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, 29 insertions, 0 deletions

diff --git a/drivers/media/dvb-frontends/mxl692.h b/drivers/media/dvb-frontends/mxl692.h
new file mode 100644
index 000000000..77764a047
--- /dev/null
+++ b/drivers/media/dvb-frontends/mxl692.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Driver for the MaxLinear MxL69x family of tuners/demods
+ *
+ * Copyright (C) 2020 Brad Love <brad@nextdimension.cc>
+ *
+ * based on code:
+ * Copyright (c) 2016 MaxLinear, Inc. All rights reserved
+ * which was released under GPL V2
+ */
+
+#ifndef _MXL692_H_
+#define _MXL692_H_
+
+#include <media/dvb_frontend.h>
+
+#define MXL692_FIRMWARE "dvb-demod-mxl692.fw"
+
+struct mxl692_config {
+	unsigned char  id;
+	u8 i2c_addr;
+	/*
+	 * frontend
+	 * returned by driver
+	 */
+	struct dvb_frontend **fe;
+};
+
+#endif /* _MXL692_H_ */