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, 44 insertions, 0 deletions

diff --git a/drivers/md/dm-vdo/flush.h b/drivers/md/dm-vdo/flush.h
new file mode 100644
index 000000000..97252d665
--- /dev/null
+++ b/drivers/md/dm-vdo/flush.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2023 Red Hat
+ */
+
+#ifndef VDO_FLUSH_H
+#define VDO_FLUSH_H
+
+#include "funnel-workqueue.h"
+#include "types.h"
+#include "vio.h"
+#include "wait-queue.h"
+
+/* A marker for tracking which journal entries are affected by a flush request. */
+struct vdo_flush {
+	/* The completion for enqueueing this flush request. */
+	struct vdo_completion completion;
+	/* The flush bios covered by this request */
+	struct bio_list bios;
+	/* The wait queue entry for this flush */
+	struct vdo_waiter waiter;
+	/* Which flush this struct represents */
+	sequence_number_t flush_generation;
+};
+
+struct flusher;
+
+int __must_check vdo_make_flusher(struct vdo *vdo);
+
+void vdo_free_flusher(struct flusher *flusher);
+
+thread_id_t __must_check vdo_get_flusher_thread_id(struct flusher *flusher);
+
+void vdo_complete_flushes(struct flusher *flusher);
+
+void vdo_dump_flusher(const struct flusher *flusher);
+
+void vdo_launch_flush(struct vdo *vdo, struct bio *bio);
+
+void vdo_drain_flusher(struct flusher *flusher, struct vdo_completion *completion);
+
+void vdo_resume_flusher(struct flusher *flusher, struct vdo_completion *parent);
+
+#endif /* VDO_FLUSH_H */