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, 55 insertions, 0 deletions

diff --git a/Documentation/driver-api/media/index.rst b/Documentation/driver-api/media/index.rst
new file mode 100644
index 000000000..08fc2cfc0
--- /dev/null
+++ b/Documentation/driver-api/media/index.rst
@@ -0,0 +1,55 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+.. include:: <isonum.txt>
+
+===================================
+Media subsystem kernel internal API
+===================================
+
+This section contains usage information about media subsystem and
+its supported drivers.
+
+Please see:
+
+Documentation/admin-guide/media/index.rst
+
+  - for usage information about media subsystem and supported drivers;
+
+Documentation/userspace-api/media/index.rst
+
+  - for the userspace APIs used on media devices.
+
+
+.. toctree::
+    :caption: Table of Contents
+    :maxdepth: 5
+    :numbered:
+
+    maintainer-entry-profile
+    media-committers
+
+    v4l2-core
+    dtv-core
+    rc-core
+    mc-core
+    cec-core
+    tx-rx
+    camera-sensor
+
+    drivers/index
+
+**Copyright** |copy| 2009-2020 : LinuxTV Developers
+
+::
+
+  This documentation is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by the Free
+  Software Foundation; either version 2 of the License, or (at your option) any
+  later version.
+
+  This program is distributed in the hope that it will be useful, but WITHOUT
+  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+  more details.
+
+  For more details see the file COPYING in the source distribution of Linux.