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, 45 insertions, 0 deletions

diff --git a/Documentation/admin-guide/mm/index.rst b/Documentation/admin-guide/mm/index.rst
new file mode 100644
index 000000000..bbb563cba
--- /dev/null
+++ b/Documentation/admin-guide/mm/index.rst
@@ -0,0 +1,45 @@
+=================
+Memory Management
+=================
+
+Linux memory management subsystem is responsible, as the name implies,
+for managing the memory in the system. This includes implementation of
+virtual memory and demand paging, memory allocation both for kernel
+internal structures and user space programs, mapping of files into
+processes address space and many other cool things.
+
+Linux memory management is a complex system with many configurable
+settings. Most of these settings are available via ``/proc``
+filesystem and can be queried and adjusted using ``sysctl``. These APIs
+are described in Documentation/admin-guide/sysctl/vm.rst and in `man 5 proc`_.
+
+.. _man 5 proc: http://man7.org/linux/man-pages/man5/proc.5.html
+
+Linux memory management has its own jargon and if you are not yet
+familiar with it, consider reading Documentation/admin-guide/mm/concepts.rst.
+
+Here we document in detail how to interact with various mechanisms in
+the Linux memory management.
+
+.. toctree::
+   :maxdepth: 1
+
+   concepts
+   cma_debugfs
+   damon/index
+   hugetlbpage
+   idle_page_tracking
+   ksm
+   memory-hotplug
+   multigen_lru
+   nommu-mmap
+   numa_memory_policy
+   numaperf
+   pagemap
+   shrinker_debugfs
+   slab
+   soft-dirty
+   transhuge
+   userfaultfd
+   zswap
+   kho