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, 129 insertions, 0 deletions

diff --git a/Documentation/PCI/endpoint/pci-vntb-function.rst b/Documentation/PCI/endpoint/pci-vntb-function.rst
new file mode 100644
index 000000000..0c51f53ab
--- /dev/null
+++ b/Documentation/PCI/endpoint/pci-vntb-function.rst
@@ -0,0 +1,129 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=================
+PCI vNTB Function
+=================
+
+:Author: Frank Li <Frank.Li@nxp.com>
+
+The difference between PCI NTB function and PCI vNTB function is
+
+PCI NTB function need at two endpoint instances and connect HOST1
+and HOST2.
+
+PCI vNTB function only use one host and one endpoint(EP), use NTB
+connect EP and PCI host
+
+.. code-block:: text
+
+
+  +------------+         +---------------------------------------+
+  |            |         |                                       |
+  +------------+         |                        +--------------+
+  | NTB        |         |                        | NTB          |
+  | NetDev     |         |                        | NetDev       |
+  +------------+         |                        +--------------+
+  | NTB        |         |                        | NTB          |
+  | Transfer   |         |                        | Transfer     |
+  +------------+         |                        +--------------+
+  |            |         |                        |              |
+  |  PCI NTB   |         |                        |              |
+  |    EPF     |         |                        |              |
+  |   Driver   |         |                        | PCI Virtual  |
+  |            |         +---------------+        | NTB Driver   |
+  |            |         | PCI EP NTB    |<------>|              |
+  |            |         |  FN Driver    |        |              |
+  +------------+         +---------------+        +--------------+
+  |            |         |               |        |              |
+  |  PCI BUS   | <-----> |  PCI EP BUS   |        |  Virtual PCI |
+  |            |  PCI    |               |        |     BUS      |
+  +------------+         +---------------+--------+--------------+
+      PCI RC                        PCI EP
+
+Constructs used for Implementing vNTB
+=====================================
+
+	1) Config Region
+	2) Self Scratchpad Registers
+	3) Peer Scratchpad Registers
+	4) Doorbell (DB) Registers
+	5) Memory Window (MW)
+
+
+Config Region:
+--------------
+
+It is same as PCI NTB Function driver
+
+Scratchpad Registers:
+---------------------
+
+It is appended after Config region.
+
+.. code-block:: text
+
+
+  +--------------------------------------------------+ Base
+  |                                                  |
+  |                                                  |
+  |                                                  |
+  |          Common Config Register                  |
+  |                                                  |
+  |                                                  |
+  |                                                  |
+  +-----------------------+--------------------------+ Base + span_offset
+  |                       |                          |
+  |    Peer Span Space    |    Span Space            |
+  |                       |                          |
+  |                       |                          |
+  +-----------------------+--------------------------+ Base + span_offset
+  |                       |                          |      + span_count * 4
+  |                       |                          |
+  |     Span Space        |   Peer Span Space        |
+  |                       |                          |
+  +-----------------------+--------------------------+
+        Virtual PCI             Pcie Endpoint
+        NTB Driver               NTB Driver
+
+
+Doorbell Registers:
+-------------------
+
+  Doorbell Registers are used by the hosts to interrupt each other.
+
+Memory Window:
+--------------
+
+  Actual transfer of data between the two hosts will happen using the
+  memory window.
+
+Modeling Constructs:
+====================
+
+32-bit BARs.
+
+======  ===============
+BAR NO  CONSTRUCTS USED
+======  ===============
+BAR0    Config Region
+BAR1    Doorbell
+BAR2    Memory Window 1
+BAR3    Memory Window 2
+BAR4    Memory Window 3
+BAR5    Memory Window 4
+======  ===============
+
+64-bit BARs.
+
+======  ===============================
+BAR NO  CONSTRUCTS USED
+======  ===============================
+BAR0    Config Region + Scratchpad
+BAR1
+BAR2    Doorbell
+BAR3
+BAR4    Memory Window 1
+BAR5
+======  ===============================
+
+