Add an "options MP_WATCHDOG" to i386. This option allows one of the

logical CPUs on a system to be used as a dedicated watchdog to cause a
drop to the debugger and/or generate an NMI to the boot processor if
the kernel ceases to respond.  A sysctl enables the watchdog running
out of the processor's idle thread; a callout is launched to reset a
timer in the watchdog.  If the callout fails to reset the timer for ten
seconds, the watchdog will fire.  The sysctl allows you to select which
CPU will run the watchdog.

A sample "debug.leak_schedlock" is included, which causes a sysctl to
spin holding sched_lock in order to trigger the watchdog.  On my Xeons,
the watchdog is able to detect this failure mode and break into the
debugger, which cannot otherwise be done without an NMI button.

This option does not currently work with sched_ule due to ule's push
notion of scheduling, similar to machdep.hlt_logical_cpus failing to
work with that scheduler.

On face value, this might seem somewhat inefficient, but there are a
lot of dual-processor Xeons with HTT around, so using one as a watchdog
for testing is not as inefficient as one might fear.

1 files changed, 34 insertions, 0 deletions

diff --git a/sys/amd64/include/mp_watchdog.h b/sys/amd64/include/mp_watchdog.h
new file mode 100644
index 0000000..bcec051
--- /dev/null
+++ b/sys/amd64/include/mp_watchdog.h
@@ -0,0 +1,34 @@
+/*-
+ * 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.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef	_MACHINE_MP_WATCHDOG_H_
+#define	_MACHINE_MP_WATCHDOG_H_
+
+void	ap_watchdog(u_int cpuid);
+
+#endif /* !_MACHINE_MP_WATCHDOG_H_ */