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, 123 insertions, 0 deletions

diff --git a/drivers/cpuidle/governor.c b/drivers/cpuidle/governor.c
new file mode 100644
index 000000000..5d0e7f78c
--- /dev/null
+++ b/drivers/cpuidle/governor.c
@@ -0,0 +1,123 @@
+/*
+ * governor.c - governor support
+ *
+ * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
+ *               Shaohua Li <shaohua.li@intel.com>
+ *               Adam Belay <abelay@novell.com>
+ *
+ * This code is licenced under the GPL.
+ */
+
+#include <linux/cpu.h>
+#include <linux/cpuidle.h>
+#include <linux/mutex.h>
+#include <linux/module.h>
+#include <linux/pm_qos.h>
+
+#include "cpuidle.h"
+
+char param_governor[CPUIDLE_NAME_LEN];
+
+LIST_HEAD(cpuidle_governors);
+struct cpuidle_governor *cpuidle_curr_governor;
+struct cpuidle_governor *cpuidle_prev_governor;
+
+/**
+ * cpuidle_find_governor - finds a governor of the specified name
+ * @str: the name
+ *
+ * Must be called with cpuidle_lock acquired.
+ */
+struct cpuidle_governor *cpuidle_find_governor(const char *str)
+{
+	struct cpuidle_governor *gov;
+
+	list_for_each_entry(gov, &cpuidle_governors, governor_list)
+		if (!strncasecmp(str, gov->name, CPUIDLE_NAME_LEN))
+			return gov;
+
+	return NULL;
+}
+
+/**
+ * cpuidle_switch_governor - changes the governor
+ * @gov: the new target governor
+ * Must be called with cpuidle_lock acquired.
+ */
+int cpuidle_switch_governor(struct cpuidle_governor *gov)
+{
+	struct cpuidle_device *dev;
+
+	if (!gov)
+		return -EINVAL;
+
+	if (gov == cpuidle_curr_governor)
+		return 0;
+
+	cpuidle_uninstall_idle_handler();
+
+	if (cpuidle_curr_governor) {
+		list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
+			cpuidle_disable_device(dev);
+	}
+
+	cpuidle_curr_governor = gov;
+
+	list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
+		cpuidle_enable_device(dev);
+
+	cpuidle_install_idle_handler();
+	pr_info("cpuidle: using governor %s\n", gov->name);
+
+	return 0;
+}
+
+/**
+ * cpuidle_register_governor - registers a governor
+ * @gov: the governor
+ */
+int cpuidle_register_governor(struct cpuidle_governor *gov)
+{
+	int ret = -EEXIST;
+
+	if (!gov || !gov->select)
+		return -EINVAL;
+
+	if (cpuidle_disabled())
+		return -ENODEV;
+
+	mutex_lock(&cpuidle_lock);
+	if (cpuidle_find_governor(gov->name) == NULL) {
+		ret = 0;
+		list_add_tail(&gov->governor_list, &cpuidle_governors);
+		if (!cpuidle_curr_governor ||
+		    !strncasecmp(param_governor, gov->name, CPUIDLE_NAME_LEN) ||
+		    (cpuidle_curr_governor->rating < gov->rating &&
+		     strncasecmp(param_governor, cpuidle_curr_governor->name,
+				 CPUIDLE_NAME_LEN)))
+			cpuidle_switch_governor(gov);
+	}
+	mutex_unlock(&cpuidle_lock);
+
+	return ret;
+}
+
+/**
+ * cpuidle_governor_latency_req - Compute a latency constraint for CPU
+ * @cpu: Target CPU
+ */
+s64 cpuidle_governor_latency_req(unsigned int cpu)
+{
+	struct device *device = get_cpu_device(cpu);
+	int device_req = dev_pm_qos_raw_resume_latency(device);
+	int global_req = cpu_latency_qos_limit();
+	int global_wake_req = cpu_wakeup_latency_qos_limit();
+
+	if (global_req > global_wake_req)
+		global_req = global_wake_req;
+
+	if (device_req > global_req)
+		device_req = global_req;
+
+	return (s64)device_req * NSEC_PER_USEC;
+}