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, 46 insertions, 0 deletions

diff --git a/drivers/iio/dummy/Kconfig b/drivers/iio/dummy/Kconfig
new file mode 100644
index 000000000..1f46cb9e5
--- /dev/null
+++ b/drivers/iio/dummy/Kconfig
@@ -0,0 +1,46 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Industrial I/O subsystem Dummy Driver configuration
+#
+menu "IIO dummy driver"
+	depends on IIO
+
+config IIO_DUMMY_EVGEN
+	select IRQ_SIM
+	tristate
+
+config IIO_SIMPLE_DUMMY
+	tristate "An example driver with no hardware requirements"
+	depends on IIO_SW_DEVICE
+	help
+	  Driver intended mainly as documentation for how to write
+	  a driver. May also be useful for testing userspace code
+	  without hardware.
+
+if IIO_SIMPLE_DUMMY
+
+config IIO_SIMPLE_DUMMY_EVENTS
+	bool "Event generation support"
+	select IIO_DUMMY_EVGEN
+	help
+	  Add some dummy events to the simple dummy driver.
+
+	  The purpose of this is to generate 'fake' event interrupts thus
+	  allowing that driver's code to be as close as possible to that
+	  a normal driver talking to hardware.
+
+config IIO_SIMPLE_DUMMY_BUFFER
+	bool "Buffered capture support"
+	select IIO_BUFFER
+	select IIO_TRIGGER
+	select IIO_KFIFO_BUF
+	select IIO_TRIGGERED_BUFFER
+	help
+	  Add buffered data capture to the simple dummy driver.
+
+	  Buffer handling elements of industrial I/O reference driver.
+	  Uses the kfifo buffer.
+
+endif # IIO_SIMPLE_DUMMY
+
+endmenu