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, 29 insertions, 0 deletions

diff --git a/drivers/mfd/cs42l43.h b/drivers/mfd/cs42l43.h
new file mode 100644
index 000000000..a0068f657
--- /dev/null
+++ b/drivers/mfd/cs42l43.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * CS42L43 core driver internal data
+ *
+ * Copyright (C) 2022-2023 Cirrus Logic, Inc. and
+ *                         Cirrus Logic International Semiconductor Ltd.
+ */
+
+#ifndef CS42L43_CORE_INT_H
+#define CS42L43_CORE_INT_H
+
+#define CS42L43_N_DEFAULTS 189
+
+struct dev_pm_ops;
+struct device;
+struct reg_default;
+
+struct cs42l43;
+
+extern const struct dev_pm_ops cs42l43_pm_ops;
+extern const struct reg_default cs42l43_reg_default[CS42L43_N_DEFAULTS];
+
+bool cs42l43_readable_register(struct device *dev, unsigned int reg);
+bool cs42l43_precious_register(struct device *dev, unsigned int reg);
+bool cs42l43_volatile_register(struct device *dev, unsigned int reg);
+
+int cs42l43_dev_probe(struct cs42l43 *cs42l43);
+
+#endif /* CS42L43_CORE_INT_H */