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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.
This is the top level of the FreeBSD source directory. This file was last revised on: $FreeBSD$ For copyright information, please see the file COPYRIGHT in this directory (additional copyright information also exists for some sources in this tree - please see the specific source directories for more information). The Makefile in this directory supports a number of targets for building components (or all) of the FreeBSD source tree, the most commonly used one being ``world'', which rebuilds and installs everything in the FreeBSD system from the source tree except the kernel, the kernel-modules and the contents of /etc. The ``buildkernel'' and ``installkernel'' targets build and install the kernel and the modules (see below). Please see the top of the Makefile in this directory for more information on the standard build targets and compile-time flags. Building a kernel is a somewhat more involved process, documentation for which can be found at: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/kernelconfig.html And in the config(8) man page. Note: If you want to build and install the kernel with the ``buildkernel'' and ``installkernel'' targets, you might need to build world before. More information is available in the handbook. The sample kernel configuration files reside in the sys/<arch>/conf sub-directory (assuming that you've installed the kernel sources), the file named GENERIC being the one used to build your initial installation kernel. The file NOTES contains entries and documentation for all possible devices, not just those commonly used. It is the successor of the ancient LINT file, but in contrast to LINT, it is not buildable as a kernel but a pure reference and documentation file. Source Roadmap: --------------- bin System/user commands. contrib Packages contributed by 3rd parties. crypto Cryptography stuff (see crypto/README). etc Template files for /etc. games Amusements. gnu Various commands and libraries under the GNU Public License. Please see gnu/COPYING* for more information. include System include files. kerberos5 Kerberos5 (Heimdal) package. lib System libraries. libexec System daemons. release Release building Makefile & associated tools. sbin System commands. secure Cryptographic libraries and commands. share Shared resources. sys Kernel sources. tools Utilities for regression testing and miscellaneous tasks. usr.bin User commands. usr.sbin System administration commands. For information on synchronizing your source tree with one or more of the FreeBSD Project's development branches, please see: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/synching.html