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, 107 insertions, 0 deletions

diff --git a/Documentation/admin-guide/sysctl/index.rst b/Documentation/admin-guide/sysctl/index.rst
new file mode 100644
index 000000000..50f00514f
--- /dev/null
+++ b/Documentation/admin-guide/sysctl/index.rst
@@ -0,0 +1,107 @@
+===========================
+Documentation for /proc/sys
+===========================
+
+Copyright (c) 1998, 1999,  Rik van Riel <riel@nl.linux.org>
+
+------------------------------------------------------------------------------
+
+'Why', I hear you ask, 'would anyone even _want_ documentation
+for them sysctl files? If anybody really needs it, it's all in
+the source...'
+
+Well, this documentation is written because some people either
+don't know they need to tweak something, or because they don't
+have the time or knowledge to read the source code.
+
+Furthermore, the programmers who built sysctl have built it to
+be actually used, not just for the fun of programming it :-)
+
+------------------------------------------------------------------------------
+
+Legal blurb:
+
+As usual, there are two main things to consider:
+
+1. you get what you pay for
+2. it's free
+
+The consequences are that I won't guarantee the correctness of
+this document, and if you come to me complaining about how you
+screwed up your system because of wrong documentation, I won't
+feel sorry for you. I might even laugh at you...
+
+But of course, if you _do_ manage to screw up your system using
+only the sysctl options used in this file, I'd like to hear of
+it. Not only to have a great laugh, but also to make sure that
+you're the last RTFMing person to screw up.
+
+In short, e-mail your suggestions, corrections and / or horror
+stories to: <riel@nl.linux.org>
+
+Rik van Riel.
+
+--------------------------------------------------------------
+
+Introduction
+============
+
+Sysctl is a means of configuring certain aspects of the kernel
+at run-time, and the /proc/sys/ directory is there so that you
+don't even need special tools to do it!
+In fact, there are only four things needed to use these config
+facilities:
+
+- a running Linux system
+- root access
+- common sense (this is especially hard to come by these days)
+- knowledge of what all those values mean
+
+As a quick 'ls /proc/sys' will show, the directory consists of
+several (arch-dependent?) subdirs. Each subdir is mainly about
+one part of the kernel, so you can do configuration on a piece
+by piece basis, or just some 'thematic frobbing'.
+
+This documentation is about:
+
+=============== ===============================================================
+abi/		execution domains & personalities
+<$ARCH>		tuning controls for various CPU architecture (e.g. csky, s390)
+crypto/		cryptographic subsystem
+debug/		debugging features
+dev/		device specific information (e.g. dev/cdrom/info)
+fs/		specific filesystems
+		filehandle, inode, dentry and quota tuning
+		binfmt_misc <Documentation/admin-guide/binfmt-misc.rst>
+kernel/		global kernel info / tuning
+		miscellaneous stuff
+		some architecture-specific controls
+		security (LSM) stuff
+net/		networking stuff, for documentation look in:
+		<Documentation/networking/>
+proc/		<empty>
+sunrpc/		SUN Remote Procedure Call (NFS)
+user/		Per user namespace limits
+vm/		memory management tuning
+		buffer and cache management
+xen/		Xen hypervisor controls
+=============== ===============================================================
+
+These are the subdirs I have on my system or have been discovered by
+searching through the source code. There might be more or other subdirs
+in another setup. If you see another dir, I'd really like to hear about
+it :-)
+
+.. toctree::
+   :maxdepth: 1
+
+   abi
+   crypto
+   debug
+   fs
+   kernel
+   net
+   sunrpc
+   user
+   vm
+   xen