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, 82 insertions, 0 deletions

diff --git a/drivers/md/dm-io-tracker.h b/drivers/md/dm-io-tracker.h
new file mode 100644
index 000000000..bea1ca118
--- /dev/null
+++ b/drivers/md/dm-io-tracker.h
@@ -0,0 +1,82 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 Red Hat, Inc. All rights reserved.
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef DM_IO_TRACKER_H
+#define DM_IO_TRACKER_H
+
+#include <linux/jiffies.h>
+
+struct dm_io_tracker {
+	spinlock_t lock;
+
+	/*
+	 * Sectors of in-flight IO.
+	 */
+	sector_t in_flight;
+
+	/*
+	 * The time, in jiffies, when this device became idle
+	 * (if it is indeed idle).
+	 */
+	unsigned long idle_time;
+	unsigned long last_update_time;
+};
+
+static inline void dm_iot_init(struct dm_io_tracker *iot)
+{
+	spin_lock_init(&iot->lock);
+	iot->in_flight = 0ul;
+	iot->idle_time = 0ul;
+	iot->last_update_time = jiffies;
+}
+
+static inline bool dm_iot_idle_for(struct dm_io_tracker *iot, unsigned long j)
+{
+	bool r = false;
+
+	spin_lock_irq(&iot->lock);
+	if (!iot->in_flight)
+		r = time_after(jiffies, iot->idle_time + j);
+	spin_unlock_irq(&iot->lock);
+
+	return r;
+}
+
+static inline unsigned long dm_iot_idle_time(struct dm_io_tracker *iot)
+{
+	unsigned long r = 0;
+
+	spin_lock_irq(&iot->lock);
+	if (!iot->in_flight)
+		r = jiffies - iot->idle_time;
+	spin_unlock_irq(&iot->lock);
+
+	return r;
+}
+
+static inline void dm_iot_io_begin(struct dm_io_tracker *iot, sector_t len)
+{
+	spin_lock_irq(&iot->lock);
+	iot->in_flight += len;
+	spin_unlock_irq(&iot->lock);
+}
+
+static inline void dm_iot_io_end(struct dm_io_tracker *iot, sector_t len)
+{
+	unsigned long flags;
+
+	if (!len)
+		return;
+
+	spin_lock_irqsave(&iot->lock, flags);
+	iot->in_flight -= len;
+	if (!iot->in_flight)
+		iot->idle_time = jiffies;
+	spin_unlock_irqrestore(&iot->lock, flags);
+}
+
+#endif