docs: admin-guide: add a series of orphaned documents

There are lots of documents that belong to the admin-guide but
are on random places (most under Documentation root dir).

Move them to the admin guide.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

1 files changed, 0 insertions, 83 deletions

diff --git a/Documentation/lockup-watchdogs.txt b/Documentation/lockup-watchdogs.txt
deleted file mode 100644
index 290840c160af..000000000000
--- a/Documentation/lockup-watchdogs.txt
+++ /dev/null
@@ -1,83 +0,0 @@
-===============================================================
-Softlockup detector and hardlockup detector (aka nmi_watchdog)
-===============================================================
-
-The Linux kernel can act as a watchdog to detect both soft and hard
-lockups.
-
-A 'softlockup' is defined as a bug that causes the kernel to loop in
-kernel mode for more than 20 seconds (see "Implementation" below for
-details), without giving other tasks a chance to run. The current
-stack trace is displayed upon detection and, by default, the system
-will stay locked up. Alternatively, the kernel can be configured to
-panic; a sysctl, "kernel.softlockup_panic", a kernel parameter,
-"softlockup_panic" (see "Documentation/admin-guide/kernel-parameters.rst" for
-details), and a compile option, "BOOTPARAM_SOFTLOCKUP_PANIC", are
-provided for this.
-
-A 'hardlockup' is defined as a bug that causes the CPU to loop in
-kernel mode for more than 10 seconds (see "Implementation" below for
-details), without letting other interrupts have a chance to run.
-Similarly to the softlockup case, the current stack trace is displayed
-upon detection and the system will stay locked up unless the default
-behavior is changed, which can be done through a sysctl,
-'hardlockup_panic', a compile time knob, "BOOTPARAM_HARDLOCKUP_PANIC",
-and a kernel parameter, "nmi_watchdog"
-(see "Documentation/admin-guide/kernel-parameters.rst" for details).
-
-The panic option can be used in combination with panic_timeout (this
-timeout is set through the confusingly named "kernel.panic" sysctl),
-to cause the system to reboot automatically after a specified amount
-of time.
-
-Implementation
-==============
-
-The soft and hard lockup detectors are built on top of the hrtimer and
-perf subsystems, respectively. A direct consequence of this is that,
-in principle, they should work in any architecture where these
-subsystems are present.
-
-A periodic hrtimer runs to generate interrupts and kick the watchdog
-task. An NMI perf event is generated every "watchdog_thresh"
-(compile-time initialized to 10 and configurable through sysctl of the
-same name) seconds to check for hardlockups. If any CPU in the system
-does not receive any hrtimer interrupt during that time the
-'hardlockup detector' (the handler for the NMI perf event) will
-generate a kernel warning or call panic, depending on the
-configuration.
-
-The watchdog task is a high priority kernel thread that updates a
-timestamp every time it is scheduled. If that timestamp is not updated
-for 2*watchdog_thresh seconds (the softlockup threshold) the
-'softlockup detector' (coded inside the hrtimer callback function)
-will dump useful debug information to the system log, after which it
-will call panic if it was instructed to do so or resume execution of
-other kernel code.
-
-The period of the hrtimer is 2*watchdog_thresh/5, which means it has
-two or three chances to generate an interrupt before the hardlockup
-detector kicks in.
-
-As explained above, a kernel knob is provided that allows
-administrators to configure the period of the hrtimer and the perf
-event. The right value for a particular environment is a trade-off
-between fast response to lockups and detection overhead.
-
-By default, the watchdog runs on all online cores.  However, on a
-kernel configured with NO_HZ_FULL, by default the watchdog runs only
-on the housekeeping cores, not the cores specified in the "nohz_full"
-boot argument.  If we allowed the watchdog to run by default on
-the "nohz_full" cores, we would have to run timer ticks to activate
-the scheduler, which would prevent the "nohz_full" functionality
-from protecting the user code on those cores from the kernel.
-Of course, disabling it by default on the nohz_full cores means that
-when those cores do enter the kernel, by default we will not be
-able to detect if they lock up.  However, allowing the watchdog
-to continue to run on the housekeeping (non-tickless) cores means
-that we will continue to detect lockups properly on those cores.
-
-In either case, the set of cores excluded from running the watchdog
-may be adjusted via the kernel.watchdog_cpumask sysctl.  For
-nohz_full cores, this may be useful for debugging a case where the
-kernel seems to be hanging on the nohz_full cores.