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, 68 insertions, 0 deletions

diff --git a/drivers/gnss/Kconfig b/drivers/gnss/Kconfig
new file mode 100644
index 000000000..d7fe265c2
--- /dev/null
+++ b/drivers/gnss/Kconfig
@@ -0,0 +1,68 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# GNSS receiver configuration
+#
+
+menuconfig GNSS
+	tristate "GNSS receiver support"
+	help
+	  Say Y here if you have a GNSS receiver (e.g. a GPS receiver).
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called gnss.
+
+if GNSS
+
+config GNSS_SERIAL
+	tristate
+
+config GNSS_MTK_SERIAL
+	tristate "Mediatek GNSS receiver support"
+	depends on SERIAL_DEV_BUS
+	select GNSS_SERIAL
+	help
+	  Say Y here if you have a Mediatek-based GNSS receiver which uses a
+	  serial interface.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called gnss-mtk.
+
+	  If unsure, say N.
+
+config GNSS_SIRF_SERIAL
+	tristate "SiRFstar GNSS receiver support"
+	depends on SERIAL_DEV_BUS
+	help
+	  Say Y here if you have a SiRFstar-based GNSS receiver which uses a
+	  serial interface.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called gnss-sirf.
+
+	  If unsure, say N.
+
+config GNSS_UBX_SERIAL
+	tristate "u-blox GNSS receiver support"
+	depends on SERIAL_DEV_BUS
+	select GNSS_SERIAL
+	help
+	  Say Y here if you have a u-blox GNSS receiver which uses a serial
+	  interface.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called gnss-ubx.
+
+	  If unsure, say N.
+
+config GNSS_USB
+	tristate "USB GNSS receiver support"
+	depends on USB
+	help
+	  Say Y here if you have a GNSS receiver which uses a USB interface.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called gnss-usb.
+
+	  If unsure, say N.
+
+endif # GNSS