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, 71 insertions, 0 deletions

diff --git a/Documentation/fb/tgafb.rst b/Documentation/fb/tgafb.rst
new file mode 100644
index 000000000..f0944da1e
--- /dev/null
+++ b/Documentation/fb/tgafb.rst
@@ -0,0 +1,71 @@
+=======================================
+tgafb - TGA graphics framebuffer driver
+=======================================
+
+This is a driver for DECChip 21030 based graphics framebuffers, a.k.a. TGA
+cards, which are usually found in older Digital Alpha systems. The
+following models are supported:
+
+- ZLxP-E1 (8bpp, 2 MB VRAM)
+- ZLxP-E2 (32bpp, 8 MB VRAM)
+- ZLxP-E3 (32bpp, 16 MB VRAM, Zbuffer)
+
+This version is an almost complete rewrite of the code written by Geert
+Uytterhoeven, which was based on the original TGA console code written by
+Jay Estabrook.
+
+Major new features since Linux 2.0.x:
+
+ * Support for multiple resolutions
+ * Support for fixed-frequency and other oddball monitors
+   (by allowing the video mode to be set at boot time)
+
+User-visible changes since Linux 2.2.x:
+
+ * Sync-on-green is now handled properly
+ * More useful information is printed on bootup
+   (this helps if people run into problems)
+
+This driver does not (yet) support the TGA2 family of framebuffers, so the
+PowerStorm 3D30/4D20 (also known as PBXGB) cards are not supported. These
+can however be used with the standard VGA Text Console driver.
+
+
+Configuration
+=============
+
+You can pass kernel command line options to tgafb with
+`video=tgafb:option1,option2:value2,option3` (multiple options should be
+separated by comma, values are separated from options by `:`).
+
+Accepted options:
+
+==========  ============================================================
+font:X      default font to use. All fonts are supported, including the
+	    SUN12x22 font which is very nice at high resolutions.
+
+mode:X      default video mode. The following video modes are supported:
+	    640x480-60, 800x600-56, 640x480-72, 800x600-60, 800x600-72,
+	    1024x768-60, 1152x864-60, 1024x768-70, 1024x768-76,
+	    1152x864-70, 1280x1024-61, 1024x768-85, 1280x1024-70,
+	    1152x864-84, 1280x1024-76, 1280x1024-85
+==========  ============================================================
+
+
+Known Issues
+============
+
+The XFree86 FBDev server has been reported not to work, since tgafb doesn't do
+mmap(). Running the standard XF86_TGA server from XFree86 3.3.x works fine for
+me, however this server does not do acceleration, which make certain operations
+quite slow. Support for acceleration is being progressively integrated in
+XFree86 4.x.
+
+When running tgafb in resolutions higher than 640x480, on switching VCs from
+tgafb to XF86_TGA 3.3.x, the entire screen is not re-drawn and must be manually
+refreshed. This is an X server problem, not a tgafb problem, and is fixed in
+XFree86 4.0.
+
+Enjoy!
+
+Martin Lucina <mato@kotelna.sk>