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, 98 insertions, 0 deletions

diff --git a/tools/docs/features-refresh.sh b/tools/docs/features-refresh.sh
new file mode 100755
index 000000000..c2288124e
--- /dev/null
+++ b/tools/docs/features-refresh.sh
@@ -0,0 +1,98 @@
+#
+# Small script that refreshes the kernel feature support status in place.
+#
+
+for F_FILE in Documentation/features/*/*/arch-support.txt; do
+	F=$(grep "^#         Kconfig:" "$F_FILE" | cut -c26-)
+
+	#
+	# Each feature F is identified by a pair (O, K), where 'O' can
+	# be either the empty string (for 'nop') or "not" (the logical
+	# negation operator '!'); other operators are not supported.
+	#
+	O=""
+	K=$F
+	if [[ "$F" == !* ]]; then
+		O="not"
+		K=$(echo $F | sed -e 's/^!//g')
+	fi
+
+	#
+	# F := (O, K) is 'valid' iff there is a Kconfig file (for some
+	# arch) which contains K.
+	#
+	# Notice that this definition entails an 'asymmetry' between
+	# the case 'O = ""' and the case 'O = "not"'. E.g., F may be
+	# _invalid_ if:
+	#
+	# [case 'O = ""']
+	#   1) no arch provides support for F,
+	#   2) K does not exist (e.g., it was renamed/mis-typed);
+	#
+	# [case 'O = "not"']
+	#   3) all archs provide support for F,
+	#   4) as in (2).
+	#
+	# The rationale for adopting this definition (and, thus, for
+	# keeping the asymmetry) is:
+	#
+	#       We want to be able to 'detect' (2) (or (4)).
+	#
+	# (1) and (3) may further warn the developers about the fact
+	# that K can be removed.
+	#
+	F_VALID="false"
+	for ARCH_DIR in arch/*/; do
+		K_FILES=$(find $ARCH_DIR -name "Kconfig*")
+		K_GREP=$(grep "$K" $K_FILES)
+		if [ ! -z "$K_GREP" ]; then
+			F_VALID="true"
+			break
+		fi
+	done
+	if [ "$F_VALID" = "false" ]; then
+		printf "WARNING: '%s' is not a valid Kconfig\n" "$F"
+	fi
+
+	T_FILE="$F_FILE.tmp"
+	grep "^#" $F_FILE > $T_FILE
+	echo "    -----------------------" >> $T_FILE
+	echo "    |         arch |status|" >> $T_FILE
+	echo "    -----------------------" >> $T_FILE
+	for ARCH_DIR in arch/*/; do
+		ARCH=$(echo $ARCH_DIR | sed -e 's/^arch//g' | sed -e 's/\///g')
+		K_FILES=$(find $ARCH_DIR -name "Kconfig*")
+		K_GREP=$(grep "$K" $K_FILES)
+		#
+		# Arch support status values for (O, K) are updated according
+		# to the following rules.
+		#
+		#   - ("", K) is 'supported by a given arch', if there is a
+		#     Kconfig file for that arch which contains K;
+		#
+		#   - ("not", K) is 'supported by a given arch', if there is
+		#     no Kconfig file for that arch which contains K;
+		#
+		#   - otherwise: preserve the previous status value (if any),
+		#                default to 'not yet supported'.
+		#
+		# Notice that, according these rules, invalid features may be
+		# updated/modified.
+		#
+		if [ "$O" = "" ] && [ ! -z "$K_GREP" ]; then
+			printf "    |%12s: |  ok  |\n" "$ARCH" >> $T_FILE
+		elif [ "$O" = "not" ] && [ -z "$K_GREP" ]; then
+			printf "    |%12s: |  ok  |\n" "$ARCH" >> $T_FILE
+		else
+			S=$(grep -v "^#" "$F_FILE" | grep " $ARCH:")
+			if [ ! -z "$S" ]; then
+				echo "$S" >> $T_FILE
+			else
+				printf "    |%12s: | TODO |\n" "$ARCH" \
+					>> $T_FILE
+			fi
+		fi
+	done
+	echo "    -----------------------" >> $T_FILE
+	mv $T_FILE $F_FILE
+done