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, 244 insertions, 0 deletions

diff --git a/drivers/thermal/thermal_thresholds.c b/drivers/thermal/thermal_thresholds.c
new file mode 100644
index 000000000..970b8fd33
--- /dev/null
+++ b/drivers/thermal/thermal_thresholds.c
@@ -0,0 +1,244 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2024 Linaro Limited
+ *
+ * Author: Daniel Lezcano <daniel.lezcano@linaro.org>
+ *
+ * Thermal thresholds
+ */
+#include <linux/list.h>
+#include <linux/list_sort.h>
+#include <linux/slab.h>
+
+#include "thermal_core.h"
+#include "thermal_thresholds.h"
+
+int thermal_thresholds_init(struct thermal_zone_device *tz)
+{
+	INIT_LIST_HEAD(&tz->user_thresholds);
+
+	return 0;
+}
+
+static void __thermal_thresholds_flush(struct thermal_zone_device *tz)
+{
+	struct list_head *thresholds = &tz->user_thresholds;
+	struct user_threshold *entry, *tmp;
+
+	list_for_each_entry_safe(entry, tmp, thresholds, list_node) {
+		list_del(&entry->list_node);
+		kfree(entry);
+	}
+}
+
+void thermal_thresholds_flush(struct thermal_zone_device *tz)
+{
+	lockdep_assert_held(&tz->lock);
+
+	__thermal_thresholds_flush(tz);
+
+	thermal_notify_threshold_flush(tz);
+
+	__thermal_zone_device_update(tz, THERMAL_TZ_FLUSH_THRESHOLDS);
+}
+
+void thermal_thresholds_exit(struct thermal_zone_device *tz)
+{
+	__thermal_thresholds_flush(tz);
+}
+
+static int __thermal_thresholds_cmp(void *data,
+				    const struct list_head *l1,
+				    const struct list_head *l2)
+{
+	struct user_threshold *t1 = container_of(l1, struct user_threshold, list_node);
+	struct user_threshold *t2 = container_of(l2, struct user_threshold, list_node);
+
+	return t1->temperature - t2->temperature;
+}
+
+static struct user_threshold *__thermal_thresholds_find(const struct list_head *thresholds,
+							int temperature)
+{
+	struct user_threshold *t;
+
+	list_for_each_entry(t, thresholds, list_node)
+		if (t->temperature == temperature)
+			return t;
+
+	return NULL;
+}
+
+static bool thermal_thresholds_handle_raising(struct list_head *thresholds, int temperature,
+					      int last_temperature)
+{
+	struct user_threshold *t;
+
+	list_for_each_entry(t, thresholds, list_node) {
+
+		if (!(t->direction & THERMAL_THRESHOLD_WAY_UP))
+		    continue;
+
+		if (temperature >= t->temperature &&
+		    last_temperature < t->temperature)
+			return true;
+	}
+
+	return false;
+}
+
+static bool thermal_thresholds_handle_dropping(struct list_head *thresholds, int temperature,
+					       int last_temperature)
+{
+	struct user_threshold *t;
+
+	list_for_each_entry_reverse(t, thresholds, list_node) {
+
+		if (!(t->direction & THERMAL_THRESHOLD_WAY_DOWN))
+		    continue;
+
+		if (temperature <= t->temperature &&
+		    last_temperature > t->temperature)
+			return true;
+	}
+
+	return false;
+}
+
+static void thermal_threshold_find_boundaries(struct list_head *thresholds, int temperature,
+					      int *low, int *high)
+{
+	struct user_threshold *t;
+
+	list_for_each_entry(t, thresholds, list_node) {
+		if (temperature < t->temperature &&
+		    (t->direction & THERMAL_THRESHOLD_WAY_UP) &&
+		    *high > t->temperature)
+			*high = t->temperature;
+	}
+
+	list_for_each_entry_reverse(t, thresholds, list_node) {
+		if (temperature > t->temperature &&
+		    (t->direction & THERMAL_THRESHOLD_WAY_DOWN) &&
+		    *low < t->temperature)
+			*low = t->temperature;
+	}
+}
+
+void thermal_thresholds_handle(struct thermal_zone_device *tz, int *low, int *high)
+{
+	struct list_head *thresholds = &tz->user_thresholds;
+
+	int temperature = tz->temperature;
+	int last_temperature = tz->last_temperature;
+
+	lockdep_assert_held(&tz->lock);
+
+	thermal_threshold_find_boundaries(thresholds, temperature, low, high);
+
+	/*
+	 * We need a second update in order to detect a threshold being crossed
+	 */
+	if (last_temperature == THERMAL_TEMP_INVALID)
+		return;
+
+	/*
+	 * The temperature is stable, so obviously we can not have
+	 * crossed a threshold.
+	 */
+	if (last_temperature == temperature)
+		return;
+
+	/*
+	 * Since last update the temperature:
+	 * - increased : thresholds are crossed the way up
+	 * - decreased : thresholds are crossed the way down
+	 */
+	if (temperature > last_temperature) {
+		if (thermal_thresholds_handle_raising(thresholds,
+						      temperature, last_temperature))
+			thermal_notify_threshold_up(tz);
+	} else {
+		if (thermal_thresholds_handle_dropping(thresholds,
+						       temperature, last_temperature))
+			thermal_notify_threshold_down(tz);
+	}
+}
+
+int thermal_thresholds_add(struct thermal_zone_device *tz,
+			   int temperature, int direction)
+{
+	struct list_head *thresholds = &tz->user_thresholds;
+	struct user_threshold *t;
+
+	lockdep_assert_held(&tz->lock);
+
+	t = __thermal_thresholds_find(thresholds, temperature);
+	if (t) {
+		if (t->direction == direction)
+			return -EEXIST;
+
+		t->direction |= direction;
+	} else {
+
+		t = kmalloc_obj(*t);
+		if (!t)
+			return -ENOMEM;
+
+		INIT_LIST_HEAD(&t->list_node);
+		t->temperature = temperature;
+		t->direction = direction;
+		list_add(&t->list_node, thresholds);
+		list_sort(NULL, thresholds, __thermal_thresholds_cmp);
+	}
+
+	thermal_notify_threshold_add(tz, temperature, direction);
+
+	__thermal_zone_device_update(tz, THERMAL_TZ_ADD_THRESHOLD);
+
+	return 0;
+}
+
+int thermal_thresholds_delete(struct thermal_zone_device *tz,
+			      int temperature, int direction)
+{
+	struct list_head *thresholds = &tz->user_thresholds;
+	struct user_threshold *t;
+
+	lockdep_assert_held(&tz->lock);
+
+	t = __thermal_thresholds_find(thresholds, temperature);
+	if (!t)
+		return -ENOENT;
+
+	if (t->direction == direction) {
+		list_del(&t->list_node);
+		kfree(t);
+	} else {
+		t->direction &= ~direction;
+	}
+
+	thermal_notify_threshold_delete(tz, temperature, direction);
+
+	__thermal_zone_device_update(tz, THERMAL_TZ_DEL_THRESHOLD);
+
+	return 0;
+}
+
+int thermal_thresholds_for_each(struct thermal_zone_device *tz,
+				int (*cb)(struct user_threshold *, void *arg), void *arg)
+{
+	struct list_head *thresholds = &tz->user_thresholds;
+	struct user_threshold *entry;
+	int ret;
+
+	guard(thermal_zone)(tz);
+
+	list_for_each_entry(entry, thresholds, list_node) {
+		ret = cb(entry, arg);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}