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, 57 insertions, 0 deletions

diff --git a/include/video/videomode.h b/include/video/videomode.h
new file mode 100644
index 000000000..7b20ee6ea
--- /dev/null
+++ b/include/video/videomode.h
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2012 Steffen Trumtrar <s.trumtrar@pengutronix.de>
+ *
+ * generic videomode description
+ */
+
+#ifndef __LINUX_VIDEOMODE_H
+#define __LINUX_VIDEOMODE_H
+
+#include <linux/types.h>
+#include <video/display_timing.h>
+
+/*
+ * Subsystem independent description of a videomode.
+ * Can be generated from struct display_timing.
+ */
+struct videomode {
+	unsigned long pixelclock;	/* pixelclock in Hz */
+
+	u32 hactive;
+	u32 hfront_porch;
+	u32 hback_porch;
+	u32 hsync_len;
+
+	u32 vactive;
+	u32 vfront_porch;
+	u32 vback_porch;
+	u32 vsync_len;
+
+	enum display_flags flags; /* display flags */
+};
+
+/**
+ * videomode_from_timing - convert display timing to videomode
+ * @dt: display_timing structure
+ * @vm: return value
+ *
+ * DESCRIPTION:
+ * This function converts a struct display_timing to a struct videomode.
+ */
+void videomode_from_timing(const struct display_timing *dt,
+			  struct videomode *vm);
+
+/**
+ * videomode_from_timings - convert one display timings entry to videomode
+ * @disp: structure with all possible timing entries
+ * @vm: return value
+ * @index: index into the list of display timings in devicetree
+ *
+ * DESCRIPTION:
+ * This function converts one struct display_timing entry to a struct videomode.
+ */
+int videomode_from_timings(const struct display_timings *disp,
+			  struct videomode *vm, unsigned int index);
+
+#endif