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, 41 insertions, 0 deletions

diff --git a/drivers/mcb/Kconfig b/drivers/mcb/Kconfig
new file mode 100644
index 000000000..0a883486f
--- /dev/null
+++ b/drivers/mcb/Kconfig
@@ -0,0 +1,41 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# MEN Chameleon Bus (MCB) support
+#
+
+menuconfig MCB
+	   tristate "MCB support"
+	   default n
+	   depends on HAS_IOMEM
+	   help
+
+	   The MCB (MEN Chameleon Bus) is a Bus specific to MEN Mikroelektronik
+	   FPGA based devices. It is used to identify MCB based IP-Cores within
+	   an FPGA and provide the necessary framework for instantiating drivers
+	   for these devices.
+
+	   If build as a module, the module is called mcb.ko
+
+if MCB
+config MCB_PCI
+	   tristate "PCI based MCB carrier"
+	   default n
+	   depends on PCI
+	   help
+
+	   This is a MCB carrier on a PCI device. Both PCI attached on-board
+	   FPGAs as well as CompactPCI attached MCB FPGAs are supported with
+	   this driver.
+
+	   If build as a module, the module is called mcb-pci.ko
+
+config MCB_LPC
+	   tristate "LPC (non PCI) based MCB carrier"
+	   default n
+	   help
+
+	   This is a MCB carrier on a LPC or non PCI device.
+
+	   If build as a module, the module is called mcb-lpc.ko
+
+endif # MCB