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, 209 insertions, 0 deletions

diff --git a/drivers/clk/tegra/clk-device.c b/drivers/clk/tegra/clk-device.c
new file mode 100644
index 000000000..a75f71462
--- /dev/null
+++ b/drivers/clk/tegra/clk-device.c
@@ -0,0 +1,209 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/pm_domain.h>
+#include <linux/pm_opp.h>
+#include <linux/pm_runtime.h>
+#include <linux/slab.h>
+
+#include <soc/tegra/common.h>
+
+#include "clk.h"
+
+/*
+ * This driver manages performance state of the core power domain for the
+ * independent PLLs and system clocks.  We created a virtual clock device
+ * for such clocks, see tegra_clk_dev_register().
+ */
+
+struct tegra_clk_device {
+	struct notifier_block clk_nb;
+	struct device *dev;
+	struct clk_hw *hw;
+	struct mutex lock;
+};
+
+static int tegra_clock_set_pd_state(struct tegra_clk_device *clk_dev,
+				    unsigned long rate)
+{
+	struct device *dev = clk_dev->dev;
+	struct dev_pm_opp *opp;
+	unsigned int pstate;
+
+	opp = dev_pm_opp_find_freq_ceil(dev, &rate);
+	if (opp == ERR_PTR(-ERANGE)) {
+		/*
+		 * Some clocks may be unused by a particular board and they
+		 * may have uninitiated clock rate that is overly high.  In
+		 * this case clock is expected to be disabled, but still we
+		 * need to set up performance state of the power domain and
+		 * not error out clk initialization.  A typical example is
+		 * a PCIe clock on Android tablets.
+		 */
+		dev_dbg(dev, "failed to find ceil OPP for %luHz\n", rate);
+		opp = dev_pm_opp_find_freq_floor(dev, &rate);
+	}
+
+	if (IS_ERR(opp)) {
+		dev_err(dev, "failed to find OPP for %luHz: %pe\n", rate, opp);
+		return PTR_ERR(opp);
+	}
+
+	pstate = dev_pm_opp_get_required_pstate(opp, 0);
+	dev_pm_opp_put(opp);
+
+	return dev_pm_genpd_set_performance_state(dev, pstate);
+}
+
+static int tegra_clock_change_notify(struct notifier_block *nb,
+				     unsigned long msg, void *data)
+{
+	struct clk_notifier_data *cnd = data;
+	struct tegra_clk_device *clk_dev;
+	int err = 0;
+
+	clk_dev = container_of(nb, struct tegra_clk_device, clk_nb);
+
+	mutex_lock(&clk_dev->lock);
+	switch (msg) {
+	case PRE_RATE_CHANGE:
+		if (cnd->new_rate > cnd->old_rate)
+			err = tegra_clock_set_pd_state(clk_dev, cnd->new_rate);
+		break;
+
+	case ABORT_RATE_CHANGE:
+		err = tegra_clock_set_pd_state(clk_dev, cnd->old_rate);
+		break;
+
+	case POST_RATE_CHANGE:
+		if (cnd->new_rate < cnd->old_rate)
+			err = tegra_clock_set_pd_state(clk_dev, cnd->new_rate);
+		break;
+
+	default:
+		break;
+	}
+	mutex_unlock(&clk_dev->lock);
+
+	return notifier_from_errno(err);
+}
+
+static int tegra_clock_sync_pd_state(struct tegra_clk_device *clk_dev)
+{
+	unsigned long rate;
+	int ret;
+
+	mutex_lock(&clk_dev->lock);
+
+	rate = clk_hw_get_rate(clk_dev->hw);
+	ret = tegra_clock_set_pd_state(clk_dev, rate);
+
+	mutex_unlock(&clk_dev->lock);
+
+	return ret;
+}
+
+static int tegra_clock_probe(struct platform_device *pdev)
+{
+	struct tegra_core_opp_params opp_params = {};
+	struct tegra_clk_device *clk_dev;
+	struct device *dev = &pdev->dev;
+	struct clk *clk;
+	int err;
+
+	if (!dev->pm_domain)
+		return -EINVAL;
+
+	clk_dev = devm_kzalloc(dev, sizeof(*clk_dev), GFP_KERNEL);
+	if (!clk_dev)
+		return -ENOMEM;
+
+	clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	clk_dev->dev = dev;
+	clk_dev->hw = __clk_get_hw(clk);
+	clk_dev->clk_nb.notifier_call = tegra_clock_change_notify;
+	mutex_init(&clk_dev->lock);
+
+	platform_set_drvdata(pdev, clk_dev);
+
+	/*
+	 * Runtime PM was already enabled for this device by the parent clk
+	 * driver and power domain state should be synced under clk_dev lock,
+	 * hence we don't use the common OPP helper that initializes OPP
+	 * state. For some clocks common OPP helper may fail to find ceil
+	 * rate, it's handled by this driver.
+	 */
+	err = devm_tegra_core_dev_init_opp_table(dev, &opp_params);
+	if (err)
+		return err;
+
+	err = clk_notifier_register(clk, &clk_dev->clk_nb);
+	if (err) {
+		dev_err(dev, "failed to register clk notifier: %d\n", err);
+		return err;
+	}
+
+	/*
+	 * The driver is attaching to a potentially active/resumed clock, hence
+	 * we need to sync the power domain performance state in a accordance to
+	 * the clock rate if clock is resumed.
+	 */
+	err = tegra_clock_sync_pd_state(clk_dev);
+	if (err)
+		goto unreg_clk;
+
+	return 0;
+
+unreg_clk:
+	clk_notifier_unregister(clk, &clk_dev->clk_nb);
+
+	return err;
+}
+
+/*
+ * Tegra GENPD driver enables clocks during NOIRQ phase. It can't be done
+ * for clocks served by this driver because runtime PM is unavailable in
+ * NOIRQ phase. We will keep clocks resumed during suspend to mitigate this
+ * problem. In practice this makes no difference from a power management
+ * perspective since voltage is kept at a nominal level during suspend anyways.
+ */
+static inline int tegra_clock_suspend(struct device *dev)
+{
+	int ret;
+
+	ret = pm_runtime_resume(dev);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static const struct dev_pm_ops tegra_clock_pm = {
+	SET_SYSTEM_SLEEP_PM_OPS(tegra_clock_suspend, NULL)
+};
+
+static const struct of_device_id tegra_clock_match[] = {
+	{ .compatible = "nvidia,tegra20-sclk" },
+	{ .compatible = "nvidia,tegra30-sclk" },
+	{ .compatible = "nvidia,tegra30-pllc" },
+	{ .compatible = "nvidia,tegra30-plle" },
+	{ .compatible = "nvidia,tegra30-pllm" },
+	{ }
+};
+
+static struct platform_driver tegra_clock_driver = {
+	.driver = {
+		.name = "tegra-clock",
+		.of_match_table = tegra_clock_match,
+		.pm = &tegra_clock_pm,
+		.suppress_bind_attrs = true,
+	},
+	.probe = tegra_clock_probe,
+};
+builtin_platform_driver(tegra_clock_driver);