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, 50 insertions, 0 deletions

diff --git a/Documentation/driver-api/firewire.rst b/Documentation/driver-api/firewire.rst
new file mode 100644
index 000000000..28a32410f
--- /dev/null
+++ b/Documentation/driver-api/firewire.rst
@@ -0,0 +1,50 @@
+===========================================
+Firewire (IEEE 1394) driver Interface Guide
+===========================================
+
+Introduction and Overview
+=========================
+
+The Linux FireWire subsystem adds some interfaces into the Linux system to
+ use/maintain+any resource on IEEE 1394 bus.
+
+The main purpose of these interfaces is to access address space on each node
+on IEEE 1394 bus by ISO/IEC 13213 (IEEE 1212) procedure, and to control
+isochronous resources on the bus by IEEE 1394 procedure.
+
+Two types of interfaces are added, according to consumers of the interface. A
+set of userspace interfaces is available via `firewire character devices`. A set
+of kernel interfaces is available via exported symbols in `firewire-core` module.
+
+Firewire char device data structures
+====================================
+
+.. include:: ../ABI/stable/firewire-cdev
+    :literal:
+
+.. kernel-doc:: include/uapi/linux/firewire-cdev.h
+    :internal:
+
+Firewire device probing and sysfs interfaces
+============================================
+
+.. include:: ../ABI/stable/sysfs-bus-firewire
+    :literal:
+
+.. kernel-doc:: drivers/firewire/core-device.c
+    :export:
+
+Firewire core transaction interfaces
+====================================
+
+.. kernel-doc:: drivers/firewire/core-transaction.c
+    :export:
+
+Firewire Isochronous I/O interfaces
+===================================
+
+.. kernel-doc:: include/linux/firewire.h
+   :functions: fw_iso_context_schedule_flush_completions
+.. kernel-doc:: drivers/firewire/core-iso.c
+   :export:
+