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, 115 insertions, 0 deletions

diff --git a/Documentation/Makefile b/Documentation/Makefile
new file mode 100644
index 000000000..377a44965
--- /dev/null
+++ b/Documentation/Makefile
@@ -0,0 +1,115 @@
+# -*- makefile -*-
+# Makefile for Sphinx documentation
+#
+
+# for cleaning
+subdir- := devicetree/bindings
+
+ifneq ($(MAKECMDGOALS),cleandocs)
+# Check for broken documentation file references
+ifeq ($(CONFIG_WARN_MISSING_DOCUMENTS),y)
+$(shell $(srctree)/tools/docs/documentation-file-ref-check --warn)
+endif
+
+# Check for broken ABI files
+ifeq ($(CONFIG_WARN_ABI_ERRORS),y)
+$(shell $(srctree)/tools/docs/get_abi.py --dir $(srctree)/Documentation/ABI validate)
+endif
+endif
+
+# You can set these variables from the command line.
+SPHINXBUILD   = sphinx-build
+SPHINXOPTS    =
+SPHINXDIRS    = .
+DOCS_THEME    =
+DOCS_CSS      =
+RUSTDOC       =
+PAPER         =
+BUILDDIR      = $(obj)/output
+PDFLATEX      = xelatex
+LATEXOPTS     = -interaction=batchmode -no-shell-escape
+
+PYTHONPYCACHEPREFIX ?= $(abspath $(BUILDDIR)/__pycache__)
+
+# Wrapper for sphinx-build
+
+BUILD_WRAPPER = $(srctree)/tools/docs/sphinx-build-wrapper
+
+# For denylisting "variable font" files
+# Can be overridden by setting as an env variable
+FONTS_CONF_DENY_VF ?= $(HOME)/deny-vf
+
+# User-friendly check for sphinx-build
+HAVE_SPHINX := $(shell if which $(SPHINXBUILD) >/dev/null 2>&1; then echo 1; else echo 0; fi)
+
+ifeq ($(HAVE_SPHINX),0)
+
+.DEFAULT:
+	$(warning The '$(SPHINXBUILD)' command was not found. Make sure you have Sphinx installed and in PATH, or set the SPHINXBUILD make variable to point to the full path of the '$(SPHINXBUILD)' executable.)
+	@echo
+	@$(srctree)/tools/docs/sphinx-pre-install
+	@echo "  SKIP    Sphinx $@ target."
+
+else # HAVE_SPHINX
+
+# Common documentation targets
+htmldocs mandocs infodocs texinfodocs latexdocs epubdocs xmldocs pdfdocs linkcheckdocs:
+	$(Q)PYTHONPYCACHEPREFIX="$(PYTHONPYCACHEPREFIX)" \
+		$(srctree)/tools/docs/sphinx-pre-install --version-check
+	+$(Q)PYTHONPYCACHEPREFIX="$(PYTHONPYCACHEPREFIX)" \
+		$(PYTHON3) $(BUILD_WRAPPER) $@ \
+		--sphinxdirs="$(SPHINXDIRS)" $(RUSTDOC) \
+		--builddir="$(BUILDDIR)" --deny-vf=$(FONTS_CONF_DENY_VF) \
+		--theme=$(DOCS_THEME) --css=$(DOCS_CSS) --paper=$(PAPER)
+
+
+endif
+
+# The following targets are independent of HAVE_SPHINX, and the rules should
+# work or silently pass without Sphinx.
+
+htmldocs-redirects: $(srctree)/Documentation/.renames.txt
+	@tools/docs/gen-redirects.py --output $(BUILDDIR) < $<
+
+refcheckdocs:
+	$(Q)cd $(srctree); tools/docs/documentation-file-ref-check
+
+cleandocs:
+	$(Q)rm -rf $(BUILDDIR)
+
+# Used only on help
+_SPHINXDIRS   = $(shell printf "%s\n" $(patsubst $(srctree)/Documentation/%/index.rst,%,$(wildcard $(srctree)/Documentation/*/index.rst)) | sort -f)
+
+dochelp:
+	@echo  ' Linux kernel internal documentation in different formats from ReST:'
+	@echo  '  htmldocs        - HTML'
+	@echo  '  htmldocs-redirects - generate HTML redirects for moved pages'
+	@echo  '  texinfodocs     - Texinfo'
+	@echo  '  infodocs        - Info'
+	@echo  '  mandocs         - Man pages'
+	@echo  '  latexdocs       - LaTeX'
+	@echo  '  pdfdocs         - PDF'
+	@echo  '  epubdocs        - EPUB'
+	@echo  '  xmldocs         - XML'
+	@echo  '  linkcheckdocs   - check for broken external links'
+	@echo  '                    (will connect to external hosts)'
+	@echo  '  refcheckdocs    - check for references to non-existing files under'
+	@echo  '                    Documentation'
+	@echo  '  cleandocs       - clean all generated files'
+	@echo
+	@echo  '  make SPHINXDIRS="s1 s2" [target] Generate only docs of folder s1, s2'
+	@echo  '  top level values for SPHINXDIRS are:'
+	@echo  '$(_SPHINXDIRS)' | fmt -s -w 75 -g 75 | sed 's/^/    /'
+	@echo  '  you may also use a subdirectory like SPHINXDIRS=userspace-api/media,'
+	@echo  '  provided that there is an index.rst file at the subdirectory.'
+	@echo
+	@echo  '  make DOCS_THEME={sphinx-theme} selects a different Sphinx theme.'
+	@echo
+	@echo  '  make DOCS_CSS={a .css file} adds a DOCS_CSS override file for html/epub output.'
+	@echo
+	@echo  '  make PAPER={a4|letter} Specifies the paper size used for LaTeX/PDF output.'
+	@echo
+	@echo  '  make FONTS_CONF_DENY_VF={path} sets a deny list to block variable Noto CJK fonts'
+	@echo  '  for PDF build. See tools/lib/python/kdoc/latex_fonts.py for more details'
+	@echo
+	@echo  '  Default location for the generated documents is Documentation/output'