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, 75 insertions, 0 deletions

diff --git a/Documentation/firmware-guide/acpi/aml-debugger.rst b/Documentation/firmware-guide/acpi/aml-debugger.rst
new file mode 100644
index 000000000..a889d43bc
--- /dev/null
+++ b/Documentation/firmware-guide/acpi/aml-debugger.rst
@@ -0,0 +1,75 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
+================
+The AML Debugger
+================
+
+:Copyright: |copy| 2016, Intel Corporation
+:Author: Lv Zheng <lv.zheng@intel.com>
+
+
+This document describes the usage of the AML debugger embedded in the Linux
+kernel.
+
+1. Build the debugger
+=====================
+
+The following kernel configuration items are required to enable the AML
+debugger interface from the Linux kernel::
+
+   CONFIG_ACPI_DEBUGGER=y
+   CONFIG_ACPI_DEBUGGER_USER=m
+
+The userspace utilities can be built from the kernel source tree using
+the following commands::
+
+   $ cd tools
+   $ make acpi
+
+The resultant userspace tool binary is then located at::
+
+   tools/power/acpi/acpidbg
+
+It can be installed to system directories by running "make install" (as a
+sufficiently privileged user).
+
+2. Start the userspace debugger interface
+=========================================
+
+After booting the kernel with the debugger built-in, the debugger can be
+started by using the following commands::
+
+   # mount -t debugfs none /sys/kernel/debug
+   # modprobe acpi_dbg
+   # tools/power/acpi/acpidbg
+
+That spawns the interactive AML debugger environment where you can execute
+debugger commands.
+
+The commands are documented in the "ACPICA Overview and Programmer Reference"
+that can be downloaded from
+
+https://acpica.org/documentation
+
+The detailed debugger commands reference is located in Chapter 12 "ACPICA
+Debugger Reference".  The "help" command can be used for a quick reference.
+
+3. Stop the userspace debugger interface
+========================================
+
+The interactive debugger interface can be closed by pressing Ctrl+C or using
+the "quit" or "exit" commands.  When finished, unload the module with::
+
+   # rmmod acpi_dbg
+
+The module unloading may fail if there is an acpidbg instance running.
+
+4. Run the debugger in a script
+===============================
+
+It may be useful to run the AML debugger in a test script. "acpidbg" supports
+this in a special "batch" mode.  For example, the following command outputs
+the entire ACPI namespace::
+
+   # acpidbg -b "namespace"