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, 52 insertions, 0 deletions

diff --git a/drivers/media/dvb-frontends/dib3000.h b/drivers/media/dvb-frontends/dib3000.h
new file mode 100644
index 000000000..3f129efa2
--- /dev/null
+++ b/drivers/media/dvb-frontends/dib3000.h
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * public header file of the frontend drivers for mobile DVB-T demodulators
+ * DiBcom 3000M-B and DiBcom 3000P/M-C (http://www.dibcom.fr/)
+ *
+ * Copyright (C) 2004-5 Patrick Boettcher (patrick.boettcher@posteo.de)
+ *
+ * based on GPL code from DibCom, which has
+ *
+ * Copyright (C) 2004 Amaury Demol for DiBcom
+ *
+ * Acknowledgements
+ *
+ *  Amaury Demol from DiBcom for providing specs and driver
+ *  sources, on which this driver (and the dvb-dibusb) are based.
+ *
+ * see Documentation/driver-api/media/drivers/dvb-usb.rst for more information
+ */
+
+#ifndef DIB3000_H
+#define DIB3000_H
+
+#include <linux/dvb/frontend.h>
+
+struct dib3000_config
+{
+	/* the demodulator's i2c address */
+	u8 demod_address;
+};
+
+struct dib_fe_xfer_ops
+{
+	/* pid and transfer handling is done in the demodulator */
+	int (*pid_parse)(struct dvb_frontend *fe, int onoff);
+	int (*fifo_ctrl)(struct dvb_frontend *fe, int onoff);
+	int (*pid_ctrl)(struct dvb_frontend *fe, int index, int pid, int onoff);
+	int (*tuner_pass_ctrl)(struct dvb_frontend *fe, int onoff, u8 pll_ctrl);
+};
+
+#if IS_REACHABLE(CONFIG_DVB_DIB3000MB)
+extern struct dvb_frontend* dib3000mb_attach(const struct dib3000_config* config,
+					     struct i2c_adapter* i2c, struct dib_fe_xfer_ops *xfer_ops);
+#else
+static inline struct dvb_frontend* dib3000mb_attach(const struct dib3000_config* config,
+					     struct i2c_adapter* i2c, struct dib_fe_xfer_ops *xfer_ops)
+{
+	printk(KERN_WARNING "%s: driver disabled by Kconfig\n", __func__);
+	return NULL;
+}
+#endif // CONFIG_DVB_DIB3000MB
+
+#endif // DIB3000_H