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, 25 insertions, 0 deletions

diff --git a/tools/testing/cxl/watermark.h b/tools/testing/cxl/watermark.h
new file mode 100644
index 000000000..9d81d4a5f
--- /dev/null
+++ b/tools/testing/cxl/watermark.h
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2022 Intel Corporation. All rights reserved. */
+#ifndef _TEST_CXL_WATERMARK_H_
+#define _TEST_CXL_WATERMARK_H_
+#include <linux/module.h>
+#include <linux/printk.h>
+
+int cxl_acpi_test(void);
+int cxl_core_test(void);
+int cxl_mem_test(void);
+int cxl_pmem_test(void);
+int cxl_port_test(void);
+
+/*
+ * dummy routine for cxl_test to validate it is linking to the properly
+ * mocked module and not the standard one from the base tree.
+ */
+#define cxl_test_watermark(x)				\
+int x##_test(void)					\
+{							\
+	pr_debug("%s for cxl_test\n", KBUILD_MODNAME);	\
+	return 0;					\
+}							\
+EXPORT_SYMBOL(x##_test)
+#endif /* _TEST_CXL_WATERMARK_H_ */