ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

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'