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, 45 insertions, 0 deletions

diff --git a/drivers/ptp/ptp_fc3.h b/drivers/ptp/ptp_fc3.h
new file mode 100644
index 000000000..897101579
--- /dev/null
+++ b/drivers/ptp/ptp_fc3.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * PTP hardware clock driver for the FemtoClock3 family of timing and
+ * synchronization devices.
+ *
+ * Copyright (C) 2023 Integrated Device Technology, Inc., a Renesas Company.
+ */
+#ifndef PTP_IDTFC3_H
+#define PTP_IDTFC3_H
+
+#include <linux/ktime.h>
+#include <linux/ptp_clock.h>
+#include <linux/regmap.h>
+
+#define FW_FILENAME	"idtfc3.bin"
+
+#define MAX_FFO_PPB	(244000)
+#define TDC_GET_PERIOD	(10)
+
+struct idtfc3 {
+	struct ptp_clock_info	caps;
+	struct ptp_clock	*ptp_clock;
+	struct device		*dev;
+	/* Mutex to protect operations from being interrupted */
+	struct mutex		*lock;
+	struct device		*mfd;
+	struct regmap		*regmap;
+	struct idtfc3_hw_param	hw_param;
+	u32			sub_sync_count;
+	u32			ns_per_sync;
+	int			tdc_offset_sign;
+	u64			tdc_apll_freq;
+	u32			time_ref_freq;
+	u16			fod_n;
+	u8			lpf_mode;
+	/* Time counter */
+	u32			last_counter;
+	s64			ns;
+	u32			ns_per_counter;
+	u32			tc_update_period;
+	u32			tc_write_timeout;
+	s64			tod_write_overhead;
+};
+
+#endif /* PTP_IDTFC3_H */