docs: RCU: Convert torture.txt to ReST

- Add a SPDX header;
- Adjust document and section titles;
- Some whitespace fixes and new line breaks;
- Mark literal blocks as such;
- Add it to RCU/index.rst.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

1 files changed, 0 insertions, 282 deletions

diff --git a/Documentation/RCU/torture.txt b/Documentation/RCU/torture.txt
deleted file mode 100644
index af712a3c5b6a..000000000000
--- a/Documentation/RCU/torture.txt
+++ /dev/null
@@ -1,282 +0,0 @@
-RCU Torture Test Operation
-
-
-CONFIG_RCU_TORTURE_TEST
-
-The CONFIG_RCU_TORTURE_TEST config option is available for all RCU
-implementations.  It creates an rcutorture kernel module that can
-be loaded to run a torture test.  The test periodically outputs
-status messages via printk(), which can be examined via the dmesg
-command (perhaps grepping for "torture").  The test is started
-when the module is loaded, and stops when the module is unloaded.
-
-Module parameters are prefixed by "rcutorture." in
-Documentation/admin-guide/kernel-parameters.txt.
-
-OUTPUT
-
-The statistics output is as follows:
-
-	rcu-torture:--- Start of test: nreaders=16 nfakewriters=4 stat_interval=30 verbose=0 test_no_idle_hz=1 shuffle_interval=3 stutter=5 irqreader=1 fqs_duration=0 fqs_holdoff=0 fqs_stutter=3 test_boost=1/0 test_boost_interval=7 test_boost_duration=4
-	rcu-torture: rtc:           (null) ver: 155441 tfle: 0 rta: 155441 rtaf: 8884 rtf: 155440 rtmbe: 0 rtbe: 0 rtbke: 0 rtbre: 0 rtbf: 0 rtb: 0 nt: 3055767
-	rcu-torture: Reader Pipe:  727860534 34213 0 0 0 0 0 0 0 0 0
-	rcu-torture: Reader Batch:  727877838 17003 0 0 0 0 0 0 0 0 0
-	rcu-torture: Free-Block Circulation:  155440 155440 155440 155440 155440 155440 155440 155440 155440 155440 0
-	rcu-torture:--- End of test: SUCCESS: nreaders=16 nfakewriters=4 stat_interval=30 verbose=0 test_no_idle_hz=1 shuffle_interval=3 stutter=5 irqreader=1 fqs_duration=0 fqs_holdoff=0 fqs_stutter=3 test_boost=1/0 test_boost_interval=7 test_boost_duration=4
-
-The command "dmesg | grep torture:" will extract this information on
-most systems.  On more esoteric configurations, it may be necessary to
-use other commands to access the output of the printk()s used by
-the RCU torture test.  The printk()s use KERN_ALERT, so they should
-be evident.  ;-)
-
-The first and last lines show the rcutorture module parameters, and the
-last line shows either "SUCCESS" or "FAILURE", based on rcutorture's
-automatic determination as to whether RCU operated correctly.
-
-The entries are as follows:
-
-o	"rtc": The hexadecimal address of the structure currently visible
-	to readers.
-
-o	"ver": The number of times since boot that the RCU writer task
-	has changed the structure visible to readers.
-
-o	"tfle": If non-zero, indicates that the "torture freelist"
-	containing structures to be placed into the "rtc" area is empty.
-	This condition is important, since it can fool you into thinking
-	that RCU is working when it is not.  :-/
-
-o	"rta": Number of structures allocated from the torture freelist.
-
-o	"rtaf": Number of allocations from the torture freelist that have
-	failed due to the list being empty.  It is not unusual for this
-	to be non-zero, but it is bad for it to be a large fraction of
-	the value indicated by "rta".
-
-o	"rtf": Number of frees into the torture freelist.
-
-o	"rtmbe": A non-zero value indicates that rcutorture believes that
-	rcu_assign_pointer() and rcu_dereference() are not working
-	correctly.  This value should be zero.
-
-o	"rtbe": A non-zero value indicates that one of the rcu_barrier()
-	family of functions is not working correctly.
-
-o	"rtbke": rcutorture was unable to create the real-time kthreads
-	used to force RCU priority inversion.  This value should be zero.
-
-o	"rtbre": Although rcutorture successfully created the kthreads
-	used to force RCU priority inversion, it was unable to set them
-	to the real-time priority level of 1.  This value should be zero.
-
-o	"rtbf": The number of times that RCU priority boosting failed
-	to resolve RCU priority inversion.
-
-o	"rtb": The number of times that rcutorture attempted to force
-	an RCU priority inversion condition.  If you are testing RCU
-	priority boosting via the "test_boost" module parameter, this
-	value should be non-zero.
-
-o	"nt": The number of times rcutorture ran RCU read-side code from
-	within a timer handler.  This value should be non-zero only
-	if you specified the "irqreader" module parameter.
-
-o	"Reader Pipe": Histogram of "ages" of structures seen by readers.
-	If any entries past the first two are non-zero, RCU is broken.
-	And rcutorture prints the error flag string "!!!" to make sure
-	you notice.  The age of a newly allocated structure is zero,
-	it becomes one when removed from reader visibility, and is
-	incremented once per grace period subsequently -- and is freed
-	after passing through (RCU_TORTURE_PIPE_LEN-2) grace periods.
-
-	The output displayed above was taken from a correctly working
-	RCU.  If you want to see what it looks like when broken, break
-	it yourself.  ;-)
-
-o	"Reader Batch": Another histogram of "ages" of structures seen
-	by readers, but in terms of counter flips (or batches) rather
-	than in terms of grace periods.  The legal number of non-zero
-	entries is again two.  The reason for this separate view is that
-	it is sometimes easier to get the third entry to show up in the
-	"Reader Batch" list than in the "Reader Pipe" list.
-
-o	"Free-Block Circulation": Shows the number of torture structures
-	that have reached a given point in the pipeline.  The first element
-	should closely correspond to the number of structures allocated,
-	the second to the number that have been removed from reader view,
-	and all but the last remaining to the corresponding number of
-	passes through a grace period.  The last entry should be zero,
-	as it is only incremented if a torture structure's counter
-	somehow gets incremented farther than it should.
-
-Different implementations of RCU can provide implementation-specific
-additional information.  For example, Tree SRCU provides the following
-additional line:
-
-	srcud-torture: Tree SRCU per-CPU(idx=0): 0(35,-21) 1(-4,24) 2(1,1) 3(-26,20) 4(28,-47) 5(-9,4) 6(-10,14) 7(-14,11) T(1,6)
-
-This line shows the per-CPU counter state, in this case for Tree SRCU
-using a dynamically allocated srcu_struct (hence "srcud-" rather than
-"srcu-").  The numbers in parentheses are the values of the "old" and
-"current" counters for the corresponding CPU.  The "idx" value maps the
-"old" and "current" values to the underlying array, and is useful for
-debugging.  The final "T" entry contains the totals of the counters.
-
-
-USAGE ON SPECIFIC KERNEL BUILDS
-
-It is sometimes desirable to torture RCU on a specific kernel build,
-for example, when preparing to put that kernel build into production.
-In that case, the kernel should be built with CONFIG_RCU_TORTURE_TEST=m
-so that the test can be started using modprobe and terminated using rmmod.
-
-For example, the following script may be used to torture RCU:
-
-	#!/bin/sh
-
-	modprobe rcutorture
-	sleep 3600
-	rmmod rcutorture
-	dmesg | grep torture:
-
-The output can be manually inspected for the error flag of "!!!".
-One could of course create a more elaborate script that automatically
-checked for such errors.  The "rmmod" command forces a "SUCCESS",
-"FAILURE", or "RCU_HOTPLUG" indication to be printk()ed.  The first
-two are self-explanatory, while the last indicates that while there
-were no RCU failures, CPU-hotplug problems were detected.
-
-
-USAGE ON MAINLINE KERNELS
-
-When using rcutorture to test changes to RCU itself, it is often
-necessary to build a number of kernels in order to test that change
-across a broad range of combinations of the relevant Kconfig options
-and of the relevant kernel boot parameters.  In this situation, use
-of modprobe and rmmod can be quite time-consuming and error-prone.
-
-Therefore, the tools/testing/selftests/rcutorture/bin/kvm.sh
-script is available for mainline testing for x86, arm64, and
-powerpc.  By default, it will run the series of tests specified by
-tools/testing/selftests/rcutorture/configs/rcu/CFLIST, with each test
-running for 30 minutes within a guest OS using a minimal userspace
-supplied by an automatically generated initrd.  After the tests are
-complete, the resulting build products and console output are analyzed
-for errors and the results of the runs are summarized.
-
-On larger systems, rcutorture testing can be accelerated by passing the
---cpus argument to kvm.sh.  For example, on a 64-CPU system, "--cpus 43"
-would use up to 43 CPUs to run tests concurrently, which as of v5.4 would
-complete all the scenarios in two batches, reducing the time to complete
-from about eight hours to about one hour (not counting the time to build
-the sixteen kernels).  The "--dryrun sched" argument will not run tests,
-but rather tell you how the tests would be scheduled into batches.  This
-can be useful when working out how many CPUs to specify in the --cpus
-argument.
-
-Not all changes require that all scenarios be run.  For example, a change
-to Tree SRCU might run only the SRCU-N and SRCU-P scenarios using the
---configs argument to kvm.sh as follows:  "--configs 'SRCU-N SRCU-P'".
-Large systems can run multiple copies of of the full set of scenarios,
-for example, a system with 448 hardware threads can run five instances
-of the full set concurrently.  To make this happen:
-
-	kvm.sh --cpus 448 --configs '5*CFLIST'
-
-Alternatively, such a system can run 56 concurrent instances of a single
-eight-CPU scenario:
-
-	kvm.sh --cpus 448 --configs '56*TREE04'
-
-Or 28 concurrent instances of each of two eight-CPU scenarios:
-
-	kvm.sh --cpus 448 --configs '28*TREE03 28*TREE04'
-
-Of course, each concurrent instance will use memory, which can be
-limited using the --memory argument, which defaults to 512M.  Small
-values for memory may require disabling the callback-flooding tests
-using the --bootargs parameter discussed below.
-
-Sometimes additional debugging is useful, and in such cases the --kconfig
-parameter to kvm.sh may be used, for example, "--kconfig 'CONFIG_KASAN=y'".
-
-Kernel boot arguments can also be supplied, for example, to control
-rcutorture's module parameters.  For example, to test a change to RCU's
-CPU stall-warning code, use "--bootargs 'rcutorture.stall_cpu=30'".
-This will of course result in the scripting reporting a failure, namely
-the resuling RCU CPU stall warning.  As noted above, reducing memory may
-require disabling rcutorture's callback-flooding tests:
-
-	kvm.sh --cpus 448 --configs '56*TREE04' --memory 128M \
-		--bootargs 'rcutorture.fwd_progress=0'
-
-Sometimes all that is needed is a full set of kernel builds.  This is
-what the --buildonly argument does.
-
-Finally, the --trust-make argument allows each kernel build to reuse what
-it can from the previous kernel build.
-
-There are additional more arcane arguments that are documented in the
-source code of the kvm.sh script.
-
-If a run contains failures, the number of buildtime and runtime failures
-is listed at the end of the kvm.sh output, which you really should redirect
-to a file.  The build products and console output of each run is kept in
-tools/testing/selftests/rcutorture/res in timestamped directories.  A
-given directory can be supplied to kvm-find-errors.sh in order to have
-it cycle you through summaries of errors and full error logs.  For example:
-
-	tools/testing/selftests/rcutorture/bin/kvm-find-errors.sh \
-		tools/testing/selftests/rcutorture/res/2020.01.20-15.54.23
-
-However, it is often more convenient to access the files directly.
-Files pertaining to all scenarios in a run reside in the top-level
-directory (2020.01.20-15.54.23 in the example above), while per-scenario
-files reside in a subdirectory named after the scenario (for example,
-"TREE04").  If a given scenario ran more than once (as in "--configs
-'56*TREE04'" above), the directories corresponding to the second and
-subsequent runs of that scenario include a sequence number, for example,
-"TREE04.2", "TREE04.3", and so on.
-
-The most frequently used file in the top-level directory is testid.txt.
-If the test ran in a git repository, then this file contains the commit
-that was tested and any uncommitted changes in diff format.
-
-The most frequently used files in each per-scenario-run directory are:
-
-.config: This file contains the Kconfig options.
-
-Make.out: This contains build output for a specific scenario.
-
-console.log: This contains the console output for a specific scenario.
-	This file may be examined once the kernel has booted, but
-	it might not exist if the build failed.
-
-vmlinux: This contains the kernel, which can be useful with tools like
-	objdump and gdb.
-
-A number of additional files are available, but are less frequently used.
-Many are intended for debugging of rcutorture itself or of its scripting.
-
-As of v5.4, a successful run with the default set of scenarios produces
-the following summary at the end of the run on a 12-CPU system:
-
-SRCU-N ------- 804233 GPs (148.932/s) [srcu: g10008272 f0x0 ]
-SRCU-P ------- 202320 GPs (37.4667/s) [srcud: g1809476 f0x0 ]
-SRCU-t ------- 1122086 GPs (207.794/s) [srcu: g0 f0x0 ]
-SRCU-u ------- 1111285 GPs (205.794/s) [srcud: g1 f0x0 ]
-TASKS01 ------- 19666 GPs (3.64185/s) [tasks: g0 f0x0 ]
-TASKS02 ------- 20541 GPs (3.80389/s) [tasks: g0 f0x0 ]
-TASKS03 ------- 19416 GPs (3.59556/s) [tasks: g0 f0x0 ]
-TINY01 ------- 836134 GPs (154.84/s) [rcu: g0 f0x0 ] n_max_cbs: 34198
-TINY02 ------- 850371 GPs (157.476/s) [rcu: g0 f0x0 ] n_max_cbs: 2631
-TREE01 ------- 162625 GPs (30.1157/s) [rcu: g1124169 f0x0 ]
-TREE02 ------- 333003 GPs (61.6672/s) [rcu: g2647753 f0x0 ] n_max_cbs: 35844
-TREE03 ------- 306623 GPs (56.782/s) [rcu: g2975325 f0x0 ] n_max_cbs: 1496497
-CPU count limited from 16 to 12
-TREE04 ------- 246149 GPs (45.5831/s) [rcu: g1695737 f0x0 ] n_max_cbs: 434961
-TREE05 ------- 314603 GPs (58.2598/s) [rcu: g2257741 f0x2 ] n_max_cbs: 193997
-TREE07 ------- 167347 GPs (30.9902/s) [rcu: g1079021 f0x0 ] n_max_cbs: 478732
-CPU count limited from 16 to 12
-TREE09 ------- 752238 GPs (139.303/s) [rcu: g13075057 f0x0 ] n_max_cbs: 99011