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, 62 insertions, 0 deletions

diff --git a/sound/firewire/fireface/ff-proc.c b/sound/firewire/fireface/ff-proc.c
new file mode 100644
index 000000000..4aecc8dcb
--- /dev/null
+++ b/sound/firewire/fireface/ff-proc.c
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ff-proc.c - a part of driver for RME Fireface series
+ *
+ * Copyright (c) 2015-2017 Takashi Sakamoto
+ */
+
+#include "./ff.h"
+
+const char *snd_ff_proc_get_clk_label(enum snd_ff_clock_src src)
+{
+	static const char *const labels[] = {
+		"Internal",
+		"S/PDIF",
+		"ADAT1",
+		"ADAT2",
+		"Word",
+		"LTC",
+	};
+
+	if (src >= ARRAY_SIZE(labels))
+		return NULL;
+
+	return labels[src];
+}
+
+static void proc_dump_status(struct snd_info_entry *entry,
+			     struct snd_info_buffer *buffer)
+{
+	struct snd_ff *ff = entry->private_data;
+
+	ff->spec->protocol->dump_status(ff, buffer);
+}
+
+static void add_node(struct snd_ff *ff, struct snd_info_entry *root,
+		     const char *name,
+		     void (*op)(struct snd_info_entry *e,
+				struct snd_info_buffer *b))
+{
+	struct snd_info_entry *entry;
+
+	entry = snd_info_create_card_entry(ff->card, name, root);
+	if (entry)
+		snd_info_set_text_ops(entry, ff, op);
+}
+
+void snd_ff_proc_init(struct snd_ff *ff)
+{
+	struct snd_info_entry *root;
+
+	/*
+	 * All nodes are automatically removed at snd_card_disconnect(),
+	 * by following to link list.
+	 */
+	root = snd_info_create_card_entry(ff->card, "firewire",
+					  ff->card->proc_root);
+	if (root == NULL)
+		return;
+	root->mode = S_IFDIR | 0555;
+
+	add_node(ff, root, "status", proc_dump_status);
+}