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, 52 insertions, 0 deletions

diff --git a/sound/firewire/cmp.h b/sound/firewire/cmp.h
new file mode 100644
index 000000000..66fc08b74
--- /dev/null
+++ b/sound/firewire/cmp.h
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef SOUND_FIREWIRE_CMP_H_INCLUDED
+#define SOUND_FIREWIRE_CMP_H_INCLUDED
+
+#include <linux/mutex.h>
+#include <linux/types.h>
+#include "iso-resources.h"
+
+struct fw_unit;
+
+enum cmp_direction {
+	CMP_INPUT = 0,
+	CMP_OUTPUT,
+};
+
+/**
+ * struct cmp_connection - manages an isochronous connection to a device
+ * @speed: the connection's actual speed
+ *
+ * This structure manages (using CMP) an isochronous stream between the local
+ * computer and a device's input plug (iPCR) and output plug (oPCR).
+ *
+ * There is no corresponding oPCR created on the local computer, so it is not
+ * possible to overlay connections on top of this one.
+ */
+struct cmp_connection {
+	int speed;
+	/* private: */
+	bool connected;
+	struct mutex mutex;
+	struct fw_iso_resources resources;
+	__be32 last_pcr_value;
+	unsigned int pcr_index;
+	unsigned int max_speed;
+	enum cmp_direction direction;
+};
+
+int cmp_connection_init(struct cmp_connection *connection,
+			struct fw_unit *unit,
+			enum cmp_direction direction,
+			unsigned int pcr_index);
+int cmp_connection_check_used(struct cmp_connection *connection, bool *used);
+void cmp_connection_destroy(struct cmp_connection *connection);
+
+int cmp_connection_reserve(struct cmp_connection *connection,
+			   unsigned int max_payload);
+void cmp_connection_release(struct cmp_connection *connection);
+
+int cmp_connection_establish(struct cmp_connection *connection);
+void cmp_connection_break(struct cmp_connection *connection);
+
+#endif