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, 85 insertions, 0 deletions

diff --git a/drivers/clk/sprd/div.h b/drivers/clk/sprd/div.h
new file mode 100644
index 000000000..a0bcad804
--- /dev/null
+++ b/drivers/clk/sprd/div.h
@@ -0,0 +1,85 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+//
+// Spreadtrum divider clock driver
+//
+// Copyright (C) 2017 Spreadtrum, Inc.
+// Author: Chunyan Zhang <chunyan.zhang@spreadtrum.com>
+
+#ifndef _SPRD_DIV_H_
+#define _SPRD_DIV_H_
+
+#include "common.h"
+
+/**
+ * struct sprd_div_internal - Internal divider description
+ * @shift: Bit offset of the divider in its register
+ * @width: Width of the divider field in its register
+ *
+ * That structure represents a single divider, and is meant to be
+ * embedded in other structures representing the various clock
+ * classes.
+ */
+struct sprd_div_internal {
+	s32	offset;
+	u8	shift;
+	u8	width;
+};
+
+#define _SPRD_DIV_CLK(_offset, _shift, _width)	\
+	{				\
+		.offset = _offset,	\
+		.shift	= _shift,	\
+		.width	= _width,	\
+	}
+
+struct sprd_div {
+	struct sprd_div_internal	div;
+	struct sprd_clk_common	common;
+};
+
+#define SPRD_DIV_CLK_HW_INIT_FN(_struct, _name, _parent, _reg, _offset,	\
+				_shift, _width, _flags, _fn)		\
+	struct sprd_div _struct = {					\
+		.div	= _SPRD_DIV_CLK(_offset, _shift, _width),	\
+		.common	= {						\
+			.regmap		= NULL,				\
+			.reg		= _reg,				\
+			.hw.init	= _fn(_name, _parent,		\
+					      &sprd_div_ops, _flags),	\
+		}							\
+	}
+
+#define SPRD_DIV_CLK(_struct, _name, _parent, _reg,			\
+		     _shift, _width, _flags)				\
+	SPRD_DIV_CLK_HW_INIT_FN(_struct, _name, _parent, _reg, 0x0,	\
+				_shift, _width, _flags, CLK_HW_INIT)
+
+#define SPRD_DIV_CLK_FW_NAME(_struct, _name, _parent, _reg,		\
+			_shift, _width, _flags)				\
+	SPRD_DIV_CLK_HW_INIT_FN(_struct, _name, _parent, _reg, 0x0,	\
+				_shift, _width, _flags, CLK_HW_INIT_FW_NAME)
+
+#define SPRD_DIV_CLK_HW(_struct, _name, _parent, _reg,			\
+			_shift, _width, _flags)				\
+	SPRD_DIV_CLK_HW_INIT_FN(_struct, _name, _parent, _reg, 0x0,	\
+				_shift, _width, _flags, CLK_HW_INIT_HW)
+
+static inline struct sprd_div *hw_to_sprd_div(const struct clk_hw *hw)
+{
+	struct sprd_clk_common *common = hw_to_sprd_clk_common(hw);
+
+	return container_of(common, struct sprd_div, common);
+}
+
+unsigned long sprd_div_helper_recalc_rate(struct sprd_clk_common *common,
+					  const struct sprd_div_internal *div,
+					  unsigned long parent_rate);
+
+int sprd_div_helper_set_rate(const struct sprd_clk_common *common,
+			     const struct sprd_div_internal *div,
+			     unsigned long rate,
+			     unsigned long parent_rate);
+
+extern const struct clk_ops sprd_div_ops;
+
+#endif /* _SPRD_DIV_H_ */