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, 88 insertions, 0 deletions

diff --git a/drivers/usb/serial/wishbone-serial.c b/drivers/usb/serial/wishbone-serial.c
new file mode 100644
index 000000000..4a1fed4cb
--- /dev/null
+++ b/drivers/usb/serial/wishbone-serial.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * USB Wishbone-Serial adapter driver
+ *
+ * Copyright (C) 2013 Wesley W. Terpstra <w.terpstra@gsi.de>
+ * Copyright (C) 2013 GSI Helmholtz Centre for Heavy Ion Research GmbH
+ */
+
+#include <linux/kernel.h>
+#include <linux/tty.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+
+#define GSI_VENDOR_OPENCLOSE 0xB0
+
+static const struct usb_device_id id_table[] = {
+	{ USB_DEVICE_AND_INTERFACE_INFO(0x1D50, 0x6062, 0xFF, 0xFF, 0xFF) },
+	{ },
+};
+MODULE_DEVICE_TABLE(usb, id_table);
+
+/*
+ * Etherbone must be told that a new stream has begun before data arrives.
+ * This is necessary to restart the negotiation of Wishbone bus parameters.
+ * Similarly, when the stream ends, Etherbone must be told so that the cycle
+ * line can be driven low in the case that userspace failed to do so.
+ */
+static int usb_gsi_openclose(struct usb_serial_port *port, int value)
+{
+	struct usb_device *dev = port->serial->dev;
+
+	return usb_control_msg(
+		dev,
+		usb_sndctrlpipe(dev, 0), /* Send to EP0OUT */
+		GSI_VENDOR_OPENCLOSE,
+		USB_DIR_OUT|USB_TYPE_VENDOR|USB_RECIP_INTERFACE,
+		value, /* wValue = device is open(1) or closed(0) */
+		port->serial->interface->cur_altsetting->desc.bInterfaceNumber,
+		NULL, 0,  /* There is no data stage */
+		5000); /* Timeout till operation fails */
+}
+
+static int wishbone_serial_open(struct tty_struct *tty,
+				struct usb_serial_port *port)
+{
+	int retval;
+
+	retval = usb_gsi_openclose(port, 1);
+	if (retval) {
+		dev_err(&port->serial->dev->dev,
+		       "Could not mark device as open (%d)\n",
+		       retval);
+		return retval;
+	}
+
+	retval = usb_serial_generic_open(tty, port);
+	if (retval)
+		usb_gsi_openclose(port, 0);
+
+	return retval;
+}
+
+static void wishbone_serial_close(struct usb_serial_port *port)
+{
+	usb_serial_generic_close(port);
+	usb_gsi_openclose(port, 0);
+}
+
+static struct usb_serial_driver wishbone_serial_device = {
+	.driver = {
+		.name =		"wishbone_serial",
+	},
+	.id_table =		id_table,
+	.num_ports =		1,
+	.open =			&wishbone_serial_open,
+	.close =		&wishbone_serial_close,
+};
+
+static struct usb_serial_driver * const serial_drivers[] = {
+	&wishbone_serial_device, NULL
+};
+
+module_usb_serial_driver(serial_drivers, id_table);
+
+MODULE_AUTHOR("Wesley W. Terpstra <w.terpstra@gsi.de>");
+MODULE_DESCRIPTION("USB Wishbone-Serial adapter");
+MODULE_LICENSE("GPL");