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, 59 insertions, 0 deletions

diff --git a/drivers/clk/qcom/reset.c b/drivers/clk/qcom/reset.c
new file mode 100644
index 000000000..d96c96a90
--- /dev/null
+++ b/drivers/clk/qcom/reset.c
@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2013, The Linux Foundation. All rights reserved.
+ */
+
+#include <linux/bitops.h>
+#include <linux/export.h>
+#include <linux/regmap.h>
+#include <linux/reset-controller.h>
+#include <linux/delay.h>
+
+#include "reset.h"
+
+static int qcom_reset(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	struct qcom_reset_controller *rst = to_qcom_reset_controller(rcdev);
+
+	rcdev->ops->assert(rcdev, id);
+	fsleep(rst->reset_map[id].udelay ?: 1); /* use 1 us as default */
+
+	rcdev->ops->deassert(rcdev, id);
+	return 0;
+}
+
+static int qcom_reset_set_assert(struct reset_controller_dev *rcdev,
+				 unsigned long id, bool assert)
+{
+	struct qcom_reset_controller *rst;
+	const struct qcom_reset_map *map;
+	u32 mask;
+
+	rst = to_qcom_reset_controller(rcdev);
+	map = &rst->reset_map[id];
+	mask = map->bitmask ? map->bitmask : BIT(map->bit);
+
+	regmap_update_bits(rst->regmap, map->reg, mask, assert ? mask : 0);
+
+	/* Read back the register to ensure write completion, ignore the value */
+	regmap_read(rst->regmap, map->reg, &mask);
+
+	return 0;
+}
+
+static int qcom_reset_assert(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	return qcom_reset_set_assert(rcdev, id, true);
+}
+
+static int qcom_reset_deassert(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	return qcom_reset_set_assert(rcdev, id, false);
+}
+
+const struct reset_control_ops qcom_reset_ops = {
+	.reset = qcom_reset,
+	.assert = qcom_reset_assert,
+	.deassert = qcom_reset_deassert,
+};
+EXPORT_SYMBOL_GPL(qcom_reset_ops);