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Andriy Gapon 353705930f panic: add a switch and infrastructure for stopping other CPUs in SMP case
Historical behavior of letting other CPUs merily go on is a default for
time being.  The new behavior can be switched on via
kern.stop_scheduler_on_panic tunable and sysctl.

Stopping of the CPUs has (at least) the following benefits:
- more of the system state at panic time is preserved intact
- threads and interrupts do not interfere with dumping of the system
  state

Only one thread runs uninterrupted after panic if stop_scheduler_on_panic
is set.  That thread might call code that is also used in normal context
and that code might use locks to prevent concurrent execution of certain
parts.  Those locks might be held by the stopped threads and would never
be released.  To work around this issue, it was decided that instead of
explicit checks for panic context, we would rather put those checks
inside the locking primitives.

This change has substantial portions written and re-written by attilio
and kib at various times.  Other changes are heavily based on the ideas
and patches submitted by jhb and mdf.  bde has provided many insights
into the details and history of the current code.

The new behavior may cause problems for systems that use a USB keyboard
for interfacing with system console.  This is because of some unusual
locking patterns in the ukbd code which have to be used because on one
hand ukbd is below syscons, but on the other hand it has to interface
with other usb code that uses regular mutexes/Giant for its concurrency
protection.  Dumping to USB-connected disks may also be affected.

PR:			amd64/139614 (at least)
In cooperation with:	attilio, jhb, kib, mdf
Discussed with:		arch@, bde
Tested by:		Eugene Grosbein <eugen@grosbein.net>,
			gnn,
			Steven Hartland <killing@multiplay.co.uk>,
			glebius,
			Andrew Boyer <aboyer@averesystems.com>
			(various versions of the patch)
MFC after:		3 months (or never)
2011-12-11 21:02:01 +00:00
bin Add static keywords to chio(1). 2011-12-11 20:53:12 +00:00
cddl Some mdoc(7) style and typo fixes to zfs(8). 2011-12-08 19:38:42 +00:00
contrib Include sys/queue.h: snmpmod.h uses TAILQ. 2011-12-11 17:10:33 +00:00
crypto Add a -x option that causes ssh-agent(1) to exit when all clients have 2011-10-07 13:10:16 +00:00
etc Fix style(9) issues from r228270. 2011-12-05 14:13:21 +00:00
games Add static keywords to variables and functions where possible in games/. 2011-11-05 07:18:53 +00:00
gnu Pull up vendor changes to mdoc(7). 2011-12-08 13:54:06 +00:00
include Vendor import of clang 3.0 final release: 2011-12-09 18:30:42 +00:00
kerberos5 Don't support OpenLDAP during lib32 build. 2011-12-06 12:03:01 +00:00
lib Use the correct upstream revision number for llvm/clang 3.0 release. 2011-12-10 01:01:44 +00:00
libexec Make comsat(8) approximately 15% smaller. 2011-12-10 18:35:26 +00:00
release - Based on a report on sparc64@ move V245 to the list of known working 2011-11-27 16:50:13 +00:00
rescue -lreadline is not required anymore. 2011-11-29 03:27:09 +00:00
sbin Add more static keywords to rcorder(8). 2011-12-11 20:48:40 +00:00
secure Force linker error when created shared library contains a relocation 2011-12-06 11:28:17 +00:00
share Minor whitespace cleanup to make.conf(5). 2011-12-11 20:01:37 +00:00
sys panic: add a switch and infrastructure for stopping other CPUs in SMP case 2011-12-11 21:02:01 +00:00
tools Add more files to cleanup with 'make delete-old' when WITHOUT_CLANG is 2011-12-11 14:01:11 +00:00
usr.bin Add more static keywords to truss(1) source code. 2011-12-10 18:27:55 +00:00
usr.sbin Add missing static keyword. 2011-12-11 19:22:42 +00:00
COPYRIGHT Happy New Year 2011. 2010-12-31 18:07:16 +00:00
LOCKS
MAINTAINERS Farewall, sysinstall! You served us well for many years, but 10.0 is one 2011-10-03 15:13:09 +00:00
Makefile Replace 'chflags' with 'file flags' in a comment, since 'chflags' 2011-11-20 20:05:47 +00:00
Makefile.inc1 - CTF knob is now implemented using common scheme: MK_CTF=yes/no is 2011-11-30 18:11:49 +00:00
Makefile.mips Retire TARGET_ABI. 2011-01-07 20:26:33 +00:00
ObsoleteFiles.inc Deorbit the broken amd(4) (see PR 124667), which was superseded by esp(4) 2011-11-25 19:29:21 +00:00
README
UPDATING Add an entry for r227823. 2011-11-30 20:08:30 +00:00

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 ``world''
target should only be used in cases where the source tree has not
changed from the currently running version.  See:
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/makeworld.html
for more information, including setting make(1) variables.

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.

cddl		Various commands and libraries under the Common Development
		and Distribution License.

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.

rescue		Build system for statically linked /rescue utilities.

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