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/Documentation/fb/arkfb.rst b/Documentation/fb/arkfb.rst
new file mode 100644
index 000000000..aeca8773d
--- /dev/null
+++ b/Documentation/fb/arkfb.rst
@@ -0,0 +1,68 @@
+========================================
+arkfb - fbdev driver for ARK Logic chips
+========================================
+
+
+Supported Hardware
+==================
+
+	ARK 2000PV chip
+	ICS 5342 ramdac
+
+	- only BIOS initialized VGA devices supported
+	- probably not working on big endian
+
+
+Supported Features
+==================
+
+	*  4 bpp pseudocolor modes (with 18bit palette, two variants)
+	*  8 bpp pseudocolor mode (with 18bit palette)
+	* 16 bpp truecolor modes (RGB 555 and RGB 565)
+	* 24 bpp truecolor mode (RGB 888)
+	* 32 bpp truecolor mode (RGB 888)
+	* text mode (activated by bpp = 0)
+	* doublescan mode variant (not available in text mode)
+	* panning in both directions
+	* suspend/resume support
+
+Text mode is supported even in higher resolutions, but there is limitation to
+lower pixclocks (i got maximum about 70 MHz, it is dependent on specific
+hardware). This limitation is not enforced by driver. Text mode supports 8bit
+wide fonts only (hardware limitation) and 16bit tall fonts (driver
+limitation). Unfortunately character attributes (like color) in text mode are
+broken for unknown reason, so its usefulness is limited.
+
+There are two 4 bpp modes. First mode (selected if nonstd == 0) is mode with
+packed pixels, high nibble first. Second mode (selected if nonstd == 1) is mode
+with interleaved planes (1 byte interleave), MSB first. Both modes support
+8bit wide fonts only (driver limitation).
+
+Suspend/resume works on systems that initialize video card during resume and
+if device is active (for example used by fbcon).
+
+
+Missing Features
+================
+(alias TODO list)
+
+	* secondary (not initialized by BIOS) device support
+	* big endian support
+	* DPMS support
+	* MMIO support
+	* interlaced mode variant
+	* support for fontwidths != 8 in 4 bpp modes
+	* support for fontheight != 16 in text mode
+	* hardware cursor
+	* vsync synchronization
+	* feature connector support
+	* acceleration support (8514-like 2D)
+
+
+Known bugs
+==========
+
+	* character attributes (and cursor) in text mode are broken
+
+--
+Ondrej Zajicek <santiago@crfreenet.org>