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, 79 insertions, 0 deletions

diff --git a/drivers/scsi/arm/msgqueue.h b/drivers/scsi/arm/msgqueue.h
new file mode 100644
index 000000000..4bcc400f5
--- /dev/null
+++ b/drivers/scsi/arm/msgqueue.h
@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ *  linux/drivers/acorn/scsi/msgqueue.h
+ *
+ *  Copyright (C) 1997 Russell King
+ *
+ *  message queue handling
+ */
+#ifndef MSGQUEUE_H
+#define MSGQUEUE_H
+
+struct message {
+    char msg[8];
+    int length;
+    int fifo;
+};
+
+struct msgqueue_entry {
+    struct message msg;
+    struct msgqueue_entry *next;
+};
+
+#define NR_MESSAGES 4
+
+typedef struct {
+    struct msgqueue_entry *qe;
+    struct msgqueue_entry *free;
+    struct msgqueue_entry entries[NR_MESSAGES];
+} MsgQueue_t;
+
+/*
+ * Function: void msgqueue_initialise(MsgQueue_t *msgq)
+ * Purpose : initialise a message queue
+ * Params  : msgq - queue to initialise
+ */
+extern void msgqueue_initialise(MsgQueue_t *msgq);
+
+/*
+ * Function: void msgqueue_free(MsgQueue_t *msgq)
+ * Purpose : free a queue
+ * Params  : msgq - queue to free
+ */
+extern void msgqueue_free(MsgQueue_t *msgq);
+
+/*
+ * Function: int msgqueue_msglength(MsgQueue_t *msgq)
+ * Purpose : calculate the total length of all messages on the message queue
+ * Params  : msgq - queue to examine
+ * Returns : number of bytes of messages in queue
+ */
+extern int msgqueue_msglength(MsgQueue_t *msgq);
+
+/*
+ * Function: struct message *msgqueue_getmsg(MsgQueue_t *msgq, int msgno)
+ * Purpose : return a message & its length
+ * Params  : msgq   - queue to obtain message from
+ *         : msgno  - message number
+ * Returns : pointer to message string, or NULL
+ */
+extern struct message *msgqueue_getmsg(MsgQueue_t *msgq, int msgno);
+
+/*
+ * Function: int msgqueue_addmsg(MsgQueue_t *msgq, int length, ...)
+ * Purpose : add a message onto a message queue
+ * Params  : msgq   - queue to add message on
+ *	     length - length of message
+ *	     ...    - message bytes
+ * Returns : != 0 if successful
+ */
+extern int msgqueue_addmsg(MsgQueue_t *msgq, int length, ...);
+
+/*
+ * Function: void msgqueue_flush(MsgQueue_t *msgq)
+ * Purpose : flush all messages from message queue
+ * Params  : msgq - queue to flush
+ */
+extern void msgqueue_flush(MsgQueue_t *msgq);
+
+#endif