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, 36 insertions, 0 deletions

diff --git a/drivers/accessibility/Kconfig b/drivers/accessibility/Kconfig
new file mode 100644
index 000000000..6b2f79d1f
--- /dev/null
+++ b/drivers/accessibility/Kconfig
@@ -0,0 +1,36 @@
+# SPDX-License-Identifier: GPL-2.0
+menuconfig ACCESSIBILITY
+	bool "Accessibility support"
+	help
+	  Accessibility handles all special kinds of hardware devices or
+	  software adapters which help people with disabilities (e.g.
+	  blindness) to use computers.
+
+	  That includes braille devices, speech synthesis, keyboard
+	  remapping, etc.
+
+	  Say Y here to get to see options for accessibility.
+	  This option alone does not add any kernel code.
+
+	  If you say N, all options in this submenu will be skipped and disabled.
+
+	  If unsure, say N.
+
+if ACCESSIBILITY
+config A11Y_BRAILLE_CONSOLE
+	bool "Console on braille device"
+	depends on VT
+	depends on SERIAL_CORE_CONSOLE
+	help
+	  Enables console output on a braille device connected to a 8250
+	  serial port. For now only the VisioBraille device is supported.
+
+	  To actually enable it, you need to pass option
+	  console=brl,ttyS0
+	  to the kernel. Options are the same as for serial console.
+
+	  If unsure, say N.
+
+source "drivers/accessibility/speakup/Kconfig"
+
+endif # ACCESSIBILITY