Merge branches 'expcb.2026.07.24a', 'misc.2026.07.30a', 'rcu-tasks.2026.07.30a', 'srcu.2026.08.11a' and 'torture.2026.08.14a' into HEADgrafted

Changes:

Make expedited grace periods expedite normal RCU callbacks

Miscellaneous fixes:
 * Improve diagnostic output with character task states.
 * Mark accesses to inform KCSAN of concurrency design.
 * Move from kmalloc() to kmalloc_obj().
 * Documentation updates.
 * Improve handling of RCU deferred quiescent states.
 * Clean up unused function arguments and structure fields.
 * Reduce show_rcu_gp_kthreads() stack space.

Tasks RCU updates:
 * Clean up after SRCU re-implementation of Tasks Trace RCU.
 * Mark accesses to inform KCSAN of concurrency design.
 * Add ->lazy_timer status to diagnostic output.
 * Remove an unnecessary memory barrier.
 * Fix a data race, courtesy of KCSAN.
 * Documentation updates.
 * Convert cond_resched_tasks_rcu_qs() from macro to static inline
   function.

SRCU updates:
 * Add Rust helpers for SRCU.
 * Avoid losing queued work at cleanup_srcu_struct() time.

Torture-test updates:
 * Preparation work for immediate RCU priority deboosting.
 * Test RCU readers from real interrupt handlers (as opposed to softirq).
 * Simplify code through use of cpumask_next_wrap().
 * Improve diagnostic output with character task states.
 * Add rcutorture.nwriters parameter to allow lightweight stall testing,
   and rcutorture.stall_only to make doing so easier.
 * Test an RCU Tasks Trace grace period implying an RCU grace period.
 * Make RCU Tasks Trace torturing track reader batches.
 * Fix a data race, courtesy of KCSAN.
 * Plug a shuffle_tmp_mask memory leak on kthread spawn failure.

1 files changed, 165 insertions, 0 deletions

diff --git a/Documentation/crypto/libcrypto.rst b/Documentation/crypto/libcrypto.rst
new file mode 100644
index 000000000..a1557d45b
--- /dev/null
+++ b/Documentation/crypto/libcrypto.rst
@@ -0,0 +1,165 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+==============
+Crypto library
+==============
+
+``lib/crypto/`` provides faster and easier access to cryptographic algorithms
+than the traditional crypto API.
+
+Each cryptographic algorithm is supported via a set of dedicated functions.
+"Crypto agility", where needed, is left to calling code.
+
+The crypto library functions are intended to be boring and straightforward, and
+to follow familiar conventions.  Their primary documentation is their (fairly
+extensive) kernel-doc.  This page just provides some extra high-level context.
+
+Note that the crypto library isn't entirely new.  ``lib/`` has contained some
+crypto functions since 2005.  Rather, it's just an approach that's been expanded
+over time as it's been found to work well.  It also largely just matches how the
+kernel already does things elsewhere.
+
+Scope and intended audience
+===========================
+
+The crypto library documentation is primarily meant for kernel developers who
+need to use a particular cryptographic algorithm(s) in kernel code.  For
+example, "I just need to compute a SHA-256 hash."  A secondary audience is
+developers working on the crypto algorithm implementations themselves.
+
+If you're looking for more general information about cryptography, like the
+differences between the different crypto algorithms or how to select an
+appropriate algorithm, you should refer to external sources which cover that
+type of information much more comprehensively.  If you need help selecting
+algorithms for a new kernel feature that doesn't already have its algorithms
+predefined, please reach out to ``linux-crypto@vger.kernel.org`` for advice.
+
+Code organization
+=================
+
+- ``lib/crypto/*.c``: the crypto algorithm implementations
+
+- ``lib/crypto/$(SRCARCH)/``: architecture-specific code for crypto algorithms.
+  It is here rather than somewhere in ``arch/`` partly because this allows
+  generic and architecture-optimized code to be easily built into a single
+  loadable module (when the algorithm is set to 'm' in the kconfig).
+
+- ``lib/crypto/tests/``: KUnit tests for the crypto algorithms
+
+- ``include/crypto/``: crypto headers, for both the crypto library and the
+  traditional crypto API
+
+Generally, there is one kernel module per algorithm.  Sometimes related
+algorithms are grouped into one module.  There is intentionally no common
+framework, though there are some utility functions that multiple algorithms use.
+
+Each algorithm module is controlled by a tristate kconfig symbol
+``CRYPTO_LIB_$(ALGORITHM)``.  As is the norm for library functions in the
+kernel, these are hidden symbols which don't show up in the kconfig menu.
+Instead, they are just selected by all the kconfig symbols that need them.
+
+Many of the algorithms have multiple implementations: a generic implementation
+and architecture-optimized implementation(s).  Each module initialization
+function, or initcall in the built-in case, automatically enables the best
+implementation based on the available CPU features.
+
+Note that the crypto library doesn't use the ``crypto/``,
+``arch/$(SRCARCH)/crypto/``, or ``drivers/crypto/`` directories.  These
+directories are used by the traditional crypto API.  When possible, algorithms
+in the traditional crypto API are implemented by calls into the library.
+
+Advantages
+==========
+
+Some of the advantages of the library over the traditional crypto API are:
+
+- The library functions tend to be much easier to use.  For example, a hash
+  value can be computed using only a single function call.  Most of the library
+  functions always succeed and return void, eliminating the need to write
+  error-handling code.  Most also accept standard virtual addresses, rather than
+  scatterlists which are difficult and less efficient to work with.
+
+- The library functions are usually faster, especially for short inputs.  They
+  call the crypto algorithms directly without inefficient indirect calls, memory
+  allocations, string parsing, lookups in an algorithm registry, and other
+  unnecessary API overhead.  Architecture-optimized code is enabled by default.
+
+- The library functions use standard link-time dependencies instead of
+  error-prone dynamic loading by name.  There's no need for workarounds such as
+  forcing algorithms to be built-in or adding module soft dependencies.
+
+- The library focuses on the approach that works the best on the vast majority
+  of systems: CPU-based implementations of the crypto algorithms, utilizing
+  on-CPU acceleration (such as AES instructions) when available.
+
+- The library uses standard KUnit tests, rather than custom ad-hoc tests.
+
+- The library tends to have higher assurance implementations of the crypto
+  algorithms.  This is both due to its simpler design and because more of its
+  code is being regularly tested.
+
+- The library supports features that don't fit into the rigid framework of the
+  traditional crypto API, for example interleaved hashing and XOFs.
+
+When to use it
+==============
+
+In-kernel users should use the library (rather than the traditional crypto API)
+whenever possible.  Many subsystems have already been converted.  It usually
+simplifies their code significantly and improves performance.
+
+Some kernel features allow userspace to provide an arbitrary string that selects
+an arbitrary algorithm from the traditional crypto API by name.  These features
+generally will have to keep using the traditional crypto API for backwards
+compatibility.
+
+Note: new kernel features shouldn't support every algorithm, but rather make a
+deliberate choice about what algorithm(s) to support.  History has shown that
+making a deliberate, thoughtful choice greatly simplifies code maintenance,
+reduces the chance for mistakes (such as using an obsolete, insecure, or
+inappropriate algorithm), and makes your feature easier to use.
+
+Testing
+=======
+
+The crypto library uses standard KUnit tests.  Like many of the kernel's other
+KUnit tests, they are included in the set of tests that is run by
+``tools/testing/kunit/kunit.py run --alltests``.
+
+A ``.kunitconfig`` file is also provided to run just the crypto library tests.
+For example, here's how to run them in user-mode Linux:
+
+.. code-block:: sh
+
+    tools/testing/kunit/kunit.py run --kunitconfig=lib/crypto/
+
+Many of the crypto algorithms have architecture-optimized implementations.
+Testing those requires building an appropriate kernel and running the tests
+either in QEMU or on appropriate hardware.  Here's one example with QEMU:
+
+.. code-block:: sh
+
+    tools/testing/kunit/kunit.py run --kunitconfig=lib/crypto/ --arch=arm64 --make_options LLVM=1
+
+Depending on the code being tested, flags may need to be passed to QEMU to
+emulate the correct type of hardware for the code to be reached.
+
+Since correctness is essential in cryptographic code, new architecture-optimized
+code is accepted only if it can be tested in QEMU.
+
+Note: the crypto library also includes FIPS 140 self-tests.  These are
+lightweight, are designed specifically to meet FIPS 140 requirements, and exist
+*only* to meet those requirements.  Normal testing done by kernel developers and
+integrators should use the much more comprehensive KUnit tests instead.
+
+API documentation
+=================
+
+.. toctree::
+   :maxdepth: 2
+
+   libcrypto-blockcipher
+   libcrypto-hash
+   libcrypto-signature
+   libcrypto-utils
+   sha3