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, 55 insertions, 0 deletions

diff --git a/drivers/media/dvb-frontends/drxd.h b/drivers/media/dvb-frontends/drxd.h
new file mode 100644
index 000000000..ba54fd9ad
--- /dev/null
+++ b/drivers/media/dvb-frontends/drxd.h
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * drxd.h: DRXD DVB-T demodulator driver
+ *
+ * Copyright (C) 2005-2007 Micronas
+ */
+
+#ifndef _DRXD_H_
+#define _DRXD_H_
+
+#include <linux/types.h>
+#include <linux/i2c.h>
+
+struct drxd_config {
+	u8 index;
+
+	u8 pll_address;
+	u8 pll_type;
+#define DRXD_PLL_NONE     0
+#define DRXD_PLL_DTT7520X 1
+#define DRXD_PLL_MT3X0823 2
+
+	u32 clock;
+	u8 insert_rs_byte;
+
+	u8 demod_address;
+	u8 demoda_address;
+	u8 demod_revision;
+
+	/* If the tuner is not behind an i2c gate, be sure to flip this bit
+	   or else the i2c bus could get wedged */
+	u8 disable_i2c_gate_ctrl;
+
+	u32 IF;
+	 s16(*osc_deviation) (void *priv, s16 dev, int flag);
+};
+
+#if IS_REACHABLE(CONFIG_DVB_DRXD)
+extern
+struct dvb_frontend *drxd_attach(const struct drxd_config *config,
+				 void *priv, struct i2c_adapter *i2c,
+				 struct device *dev);
+#else
+static inline
+struct dvb_frontend *drxd_attach(const struct drxd_config *config,
+				 void *priv, struct i2c_adapter *i2c,
+				 struct device *dev)
+{
+	printk(KERN_INFO "%s: not probed - driver disabled by Kconfig\n",
+	       __func__);
+	return NULL;
+}
+#endif
+
+#endif