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, 47 insertions, 0 deletions

diff --git a/drivers/gnss/serial.h b/drivers/gnss/serial.h
new file mode 100644
index 000000000..621953f78
--- /dev/null
+++ b/drivers/gnss/serial.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Generic serial GNSS receiver driver
+ *
+ * Copyright (C) 2018 Johan Hovold <johan@kernel.org>
+ */
+
+#ifndef _LINUX_GNSS_SERIAL_H
+#define _LINUX_GNSS_SERIAL_H
+
+#include <asm/termbits.h>
+#include <linux/pm.h>
+
+struct gnss_serial {
+	struct serdev_device *serdev;
+	struct gnss_device *gdev;
+	speed_t	speed;
+	const struct gnss_serial_ops *ops;
+	unsigned long drvdata[];
+};
+
+enum gnss_serial_pm_state {
+	GNSS_SERIAL_OFF,
+	GNSS_SERIAL_ACTIVE,
+	GNSS_SERIAL_STANDBY,
+};
+
+struct gnss_serial_ops {
+	int (*set_power)(struct gnss_serial *gserial,
+				enum gnss_serial_pm_state state);
+};
+
+extern const struct dev_pm_ops gnss_serial_pm_ops;
+
+struct gnss_serial *gnss_serial_allocate(struct serdev_device *gserial,
+						size_t data_size);
+void gnss_serial_free(struct gnss_serial *gserial);
+
+int gnss_serial_register(struct gnss_serial *gserial);
+void gnss_serial_deregister(struct gnss_serial *gserial);
+
+static inline void *gnss_serial_get_drvdata(struct gnss_serial *gserial)
+{
+	return gserial->drvdata;
+}
+
+#endif /* _LINUX_GNSS_SERIAL_H */