1 files changed, 166 insertions, 0 deletions
diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h
new file mode 100644
index 000000000..ccdaa8fd5
--- /dev/null
+++ b/include/linux/stop_machine.h
@@ -0,0 +1,166 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_STOP_MACHINE
+#define _LINUX_STOP_MACHINE
+
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+#include <linux/smp.h>
+#include <linux/list.h>
+
+/*
+ * stop_cpu[s]() is simplistic per-cpu maximum priority cpu
+ * monopolization mechanism.  The caller can specify a non-sleeping
+ * function to be executed on a single or multiple cpus preempting all
+ * other processes and monopolizing those cpus until it finishes.
+ *
+ * Resources for this mechanism are preallocated when a cpu is brought
+ * up and requests are guaranteed to be served as long as the target
+ * cpus are online.
+ */
+typedef int (*cpu_stop_fn_t)(void *arg);
+
+#ifdef CONFIG_SMP
+
+struct cpu_stop_work {
+	struct list_head	list;		/* cpu_stopper->works */
+	cpu_stop_fn_t		fn;
+	void			*arg;
+	struct cpu_stop_done	*done;
+};
+
+int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
+int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);
+bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
+			 struct cpu_stop_work *work_buf);
+int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
+int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
+void stop_machine_park(int cpu);
+void stop_machine_unpark(int cpu);
+
+#else	/* CONFIG_SMP */
+
+#include <linux/workqueue.h>
+
+struct cpu_stop_work {
+	struct work_struct	work;
+	cpu_stop_fn_t		fn;
+	void			*arg;
+};
+
+static inline int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
+{
+	int ret = -ENOENT;
+	preempt_disable();
+	if (cpu == smp_processor_id())
+		ret = fn(arg);
+	preempt_enable();
+	return ret;
+}
+
+static void stop_one_cpu_nowait_workfn(struct work_struct *work)
+{
+	struct cpu_stop_work *stwork =
+		container_of(work, struct cpu_stop_work, work);
+	preempt_disable();
+	stwork->fn(stwork->arg);
+	preempt_enable();
+}
+
+static inline bool stop_one_cpu_nowait(unsigned int cpu,
+				       cpu_stop_fn_t fn, void *arg,
+				       struct cpu_stop_work *work_buf)
+{
+	if (cpu == smp_processor_id()) {
+		INIT_WORK(&work_buf->work, stop_one_cpu_nowait_workfn);
+		work_buf->fn = fn;
+		work_buf->arg = arg;
+		schedule_work(&work_buf->work);
+		return true;
+	}
+
+	return false;
+}
+
+static inline int stop_cpus(const struct cpumask *cpumask,
+			    cpu_stop_fn_t fn, void *arg)
+{
+	if (cpumask_test_cpu(raw_smp_processor_id(), cpumask))
+		return stop_one_cpu(raw_smp_processor_id(), fn, arg);
+	return -ENOENT;
+}
+
+static inline int try_stop_cpus(const struct cpumask *cpumask,
+				cpu_stop_fn_t fn, void *arg)
+{
+	return stop_cpus(cpumask, fn, arg);
+}
+
+#endif	/* CONFIG_SMP */
+
+/*
+ * stop_machine "Bogolock": stop the entire machine, disable
+ * interrupts.  This is a very heavy lock, which is equivalent to
+ * grabbing every spinlock (and more).  So the "read" side to such a
+ * lock is anything which disables preemption.
+ */
+#if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU)
+
+/**
+ * stop_machine: freeze the machine on all CPUs and run this function
+ * @fn: the function to run
+ * @data: the data ptr for the @fn()
+ * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
+ *
+ * Description: This causes a thread to be scheduled on every cpu,
+ * each of which disables interrupts.  The result is that no one is
+ * holding a spinlock or inside any other preempt-disabled region when
+ * @fn() runs.
+ *
+ * This can be thought of as a very heavy write lock, equivalent to
+ * grabbing every spinlock in the kernel.
+ *
+ * Protects against CPU hotplug.
+ */
+int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
+
+/**
+ * stop_machine_cpuslocked: freeze the machine on all CPUs and run this function
+ * @fn: the function to run
+ * @data: the data ptr for the @fn()
+ * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
+ *
+ * Same as above. Must be called from with in a cpus_read_lock() protected
+ * region. Avoids nested calls to cpus_read_lock().
+ */
+int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
+
+int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
+				   const struct cpumask *cpus);
+#else	/* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
+
+static __always_inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
+					  const struct cpumask *cpus)
+{
+	unsigned long flags;
+	int ret;
+	local_irq_save(flags);
+	ret = fn(data);
+	local_irq_restore(flags);
+	return ret;
+}
+
+static __always_inline int
+stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
+{
+	return stop_machine_cpuslocked(fn, data, cpus);
+}
+
+static __always_inline int
+stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
+			       const struct cpumask *cpus)
+{
+	return stop_machine(fn, data, cpus);
+}
+
+#endif	/* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
+#endif	/* _LINUX_STOP_MACHINE */