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authorLinus Torvalds <torvalds@linux-foundation.org>2024-11-20 09:16:45 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2024-11-20 09:16:45 -0800
commitc3cda60e83c803a3b3b832f371c776e57194b2f0 (patch)
tree2f5e1b95dfbae06cc447ef91f0b2066469c98313 /Documentation/admin-guide
parentbf9aa14fc523d2763fc9a10672a709224e8fcaf4 (diff)
parentc818d5c64c9a8cc14853d716bf7ce6674a6126d0 (diff)
Merge tag 'docs-6.13' of git://git.lwn.net/linux
Pull documentation updates from Jonathan Corbet: "Another moderately busy cycle in docsland: - Work on Chinese translations has picked up again. Happily, they are maintaining the existing translations and not just adding new ones. - Some maintenance of the Japanese and Italian translations as well. - The removal of the venerable "dontdiff" file. It has long outlived its usefulness and contained entries ("parse.*") that would actively mask actual source change. - The addition of enforcement information to the code-of-conduct documentation. Along with some build-system fixes and a lot of typo and language fixes" * tag 'docs-6.13' of git://git.lwn.net/linux: (52 commits) Documentation/CoC: spell out enforcement for unacceptable behaviors docs: fix typos and whitespace in Documentation/process/backporting.rst docs/zh_CN: fix one sentence in llvm.rst docs: bug-bisect: add a note about bisecting -next docs/zh_CN: add the translation of kbuild/llvm.rst Documentation: Fix incorrect paths/magic in magic numbers rst Documentation/maintainer-tip: Fix typos Documentation: Improve crash_kexec_post_notifiers description Docs/zh_CN: Translate physical_memory.rst to Simplified Chinese Documentation: admin: reorganize kernel-parameters intro docs/zh_CN: update the translation of process/programming-language.rst docs/zh_CN: update the translation of mm/page_owner.rst docs/zh_CN: update the translation of mm/page_table_check.rst docs/zh_CN: update the translation of mm/overcommit-accounting.rst docs/zh_CN: update the translation of mm/admon/faq.rst docs/zh_CN: update the translation of mm/active_mm.rst docs/zh_CN: update the translation of mm/hmm.rst docs: remove Documentation/dontdiff docs/zh_CN: Add a entry in Chinese glossary Docs/zh_CN: Fix the pfn calculation error in page_tables.rst ...
Diffstat (limited to 'Documentation/admin-guide')
-rw-r--r--Documentation/admin-guide/bug-bisect.rst21
-rw-r--r--Documentation/admin-guide/kernel-parameters.rst36
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt22
3 files changed, 60 insertions, 19 deletions
diff --git a/Documentation/admin-guide/bug-bisect.rst b/Documentation/admin-guide/bug-bisect.rst
index 585630d14581..f4f867cabb17 100644
--- a/Documentation/admin-guide/bug-bisect.rst
+++ b/Documentation/admin-guide/bug-bisect.rst
@@ -108,6 +108,27 @@ a fully reliable and straight-forward way to reproduce the regression, too.*
With that the process is complete. Now report the regression as described by
Documentation/admin-guide/reporting-issues.rst.
+Bisecting linux-next
+--------------------
+
+If you face a problem only happening in linux-next, bisect between the
+linux-next branches 'stable' and 'master'. The following commands will start
+the process for a linux-next tree you added as a remote called 'next'::
+
+ git bisect start
+ git bisect good next/stable
+ git bisect bad next/master
+
+The 'stable' branch refers to the state of linux-mainline that the current
+linux-next release (found in the 'master' branch) is based on -- the former
+thus should be free of any problems that show up in -next, but not in Linus'
+tree.
+
+This will bisect across a wide range of changes, some of which you might have
+used in earlier linux-next releases without problems. Sadly there is no simple
+way to avoid checking them: bisecting from one linux-next release to a later
+one (say between 'next-20241020' and 'next-20241021') is impossible, as they
+share no common history.
Additional reading material
---------------------------
diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst
index fdea7c26ef80..6247bbc9547c 100644
--- a/Documentation/admin-guide/kernel-parameters.rst
+++ b/Documentation/admin-guide/kernel-parameters.rst
@@ -27,6 +27,16 @@ kernel command line (/proc/cmdline) and collects module parameters
when it loads a module, so the kernel command line can be used for
loadable modules too.
+This document may not be entirely up to date and comprehensive. The command
+"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
+module. Loadable modules, after being loaded into the running kernel, also
+reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
+parameters may be changed at runtime by the command
+``echo -n ${value} > /sys/module/${modulename}/parameters/${parm}``.
+
+Special handling
+----------------
+
Hyphens (dashes) and underscores are equivalent in parameter names, so::
log_buf_len=1M print-fatal-signals=1
@@ -39,8 +49,8 @@ Double-quotes can be used to protect spaces in values, e.g.::
param="spaces in here"
-cpu lists:
-----------
+cpu lists
+~~~~~~~~~
Some kernel parameters take a list of CPUs as a value, e.g. isolcpus,
nohz_full, irqaffinity, rcu_nocbs. The format of this list is:
@@ -82,12 +92,17 @@ so that "nohz_full=all" is the equivalent of "nohz_full=0-N".
The semantics of "N" and "all" is supported on a level of bitmaps and holds for
all users of bitmap_parselist().
-This document may not be entirely up to date and comprehensive. The command
-"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
-module. Loadable modules, after being loaded into the running kernel, also
-reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
-parameters may be changed at runtime by the command
-``echo -n ${value} > /sys/module/${modulename}/parameters/${parm}``.
+Metric suffixes
+~~~~~~~~~~~~~~~
+
+The [KMG] suffix is commonly described after a number of kernel
+parameter values. 'K', 'M', 'G', 'T', 'P', and 'E' suffixes are allowed.
+These letters represent the _binary_ multipliers 'Kilo', 'Mega', 'Giga',
+'Tera', 'Peta', and 'Exa', equaling 2^10, 2^20, 2^30, 2^40, 2^50, and
+2^60 bytes respectively. Such letter suffixes can also be entirely omitted.
+
+Kernel Build Options
+--------------------
The parameters listed below are only valid if certain kernel build options
were enabled and if respective hardware is present. This list should be kept
@@ -211,10 +226,5 @@ a fixed number of characters. This limit depends on the architecture
and is between 256 and 4096 characters. It is defined in the file
./include/uapi/asm-generic/setup.h as COMMAND_LINE_SIZE.
-Finally, the [KMG] suffix is commonly described after a number of kernel
-parameter values. These 'K', 'M', and 'G' letters represent the _binary_
-multipliers 'Kilo', 'Mega', and 'Giga', equaling 2^10, 2^20, and 2^30
-bytes respectively. Such letter suffixes can also be entirely omitted:
-
.. include:: kernel-parameters.txt
:literal:
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 7e1315ee0507..2e66fef83468 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -921,12 +921,16 @@
the parameter has no effect.
crash_kexec_post_notifiers
- Run kdump after running panic-notifiers and dumping
- kmsg. This only for the users who doubt kdump always
- succeeds in any situation.
- Note that this also increases risks of kdump failure,
- because some panic notifiers can make the crashed
- kernel more unstable.
+ Only jump to kdump kernel after running the panic
+ notifiers and dumping kmsg. This option increases
+ the risks of a kdump failure, since some panic
+ notifiers can make the crashed kernel more unstable.
+ In configurations where kdump may not be reliable,
+ running the panic notifiers could allow collecting
+ more data on dmesg, like stack traces from other CPUS
+ or extra data dumped by panic_print. Note that some
+ configurations enable this option unconditionally,
+ like Hyper-V, PowerPC (fadump) and AMD SEV-SNP.
crashkernel=size[KMG][@offset[KMG]]
[KNL,EARLY] Using kexec, Linux can switch to a 'crash kernel'
@@ -6882,6 +6886,12 @@
reserve_mem=12M:4096:trace trace_instance=boot_map^traceoff^traceprintk@trace,sched,irq
+ Note, saving the trace buffer across reboots does require that the system
+ is set up to not wipe memory. For instance, CONFIG_RESET_ATTACK_MITIGATION
+ can force a memory reset on boot which will clear any trace that was stored.
+ This is just one of many ways that can clear memory. Make sure your system
+ keeps the content of memory across reboots before relying on this option.
+
See also Documentation/trace/debugging.rst