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, 52 insertions, 0 deletions

diff --git a/Documentation/fb/lxfb.rst b/Documentation/fb/lxfb.rst
new file mode 100644
index 000000000..0a176ab37
--- /dev/null
+++ b/Documentation/fb/lxfb.rst
@@ -0,0 +1,52 @@
+======================================
+lxfb - AMD Geode LX framebuffer driver
+======================================
+
+This is a graphics framebuffer driver for AMD Geode LX based processors.
+
+Advantages:
+
+ * No need to use AMD's VSA code (or other VESA emulation layer) in the
+   BIOS.
+ * It provides a nice large console (128 cols + 48 lines with 1024x768)
+   without using tiny, unreadable fonts.
+ * You can run XF68_FBDev on top of /dev/fb0
+ * Most important: boot logo :-)
+
+Disadvantages:
+
+ * graphic mode is slower than text mode...
+
+
+How to use it?
+==============
+
+Switching modes is done using  lxfb.mode_option=<resolution>... boot
+parameter or using `fbset` program.
+
+See Documentation/fb/modedb.rst for more information on modedb
+resolutions.
+
+
+X11
+===
+
+XF68_FBDev should generally work fine, but it is non-accelerated.
+
+
+Configuration
+=============
+
+You can pass kernel command line options to lxfb with lxfb.<option>.
+For example, lxfb.mode_option=800x600@75.
+Accepted options:
+
+================ ==================================================
+mode_option	 specify the video mode.  Of the form
+		 <x>x<y>[-<bpp>][@<refresh>]
+vram		 size of video ram (normally auto-detected)
+vt_switch	 enable vt switching during suspend/resume.  The vt
+		 switch is slow, but harmless.
+================ ==================================================
+
+Andres Salomon <dilinger@debian.org>