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, 23 insertions, 0 deletions

diff --git a/Documentation/driver-api/wmi.rst b/Documentation/driver-api/wmi.rst
new file mode 100644
index 000000000..b847bcdcb
--- /dev/null
+++ b/Documentation/driver-api/wmi.rst
@@ -0,0 +1,23 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+==============
+WMI Driver API
+==============
+
+The WMI driver core supports a more modern bus-based interface for interacting
+with WMI devices, and an older GUID-based interface. The latter interface is
+considered to be deprecated, so new WMI drivers should generally avoid it since
+it has some issues with multiple WMI devices sharing the same GUID.
+The modern bus-based interface instead maps each WMI device to a
+:c:type:`struct wmi_device <wmi_device>`, so it supports WMI devices sharing the
+same GUID. Drivers can then register a :c:type:`struct wmi_driver <wmi_driver>`
+which will be bound to compatible WMI devices by the driver core.
+
+.. kernel-doc:: include/linux/wmi.h
+   :internal:
+
+.. kernel-doc:: drivers/platform/wmi/string.c
+   :export:
+
+.. kernel-doc:: drivers/platform/wmi/core.c
+   :export: