can ignore the world from then on, as nothing will be
* scheduled on it. Leaving aside multi-runqueue schedulers (SCHED_ULE) and
* explicit process migration (sched_bind()), this is not an unreasonable
* assumption.
*/
void
ap_watchdog(u_int cpuid)
{
char old_pcomm[MAXCOMLEN + 1];
struct proc *p;
if (watchdog_cpu != cpuid)
return;
printf("watchdog started on cpu %d\n", cpuid);
p = curproc;
bcopy(p->p_comm, old_pcomm, MAXCOMLEN + 1);
snprintf(p->p_comm, MAXCOMLEN + 1, "mp_watchdog cpu %d", cpuid);
while (1) {
DELAY(1000000); /* One second. */
if (watchdog_cpu != cpuid)
break;
atomic_subtract_int(&watchdog_timer, 1);
if (watchdog_timer < 4)
printf("Watchdog timer: %d\n", watchdog_timer);
if (watchdog_timer == 0 && watchdog_dontfire == 0) {
printf("Watchdog firing!\n");
watchdog_dontfire = 1;
if (watchdog_nmi)
watchdog_ipi_nmi();
else
kdb_enter(KDB_WHY_WATCHDOG, "mp_watchdog");
}
}
bcopy(old_pcomm, p->p_comm, MAXCOMLEN + 1);
printf("watchdog stopped on cpu %d\n", cpuid);
}
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