488 Commits
Author SHA1 Message Date
Paul E. McKenneyandJoel Fernandes ad6ef775cb rcu-tasks: Document that RCU Tasks Trace grace periods now imply RCU grace periods
Now that RCU Tasks Trace is implemented in terms of SRCU-fast, the fact
that each SRCU-fast grace period implies at least two RCU grace periods
in turn means that each RCU Tasks Trace grace period implies at least
two grace periods.  This commit therefore updates the documentation
accordingly.

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
2026-03-30 15:48:14 -04:00
Linus Torvalds 72c395024d Merge tag 'docs-7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/docs/linux
Pull documentation updates from Jonathan Corbet:
 "A slightly calmer cycle for docs this time around, though there is
  still a fair amount going on, including:

   - Some signs of life on the long-moribund Japanese translation

   - Documentation on policies around the use of generative tools for
     patch submissions, and a separate document intended for consumption
     by generative tools

   - The completion of the move of the documentation tools to
     tools/docs. For now we're leaving a /scripts/kernel-doc symlink
     behind to avoid breaking scripts

   - Ongoing build-system work includes the incorporation of
     documentation in Python code, better support for documenting
     variables, and lots of improvements and fixes

   - Automatic linking of man-page references -- cat(1), for example --
     to the online pages in the HTML build

  ...and the usual array of typo fixes and such"

* tag 'docs-7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/docs/linux: (107 commits)
  doc: development-process: add notice on testing
  tools: sphinx-build-wrapper: improve its help message
  docs: sphinx-build-wrapper: allow -v override -q
  docs: kdoc: Fix pdfdocs build for tools
  docs: ja_JP: process: translate 'Obtain a current source tree'
  docs: fix 're-use' -> 'reuse' in documentation
  docs: ioctl-number: fix a typo in ioctl-number.rst
  docs: filesystems: ensure proc pid substitutable is complete
  docs: automarkup.py: Skip common English words as C identifiers
  Documentation: use a source-read extension for the index link boilerplate
  docs: parse_features: make documentation more consistent
  docs: add parse_features module documentation
  docs: jobserver: do some documentation improvements
  docs: add jobserver module documentation
  docs: kabi: helpers: add documentation for each "enum" value
  docs: kabi: helpers: add helper for debug bits 7 and 8
  docs: kabi: system_symbols: end docstring phrases with a dot
  docs: python: abi_regex: do some improvements at documentation
  docs: python: abi_parser: do some improvements at documentation
  docs: add kabi modules documentation
  ...
2026-02-09 20:53:18 -08:00
Jani NikulaandJonathan Corbet a592a36e49 Documentation: use a source-read extension for the index link boilerplate
The root document usually has a special :ref:`genindex` link to the
generated index. This is also the case for Documentation/index.rst. The
other index.rst files deeper in the directory hierarchy usually don't.

For SPHINXDIRS builds, the root document isn't Documentation/index.rst,
but some other index.rst in the hierarchy. Currently they have a
".. only::" block to add the index link when doing SPHINXDIRS html
builds.

This is obviously very tedious and repetitive. The link is also added to
all index.rst files in the hierarchy for SPHINXDIRS builds, not just the
root document.

Put the boilerplate in a sphinx-includes/subproject-index.rst file, and
include it at the end of the root document for subproject builds in an
ad-hoc source-read extension defined in conf.py.

For now, keep having the boilerplate in translations, because this
approach currently doesn't cover translated index link headers.

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Tested-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
[jc: did s/doctree/kern_doc_dir/ ]
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20260123143149.2024303-1-jani.nikula@intel.com>
2026-01-23 11:59:34 -07:00
Paul E. McKenneyandBoqun Feng c0872be261 rcu: Update Requirements.rst for RCU Tasks Trace
This commit updates the documentation to declare that RCU Tasks Trace
is implemented as a thin wrapper around SRCU-fast.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: bpf@vger.kernel.org
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
2026-01-01 16:39:46 +08:00
Paul E. McKenneyandFrederic Weisbecker 8c8250ee3b doc: Update for SRCU-fast definitions and initialization
This commit documents the DEFINE_SRCU_FAST(), DEFINE_STATIC_SRCU_FAST(),
and init_srcu_struct_fast() API members.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: <bpf@vger.kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
2025-11-05 23:58:30 +01:00
Linus Torvalds 67da125e30 Merge tag 'rcu.2025.09.26a' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux
Pull RCU updates from Paul McKenney:
 "Documentation updates:

   - Update whatisRCU.rst and checklist.rst for recent RCU API additions

   - Fix RCU documentation formatting and typos

   - Replace dead Ottawa Linux Symposium links in RTFP.txt

  Miscellaneous RCU updates:

   - Document that rcu_barrier() hurries RCU_LAZY callbacks

   - Remove redundant interrupt disabling from
     rcu_preempt_deferred_qs_handler()

   - Move list_for_each_rcu from list.h to rculist.h, and adjust the
     include directive in kernel/cgroup/dmem.c accordingly

   - Make initial set of changes to accommodate upcoming
     system_percpu_wq changes

  SRCU updates:

   - Create an srcu_read_lock_fast_notrace() for eventual use in
     tracing, including adding guards

   - Document the reliance on per-CPU operations as implicit RCU readers
     in __srcu_read_{,un}lock_fast()

   - Document the srcu_flip() function's memory-barrier D's relationship
     to SRCU-fast readers

   - Remove a redundant preempt_disable() and preempt_enable() pair from
     srcu_gp_start_if_needed()

  Torture-test updates:

   - Fix jitter.sh spin time so that it actually varies as advertised.
     It is still quite coarse-grained, but at least it does now vary

   - Update torture.sh help text to include the not-so-new --do-normal
     parameter, which permits (for example) testing KCSAN kernels
     without doing non-debug kernels

   - Fix a number of false-positive diagnostics that were being
     triggered by rcutorture starting before boot completed. Running
     multiple near-CPU-bound rcutorture processes when there is only the
     boot CPU is after all a bit excessive

   - Substitute kcalloc() for kzalloc()

   - Remove a redundant kfree() and NULL out kfree()ed objects"

* tag 'rcu.2025.09.26a' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux: (31 commits)
  rcu: WQ_UNBOUND added to sync_wq workqueue
  rcu: WQ_PERCPU added to alloc_workqueue users
  rcu: replace use of system_wq with system_percpu_wq
  refperf: Set reader_tasks to NULL after kfree()
  refperf: Remove redundant kfree() after torture_stop_kthread()
  srcu/tiny: Remove preempt_disable/enable() in srcu_gp_start_if_needed()
  srcu: Document srcu_flip() memory-barrier D relation to SRCU-fast
  srcu: Document __srcu_read_{,un}lock_fast() implicit RCU readers
  rculist: move list_for_each_rcu() to where it belongs
  refscale: Use kcalloc() instead of kzalloc()
  rcutorture: Use kcalloc() instead of kzalloc()
  docs: rcu: Replace multiple dead OLS links in RTFP.txt
  doc: Fix typo in RCU's torture.rst documentation
  Documentation: RCU: Retitle toctree index
  Documentation: RCU: Reduce toctree depth
  Documentation: RCU: Wrap kvm-remote.sh rerun snippet in literal code block
  rcu: docs: Requirements.rst: Abide by conventions of kernel documentation
  doc: Add RCU guards to checklist.rst
  doc: Update whatisRCU.rst for recent RCU API additions
  rcutorture: Delay forward-progress testing until boot completes
  ...
2025-10-04 11:28:45 -07:00
Nikil Paul SandPaul E. McKenney de117fe3f5 docs: rcu: Replace multiple dead OLS links in RTFP.txt
This patch updates several dead OLS links in RTFP.txt, replacing them
with working copies hosted on kernel.org.

Originally posted as part of a 2-patch series, this is now being sent
as a standalone v4 patch to avoid confusion.

Signed-off-by: Nikil Paul S <snikilpaul@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2025-08-22 06:25:47 -07:00
Paul E. McKenney 14b0a12a70 doc: Fix typo in RCU's torture.rst documentation
s/you//

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2025-08-22 06:25:47 -07:00
Bagas SanjayaandPaul E. McKenney 9832258da7 Documentation: RCU: Retitle toctree index
toctree index title ("RCU concepts") is rather a misnomer: RCU concepts
is already described in rcu.rst, whereas the toctree suggests that
the docs themes about handbook on RCU subsystem instead.

Edit the title to reflect the fact.

Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2025-08-22 06:25:47 -07:00
Bagas SanjayaandPaul E. McKenney 326b16baed Documentation: RCU: Reduce toctree depth
toctree index for RCU currently has maximum depth of 3. Since no docs
currently use more than 3 section heading levels, this effectively spills
the entire docs hierarchy.

Tidy up by reducing toctree depth to 2 (only showing docs title and
second-level sections).

Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2025-08-22 06:25:47 -07:00
Bagas SanjayaandPaul E. McKenney 8495e00fe6 Documentation: RCU: Wrap kvm-remote.sh rerun snippet in literal code block
Unlike other kvm*.sh snippets in RCU torture test documentation,
kvm-remote.sh rerun snippet isn't formatted as literal code block,
causing it to be definition list instead in htmldocs output.

Wrap it like the rest.

Fixes: 0c208a7930 ("doc: Update torture.rst")
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
2025-08-22 06:25:47 -07:00
Akira YokosawaandPaul E. McKenney d33b01d793 rcu: docs: Requirements.rst: Abide by conventions of kernel documentation
Here is a list of conventions applied here:

- Don't mark up function names, to be taken care of by the automarkup
  extension.  Just say func().
- Instead of ".. code-block:: none", just say "::".
- Mark inline literals by a pair of ``xxxx``.  Don't use rust doc's
  dialect of `yyyy`.
- Instead of emphasizing headings by **strong emphasis**, use sub-level
  title adornments, in this case "^^^^^^^^^^" and make them proper
  sub-sections under "Hotplug CPU".

Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Cc: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2025-08-20 11:51:28 -07:00
Paul E. McKenney 820f8da73d doc: Add RCU guards to checklist.rst
Also note that RCU guards can be easier to use.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2025-08-20 11:51:28 -07:00
Paul E. McKenney 46e2c5d604 doc: Update whatisRCU.rst for recent RCU API additions
Bring this file kicking and screaming into the year 2025!

[ paulmck: Apply feedback from Bagas Sanjaya. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2025-08-20 11:51:02 -07:00
Bjorn HelgaasandJonathan Corbet aa7acf34c5 Documentation: Fix RCU typos
Fix typos.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20250813200526.290420-3-helgaas@kernel.org
2025-08-18 10:31:19 -06:00
Joel FernandesandNeeraj Upadhyay 5d71c2b53f rcu: Document concurrent quiescent state reporting for offline CPUs
The synchronization of CPU offlining with GP initialization is confusing
to put it mildly (rightfully so as the issue it deals with is complex).
Recent discussions brought up a question -- what prevents the
rcu_implicit_dyntick_qs() from warning about QS reports for offline
CPUs (missing QS reports for offline CPUs causing indefinite hangs).

QS reporting for now-offline CPUs should only happen from:
- gp_init()
- rcutree_cpu_report_dead()

Add some documentation on this and refer to it from comments in the code
explaining how QS reporting is not missed when these functions are
concurrently running.

I referred heavily to this post [1] about the need for the ofl_lock.
[1] https://lore.kernel.org/all/20180924164443.GF4222@linux.ibm.com/

[ Applied paulmck feedback on moving documentation to Requirements.rst ]

Link: https://lore.kernel.org/all/01b4d228-9416-43f8-a62e-124b92e8741a@paulmck-laptop/
Co-developed-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org>
2025-07-22 17:10:50 +05:30
Joel FernandesandNeeraj Upadhyay 186779c036 rcu: Document separation of rcu_state and rnp's gp_seq
The details of this are subtle and was discussed recently. Add a
quick-quiz about this and refer to it from the code, for more clarity.

Reviewed-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org>
2025-07-22 17:10:31 +05:30
Joel FernandesandNeeraj Upadhyay 30a7806ada rcu: Document GP init vs hotplug-scan ordering requirements
Add detailed comments explaining the critical ordering constraints
during RCU grace period initialization, based on discussions with
Frederic.

Reviewed-by: "Paul E. McKenney" <paulmck@kernel.org>
Co-developed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org>
2025-07-22 17:09:35 +05:30
Wei YangandJoel Fernandes 79ea7f43f8 doc/RCU/listRCU: refine example code for eliminating stale data
This patch adjust the example code with following two purpose:

  * reduce the confusion on not releasing e->lock
  * emphasize e is valid and not stale with e->lock held

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: Alan Huang <mmpgouride@gmail.com>
Reviewed-by: Alan Huang <mmpgouride@gmail.com>
Link: https://lore.kernel.org/r/20250218005047.27258-1-richard.weiyang@gmail.com
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
2025-05-16 09:00:54 -04:00
Paul E. McKenneyandJoel Fernandes 1708bf2cc4 doc: Update LWN RCU API links in whatisRCU.rst
This commit adds the 2024 LWN RCU API article set.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
2025-05-16 09:00:54 -04:00
Linus Torvalds eb0ece1602 Merge tag 'mm-stable-2025-03-30-16-52' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull MM updates from Andrew Morton:

 - The series "Enable strict percpu address space checks" from Uros
   Bizjak uses x86 named address space qualifiers to provide
   compile-time checking of percpu area accesses.

   This has caused a small amount of fallout - two or three issues were
   reported. In all cases the calling code was found to be incorrect.

 - The series "Some cleanup for memcg" from Chen Ridong implements some
   relatively monir cleanups for the memcontrol code.

 - The series "mm: fixes for device-exclusive entries (hmm)" from David
   Hildenbrand fixes a boatload of issues which David found then using
   device-exclusive PTE entries when THP is enabled. More work is
   needed, but this makes thins better - our own HMM selftests now
   succeed.

 - The series "mm: zswap: remove z3fold and zbud" from Yosry Ahmed
   remove the z3fold and zbud implementations. They have been deprecated
   for half a year and nobody has complained.

 - The series "mm: further simplify VMA merge operation" from Lorenzo
   Stoakes implements numerous simplifications in this area. No runtime
   effects are anticipated.

 - The series "mm/madvise: remove redundant mmap_lock operations from
   process_madvise()" from SeongJae Park rationalizes the locking in the
   madvise() implementation. Performance gains of 20-25% were observed
   in one MADV_DONTNEED microbenchmark.

 - The series "Tiny cleanup and improvements about SWAP code" from
   Baoquan He contains a number of touchups to issues which Baoquan
   noticed when working on the swap code.

 - The series "mm: kmemleak: Usability improvements" from Catalin
   Marinas implements a couple of improvements to the kmemleak
   user-visible output.

 - The series "mm/damon/paddr: fix large folios access and schemes
   handling" from Usama Arif provides a couple of fixes for DAMON's
   handling of large folios.

 - The series "mm/damon/core: fix wrong and/or useless damos_walk()
   behaviors" from SeongJae Park fixes a few issues with the accuracy of
   kdamond's walking of DAMON regions.

 - The series "expose mapping wrprotect, fix fb_defio use" from Lorenzo
   Stoakes changes the interaction between framebuffer deferred-io and
   core MM. No functional changes are anticipated - this is preparatory
   work for the future removal of page structure fields.

 - The series "mm/damon: add support for hugepage_size DAMOS filter"
   from Usama Arif adds a DAMOS filter which permits the filtering by
   huge page sizes.

 - The series "mm: permit guard regions for file-backed/shmem mappings"
   from Lorenzo Stoakes extends the guard region feature from its
   present "anon mappings only" state. The feature now covers shmem and
   file-backed mappings.

 - The series "mm: batched unmap lazyfree large folios during
   reclamation" from Barry Song cleans up and speeds up the unmapping
   for pte-mapped large folios.

 - The series "reimplement per-vma lock as a refcount" from Suren
   Baghdasaryan puts the vm_lock back into the vma. Our reasons for
   pulling it out were largely bogus and that change made the code more
   messy. This patchset provides small (0-10%) improvements on one
   microbenchmark.

 - The series "Docs/mm/damon: misc DAMOS filters documentation fixes and
   improves" from SeongJae Park does some maintenance work on the DAMON
   docs.

 - The series "hugetlb/CMA improvements for large systems" from Frank
   van der Linden addresses a pile of issues which have been observed
   when using CMA on large machines.

 - The series "mm/damon: introduce DAMOS filter type for unmapped pages"
   from SeongJae Park enables users of DMAON/DAMOS to filter my the
   page's mapped/unmapped status.

 - The series "zsmalloc/zram: there be preemption" from Sergey
   Senozhatsky teaches zram to run its compression and decompression
   operations preemptibly.

 - The series "selftests/mm: Some cleanups from trying to run them" from
   Brendan Jackman fixes a pile of unrelated issues which Brendan
   encountered while runnimg our selftests.

 - The series "fs/proc/task_mmu: add guard region bit to pagemap" from
   Lorenzo Stoakes permits userspace to use /proc/pid/pagemap to
   determine whether a particular page is a guard page.

 - The series "mm, swap: remove swap slot cache" from Kairui Song
   removes the swap slot cache from the allocation path - it simply
   wasn't being effective.

 - The series "mm: cleanups for device-exclusive entries (hmm)" from
   David Hildenbrand implements a number of unrelated cleanups in this
   code.

 - The series "mm: Rework generic PTDUMP configs" from Anshuman Khandual
   implements a number of preparatoty cleanups to the GENERIC_PTDUMP
   Kconfig logic.

 - The series "mm/damon: auto-tune aggregation interval" from SeongJae
   Park implements a feedback-driven automatic tuning feature for
   DAMON's aggregation interval tuning.

 - The series "Fix lazy mmu mode" from Ryan Roberts fixes some issues in
   powerpc, sparc and x86 lazy MMU implementations. Ryan did this in
   preparation for implementing lazy mmu mode for arm64 to optimize
   vmalloc.

 - The series "mm/page_alloc: Some clarifications for migratetype
   fallback" from Brendan Jackman reworks some commentary to make the
   code easier to follow.

 - The series "page_counter cleanup and size reduction" from Shakeel
   Butt cleans up the page_counter code and fixes a size increase which
   we accidentally added late last year.

 - The series "Add a command line option that enables control of how
   many threads should be used to allocate huge pages" from Thomas
   Prescher does that. It allows the careful operator to significantly
   reduce boot time by tuning the parallalization of huge page
   initialization.

 - The series "Fix calculations in trace_balance_dirty_pages() for cgwb"
   from Tang Yizhou fixes the tracing output from the dirty page
   balancing code.

 - The series "mm/damon: make allow filters after reject filters useful
   and intuitive" from SeongJae Park improves the handling of allow and
   reject filters. Behaviour is made more consistent and the documention
   is updated accordingly.

 - The series "Switch zswap to object read/write APIs" from Yosry Ahmed
   updates zswap to the new object read/write APIs and thus permits the
   removal of some legacy code from zpool and zsmalloc.

 - The series "Some trivial cleanups for shmem" from Baolin Wang does as
   it claims.

 - The series "fs/dax: Fix ZONE_DEVICE page reference counts" from
   Alistair Popple regularizes the weird ZONE_DEVICE page refcount
   handling in DAX, permittig the removal of a number of special-case
   checks.

 - The series "refactor mremap and fix bug" from Lorenzo Stoakes is a
   preparatoty refactoring and cleanup of the mremap() code.

 - The series "mm: MM owner tracking for large folios (!hugetlb) +
   CONFIG_NO_PAGE_MAPCOUNT" from David Hildenbrand reworks the manner in
   which we determine whether a large folio is known to be mapped
   exclusively into a single MM.

 - The series "mm/damon: add sysfs dirs for managing DAMOS filters based
   on handling layers" from SeongJae Park adds a couple of new sysfs
   directories to ease the management of DAMON/DAMOS filters.

 - The series "arch, mm: reduce code duplication in mem_init()" from
   Mike Rapoport consolidates many per-arch implementations of
   mem_init() into code generic code, where that is practical.

 - The series "mm/damon/sysfs: commit parameters online via
   damon_call()" from SeongJae Park continues the cleaning up of sysfs
   access to DAMON internal data.

 - The series "mm: page_ext: Introduce new iteration API" from Luiz
   Capitulino reworks the page_ext initialization to fix a boot-time
   crash which was observed with an unusual combination of compile and
   cmdline options.

 - The series "Buddy allocator like (or non-uniform) folio split" from
   Zi Yan reworks the code to split a folio into smaller folios. The
   main benefit is lessened memory consumption: fewer post-split folios
   are generated.

 - The series "Minimize xa_node allocation during xarry split" from Zi
   Yan reduces the number of xarray xa_nodes which are generated during
   an xarray split.

 - The series "drivers/base/memory: Two cleanups" from Gavin Shan
   performs some maintenance work on the drivers/base/memory code.

 - The series "Add tracepoints for lowmem reserves, watermarks and
   totalreserve_pages" from Martin Liu adds some more tracepoints to the
   page allocator code.

 - The series "mm/madvise: cleanup requests validations and
   classifications" from SeongJae Park cleans up some warts which
   SeongJae observed during his earlier madvise work.

 - The series "mm/hwpoison: Fix regressions in memory failure handling"
   from Shuai Xue addresses two quite serious regressions which Shuai
   has observed in the memory-failure implementation.

 - The series "mm: reliable huge page allocator" from Johannes Weiner
   makes huge page allocations cheaper and more reliable by reducing
   fragmentation.

 - The series "Minor memcg cleanups & prep for memdescs" from Matthew
   Wilcox is preparatory work for the future implementation of memdescs.

 - The series "track memory used by balloon drivers" from Nico Pache
   introduces a way to track memory used by our various balloon drivers.

 - The series "mm/damon: introduce DAMOS filter type for active pages"
   from Nhat Pham permits users to filter for active/inactive pages,
   separately for file and anon pages.

 - The series "Adding Proactive Memory Reclaim Statistics" from Hao Jia
   separates the proactive reclaim statistics from the direct reclaim
   statistics.

 - The series "mm/vmscan: don't try to reclaim hwpoison folio" from
   Jinjiang Tu fixes our handling of hwpoisoned pages within the reclaim
   code.

* tag 'mm-stable-2025-03-30-16-52' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (431 commits)
  mm/page_alloc: remove unnecessary __maybe_unused in order_to_pindex()
  x86/mm: restore early initialization of high_memory for 32-bits
  mm/vmscan: don't try to reclaim hwpoison folio
  mm/hwpoison: introduce folio_contain_hwpoisoned_page() helper
  cgroup: docs: add pswpin and pswpout items in cgroup v2 doc
  mm: vmscan: split proactive reclaim statistics from direct reclaim statistics
  selftests/mm: speed up split_huge_page_test
  selftests/mm: uffd-unit-tests support for hugepages > 2M
  docs/mm/damon/design: document active DAMOS filter type
  mm/damon: implement a new DAMOS filter type for active pages
  fs/dax: don't disassociate zero page entries
  MM documentation: add "Unaccepted" meminfo entry
  selftests/mm: add commentary about 9pfs bugs
  fork: use __vmalloc_node() for stack allocation
  docs/mm: Physical Memory: Populate the "Zones" section
  xen: balloon: update the NR_BALLOON_PAGES state
  hv_balloon: update the NR_BALLOON_PAGES state
  balloon_compaction: update the NR_BALLOON_PAGES state
  meminfo: add a per node counter for balloon drivers
  mm: remove references to folio in __memcg_kmem_uncharge_page()
  ...
2025-04-01 09:29:18 -07:00
Suren BaghdasaryanandAndrew Morton 7f8ceea0c5 refcount: provide ops for cases when object's memory can be reused
For speculative lookups where a successful inc_not_zero() pins the object,
but where we still need to double check if the object acquired is indeed
the one we set out to acquire (identity check), needs this validation to
happen *after* the increment.  Similarly, when a new object is initialized
and its memory might have been previously occupied by another object, all
stores to initialize the object should happen *before* refcount
initialization.

Notably SLAB_TYPESAFE_BY_RCU is one such an example when this ordering is
required for reference counting.

Add refcount_{add|inc}_not_zero_acquire() to guarantee the proper ordering
between acquiring a reference count on an object and performing the
identity check for that object.

Add refcount_set_release() to guarantee proper ordering between stores
initializing object attributes and the store initializing the refcount. 
refcount_set_release() should be done after all other object attributes
are initialized.  Once refcount_set_release() is called, the object should
be considered visible to other tasks even if it was not yet added into an
object collection normally used to discover it.  This is because other
tasks might have discovered the object previously occupying the same
memory and after memory reuse they can succeed in taking refcount for the
new object and start using it.

Object reuse example to consider:

consumer:
    obj = lookup(collection, key);
    if (!refcount_inc_not_zero_acquire(&obj->ref))
        return;
    if (READ_ONCE(obj->key) != key) { /* identity check */
        put_ref(obj);
        return;
    }
    use(obj->value);

                 producer:
                     remove(collection, obj->key);
                     if (!refcount_dec_and_test(&obj->ref))
                         return;
                     obj->key = KEY_INVALID;
                     free(obj);
                     obj = malloc(); /* obj is reused */
                     obj->key = new_key;
                     obj->value = new_value;
                     refcount_set_release(obj->ref, 1);
                     add(collection, new_key, obj);

refcount_{add|inc}_not_zero_acquire() is required to prevent the following
reordering when refcount_inc_not_zero() is used instead:

consumer:
    obj = lookup(collection, key);
    if (READ_ONCE(obj->key) != key) { /* reordered identity check */
        put_ref(obj);
        return;
    }
                 producer:
                     remove(collection, obj->key);
                     if (!refcount_dec_and_test(&obj->ref))
                         return;
                     obj->key = KEY_INVALID;
                     free(obj);
                     obj = malloc(); /* obj is reused */
                     obj->key = new_key;
                     obj->value = new_value;
                     refcount_set_release(obj->ref, 1);
                     add(collection, new_key, obj);

    if (!refcount_inc_not_zero(&obj->ref))
        return;
    use(obj->value); /* USING WRONG OBJECT */

refcount_set_release() is required to prevent the following reordering
when refcount_set() is used instead:

consumer:
    obj = lookup(collection, key);

                 producer:
                     remove(collection, obj->key);
                     if (!refcount_dec_and_test(&obj->ref))
                         return;
                     obj->key = KEY_INVALID;
                     free(obj);
                     obj = malloc(); /* obj is reused */
                     obj->key = new_key; /* new_key == old_key */
                     refcount_set(obj->ref, 1);

    if (!refcount_inc_not_zero_acquire(&obj->ref))
        return;
    if (READ_ONCE(obj->key) != key) { /* pass since new_key == old_key */
        put_ref(obj);
        return;
    }
    use(obj->value); /* USING STALE obj->value */

                     obj->value = new_value; /* reordered store */
                     add(collection, key, obj);

[surenb@google.com: fix title underlines in refcount-vs-atomic.rst]
  Link: https://lkml.kernel.org/r/20250217161645.3137927-1-surenb@google.com
Link: https://lkml.kernel.org/r/20250213224655.1680278-11-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>	[slab]
Tested-by: Shivank Garg <shivankg@amd.com>
  Link: https://lkml.kernel.org/r/5e19ec93-8307-47c2-bb13-3ddf7150624e@amd.com
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Klara Modin <klarasmodin@gmail.com>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Sourav Panda <souravpanda@google.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2025-03-16 22:06:19 -07:00
Paul E. McKenneyandBoqun Feng 73298c7cf1 rcu: Remove references to old grace-period-wait primitives
The rcu_barrier_sched(), synchronize_sched(), and synchronize_rcu_bh()
RCU API members have been gone for many years.  This commit therefore
removes non-historical instances of them.

Reported-by: Joe Perches <joe@perches.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
2025-02-04 21:50:06 -08:00
Paul E. McKenneyandBoqun Feng bea1d19f03 doc: Add broken-timing possibility to stallwarn.rst
Currently, stallwarn.rst does not mention the fact that timer bugs can
result in false-positive RCU CPU stall warnings.  This commit therefore
adds this to the list.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
2025-02-04 21:50:06 -08:00
Baruch SiachandFrederic Weisbecker 4a09e35892 doc: rcu: update printed dynticks counter bits
The stall warning prints 16 bits since commit 171476775d
("context_tracking: Convert state to atomic_t").

Fixes: 171476775d ("context_tracking: Convert state to atomic_t")
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
2024-11-12 21:40:24 +01:00