Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 682 insertions, 0 deletions

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
new file mode 100644
index 000000000..067cb83f3
--- /dev/null
+++ b/kernel/stop_machine.c
@@ -0,0 +1,682 @@
+/*
+ * kernel/stop_machine.c
+ *
+ * Copyright (C) 2008, 2005	IBM Corporation.
+ * Copyright (C) 2008, 2005	Rusty Russell rusty@rustcorp.com.au
+ * Copyright (C) 2010		SUSE Linux Products GmbH
+ * Copyright (C) 2010		Tejun Heo <tj@kernel.org>
+ *
+ * This file is released under the GPLv2 and any later version.
+ */
+#include <linux/completion.h>
+#include <linux/cpu.h>
+#include <linux/init.h>
+#include <linux/kthread.h>
+#include <linux/export.h>
+#include <linux/percpu.h>
+#include <linux/sched.h>
+#include <linux/stop_machine.h>
+#include <linux/interrupt.h>
+#include <linux/kallsyms.h>
+#include <linux/smpboot.h>
+#include <linux/atomic.h>
+#include <linux/nmi.h>
+#include <linux/sched/wake_q.h>
+
+/*
+ * Structure to determine completion condition and record errors.  May
+ * be shared by works on different cpus.
+ */
+struct cpu_stop_done {
+	atomic_t		nr_todo;	/* nr left to execute */
+	int			ret;		/* collected return value */
+	struct completion	completion;	/* fired if nr_todo reaches 0 */
+};
+
+/* the actual stopper, one per every possible cpu, enabled on online cpus */
+struct cpu_stopper {
+	struct task_struct	*thread;
+
+	raw_spinlock_t		lock;
+	bool			enabled;	/* is this stopper enabled? */
+	struct list_head	works;		/* list of pending works */
+
+	struct cpu_stop_work	stop_work;	/* for stop_cpus */
+};
+
+static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper);
+static bool stop_machine_initialized = false;
+
+/* static data for stop_cpus */
+static DEFINE_MUTEX(stop_cpus_mutex);
+static bool stop_cpus_in_progress;
+
+static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo)
+{
+	memset(done, 0, sizeof(*done));
+	atomic_set(&done->nr_todo, nr_todo);
+	init_completion(&done->completion);
+}
+
+/* signal completion unless @done is NULL */
+static void cpu_stop_signal_done(struct cpu_stop_done *done)
+{
+	if (atomic_dec_and_test(&done->nr_todo))
+		complete(&done->completion);
+}
+
+static void __cpu_stop_queue_work(struct cpu_stopper *stopper,
+					struct cpu_stop_work *work,
+					struct wake_q_head *wakeq)
+{
+	list_add_tail(&work->list, &stopper->works);
+	wake_q_add(wakeq, stopper->thread);
+}
+
+/* queue @work to @stopper.  if offline, @work is completed immediately */
+static bool cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work)
+{
+	struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
+	DEFINE_WAKE_Q(wakeq);
+	unsigned long flags;
+	bool enabled;
+
+	preempt_disable();
+	raw_spin_lock_irqsave(&stopper->lock, flags);
+	enabled = stopper->enabled;
+	if (enabled)
+		__cpu_stop_queue_work(stopper, work, &wakeq);
+	else if (work->done)
+		cpu_stop_signal_done(work->done);
+	raw_spin_unlock_irqrestore(&stopper->lock, flags);
+
+	wake_up_q(&wakeq);
+	preempt_enable();
+
+	return enabled;
+}
+
+/**
+ * stop_one_cpu - stop a cpu
+ * @cpu: cpu to stop
+ * @fn: function to execute
+ * @arg: argument to @fn
+ *
+ * Execute @fn(@arg) on @cpu.  @fn is run in a process context with
+ * the highest priority preempting any task on the cpu and
+ * monopolizing it.  This function returns after the execution is
+ * complete.
+ *
+ * This function doesn't guarantee @cpu stays online till @fn
+ * completes.  If @cpu goes down in the middle, execution may happen
+ * partially or fully on different cpus.  @fn should either be ready
+ * for that or the caller should ensure that @cpu stays online until
+ * this function completes.
+ *
+ * CONTEXT:
+ * Might sleep.
+ *
+ * RETURNS:
+ * -ENOENT if @fn(@arg) was not executed because @cpu was offline;
+ * otherwise, the return value of @fn.
+ */
+int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
+{
+	struct cpu_stop_done done;
+	struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done };
+
+	cpu_stop_init_done(&done, 1);
+	if (!cpu_stop_queue_work(cpu, &work))
+		return -ENOENT;
+	/*
+	 * In case @cpu == smp_proccessor_id() we can avoid a sleep+wakeup
+	 * cycle by doing a preemption:
+	 */
+	cond_resched();
+	wait_for_completion(&done.completion);
+	return done.ret;
+}
+
+/* This controls the threads on each CPU. */
+enum multi_stop_state {
+	/* Dummy starting state for thread. */
+	MULTI_STOP_NONE,
+	/* Awaiting everyone to be scheduled. */
+	MULTI_STOP_PREPARE,
+	/* Disable interrupts. */
+	MULTI_STOP_DISABLE_IRQ,
+	/* Run the function */
+	MULTI_STOP_RUN,
+	/* Exit */
+	MULTI_STOP_EXIT,
+};
+
+struct multi_stop_data {
+	cpu_stop_fn_t		fn;
+	void			*data;
+	/* Like num_online_cpus(), but hotplug cpu uses us, so we need this. */
+	unsigned int		num_threads;
+	const struct cpumask	*active_cpus;
+
+	enum multi_stop_state	state;
+	atomic_t		thread_ack;
+};
+
+static void set_state(struct multi_stop_data *msdata,
+		      enum multi_stop_state newstate)
+{
+	/* Reset ack counter. */
+	atomic_set(&msdata->thread_ack, msdata->num_threads);
+	smp_wmb();
+	msdata->state = newstate;
+}
+
+/* Last one to ack a state moves to the next state. */
+static void ack_state(struct multi_stop_data *msdata)
+{
+	if (atomic_dec_and_test(&msdata->thread_ack))
+		set_state(msdata, msdata->state + 1);
+}
+
+/* This is the cpu_stop function which stops the CPU. */
+static int multi_cpu_stop(void *data)
+{
+	struct multi_stop_data *msdata = data;
+	enum multi_stop_state curstate = MULTI_STOP_NONE;
+	int cpu = smp_processor_id(), err = 0;
+	unsigned long flags;
+	bool is_active;
+
+	/*
+	 * When called from stop_machine_from_inactive_cpu(), irq might
+	 * already be disabled.  Save the state and restore it on exit.
+	 */
+	local_save_flags(flags);
+
+	if (!msdata->active_cpus)
+		is_active = cpu == cpumask_first(cpu_online_mask);
+	else
+		is_active = cpumask_test_cpu(cpu, msdata->active_cpus);
+
+	/* Simple state machine */
+	do {
+		/* Chill out and ensure we re-read multi_stop_state. */
+		cpu_relax_yield();
+		if (msdata->state != curstate) {
+			curstate = msdata->state;
+			switch (curstate) {
+			case MULTI_STOP_DISABLE_IRQ:
+				local_irq_disable();
+				hard_irq_disable();
+				break;
+			case MULTI_STOP_RUN:
+				if (is_active)
+					err = msdata->fn(msdata->data);
+				break;
+			default:
+				break;
+			}
+			ack_state(msdata);
+		} else if (curstate > MULTI_STOP_PREPARE) {
+			/*
+			 * At this stage all other CPUs we depend on must spin
+			 * in the same loop. Any reason for hard-lockup should
+			 * be detected and reported on their side.
+			 */
+			touch_nmi_watchdog();
+		}
+	} while (curstate != MULTI_STOP_EXIT);
+
+	local_irq_restore(flags);
+	return err;
+}
+
+static int cpu_stop_queue_two_works(int cpu1, struct cpu_stop_work *work1,
+				    int cpu2, struct cpu_stop_work *work2)
+{
+	struct cpu_stopper *stopper1 = per_cpu_ptr(&cpu_stopper, cpu1);
+	struct cpu_stopper *stopper2 = per_cpu_ptr(&cpu_stopper, cpu2);
+	DEFINE_WAKE_Q(wakeq);
+	int err;
+
+retry:
+	/*
+	 * The waking up of stopper threads has to happen in the same
+	 * scheduling context as the queueing.  Otherwise, there is a
+	 * possibility of one of the above stoppers being woken up by another
+	 * CPU, and preempting us. This will cause us to not wake up the other
+	 * stopper forever.
+	 */
+	preempt_disable();
+	raw_spin_lock_irq(&stopper1->lock);
+	raw_spin_lock_nested(&stopper2->lock, SINGLE_DEPTH_NESTING);
+
+	if (!stopper1->enabled || !stopper2->enabled) {
+		err = -ENOENT;
+		goto unlock;
+	}
+
+	/*
+	 * Ensure that if we race with __stop_cpus() the stoppers won't get
+	 * queued up in reverse order leading to system deadlock.
+	 *
+	 * We can't miss stop_cpus_in_progress if queue_stop_cpus_work() has
+	 * queued a work on cpu1 but not on cpu2, we hold both locks.
+	 *
+	 * It can be falsely true but it is safe to spin until it is cleared,
+	 * queue_stop_cpus_work() does everything under preempt_disable().
+	 */
+	if (unlikely(stop_cpus_in_progress)) {
+		err = -EDEADLK;
+		goto unlock;
+	}
+
+	err = 0;
+	__cpu_stop_queue_work(stopper1, work1, &wakeq);
+	__cpu_stop_queue_work(stopper2, work2, &wakeq);
+
+unlock:
+	raw_spin_unlock(&stopper2->lock);
+	raw_spin_unlock_irq(&stopper1->lock);
+
+	if (unlikely(err == -EDEADLK)) {
+		preempt_enable();
+
+		while (stop_cpus_in_progress)
+			cpu_relax();
+
+		goto retry;
+	}
+
+	wake_up_q(&wakeq);
+	preempt_enable();
+
+	return err;
+}
+/**
+ * stop_two_cpus - stops two cpus
+ * @cpu1: the cpu to stop
+ * @cpu2: the other cpu to stop
+ * @fn: function to execute
+ * @arg: argument to @fn
+ *
+ * Stops both the current and specified CPU and runs @fn on one of them.
+ *
+ * returns when both are completed.
+ */
+int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg)
+{
+	struct cpu_stop_done done;
+	struct cpu_stop_work work1, work2;
+	struct multi_stop_data msdata;
+
+	msdata = (struct multi_stop_data){
+		.fn = fn,
+		.data = arg,
+		.num_threads = 2,
+		.active_cpus = cpumask_of(cpu1),
+	};
+
+	work1 = work2 = (struct cpu_stop_work){
+		.fn = multi_cpu_stop,
+		.arg = &msdata,
+		.done = &done
+	};
+
+	cpu_stop_init_done(&done, 2);
+	set_state(&msdata, MULTI_STOP_PREPARE);
+
+	if (cpu1 > cpu2)
+		swap(cpu1, cpu2);
+	if (cpu_stop_queue_two_works(cpu1, &work1, cpu2, &work2))
+		return -ENOENT;
+
+	wait_for_completion(&done.completion);
+	return done.ret;
+}
+
+/**
+ * stop_one_cpu_nowait - stop a cpu but don't wait for completion
+ * @cpu: cpu to stop
+ * @fn: function to execute
+ * @arg: argument to @fn
+ * @work_buf: pointer to cpu_stop_work structure
+ *
+ * Similar to stop_one_cpu() but doesn't wait for completion.  The
+ * caller is responsible for ensuring @work_buf is currently unused
+ * and will remain untouched until stopper starts executing @fn.
+ *
+ * CONTEXT:
+ * Don't care.
+ *
+ * RETURNS:
+ * true if cpu_stop_work was queued successfully and @fn will be called,
+ * false otherwise.
+ */
+bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
+			struct cpu_stop_work *work_buf)
+{
+	*work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, };
+	return cpu_stop_queue_work(cpu, work_buf);
+}
+
+static bool queue_stop_cpus_work(const struct cpumask *cpumask,
+				 cpu_stop_fn_t fn, void *arg,
+				 struct cpu_stop_done *done)
+{
+	struct cpu_stop_work *work;
+	unsigned int cpu;
+	bool queued = false;
+
+	/*
+	 * Disable preemption while queueing to avoid getting
+	 * preempted by a stopper which might wait for other stoppers
+	 * to enter @fn which can lead to deadlock.
+	 */
+	preempt_disable();
+	stop_cpus_in_progress = true;
+	for_each_cpu(cpu, cpumask) {
+		work = &per_cpu(cpu_stopper.stop_work, cpu);
+		work->fn = fn;
+		work->arg = arg;
+		work->done = done;
+		if (cpu_stop_queue_work(cpu, work))
+			queued = true;
+	}
+	stop_cpus_in_progress = false;
+	preempt_enable();
+
+	return queued;
+}
+
+static int __stop_cpus(const struct cpumask *cpumask,
+		       cpu_stop_fn_t fn, void *arg)
+{
+	struct cpu_stop_done done;
+
+	cpu_stop_init_done(&done, cpumask_weight(cpumask));
+	if (!queue_stop_cpus_work(cpumask, fn, arg, &done))
+		return -ENOENT;
+	wait_for_completion(&done.completion);
+	return done.ret;
+}
+
+/**
+ * stop_cpus - stop multiple cpus
+ * @cpumask: cpus to stop
+ * @fn: function to execute
+ * @arg: argument to @fn
+ *
+ * Execute @fn(@arg) on online cpus in @cpumask.  On each target cpu,
+ * @fn is run in a process context with the highest priority
+ * preempting any task on the cpu and monopolizing it.  This function
+ * returns after all executions are complete.
+ *
+ * This function doesn't guarantee the cpus in @cpumask stay online
+ * till @fn completes.  If some cpus go down in the middle, execution
+ * on the cpu may happen partially or fully on different cpus.  @fn
+ * should either be ready for that or the caller should ensure that
+ * the cpus stay online until this function completes.
+ *
+ * All stop_cpus() calls are serialized making it safe for @fn to wait
+ * for all cpus to start executing it.
+ *
+ * CONTEXT:
+ * Might sleep.
+ *
+ * RETURNS:
+ * -ENOENT if @fn(@arg) was not executed at all because all cpus in
+ * @cpumask were offline; otherwise, 0 if all executions of @fn
+ * returned 0, any non zero return value if any returned non zero.
+ */
+int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
+{
+	int ret;
+
+	/* static works are used, process one request at a time */
+	mutex_lock(&stop_cpus_mutex);
+	ret = __stop_cpus(cpumask, fn, arg);
+	mutex_unlock(&stop_cpus_mutex);
+	return ret;
+}
+
+/**
+ * try_stop_cpus - try to stop multiple cpus
+ * @cpumask: cpus to stop
+ * @fn: function to execute
+ * @arg: argument to @fn
+ *
+ * Identical to stop_cpus() except that it fails with -EAGAIN if
+ * someone else is already using the facility.
+ *
+ * CONTEXT:
+ * Might sleep.
+ *
+ * RETURNS:
+ * -EAGAIN if someone else is already stopping cpus, -ENOENT if
+ * @fn(@arg) was not executed at all because all cpus in @cpumask were
+ * offline; otherwise, 0 if all executions of @fn returned 0, any non
+ * zero return value if any returned non zero.
+ */
+int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
+{
+	int ret;
+
+	/* static works are used, process one request at a time */
+	if (!mutex_trylock(&stop_cpus_mutex))
+		return -EAGAIN;
+	ret = __stop_cpus(cpumask, fn, arg);
+	mutex_unlock(&stop_cpus_mutex);
+	return ret;
+}
+
+static int cpu_stop_should_run(unsigned int cpu)
+{
+	struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
+	unsigned long flags;
+	int run;
+
+	raw_spin_lock_irqsave(&stopper->lock, flags);
+	run = !list_empty(&stopper->works);
+	raw_spin_unlock_irqrestore(&stopper->lock, flags);
+	return run;
+}
+
+static void cpu_stopper_thread(unsigned int cpu)
+{
+	struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
+	struct cpu_stop_work *work;
+
+repeat:
+	work = NULL;
+	raw_spin_lock_irq(&stopper->lock);
+	if (!list_empty(&stopper->works)) {
+		work = list_first_entry(&stopper->works,
+					struct cpu_stop_work, list);
+		list_del_init(&work->list);
+	}
+	raw_spin_unlock_irq(&stopper->lock);
+
+	if (work) {
+		cpu_stop_fn_t fn = work->fn;
+		void *arg = work->arg;
+		struct cpu_stop_done *done = work->done;
+		int ret;
+
+		/* cpu stop callbacks must not sleep, make in_atomic() == T */
+		preempt_count_inc();
+		ret = fn(arg);
+		if (done) {
+			if (ret)
+				done->ret = ret;
+			cpu_stop_signal_done(done);
+		}
+		preempt_count_dec();
+		WARN_ONCE(preempt_count(),
+			  "cpu_stop: %pf(%p) leaked preempt count\n", fn, arg);
+		goto repeat;
+	}
+}
+
+void stop_machine_park(int cpu)
+{
+	struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
+	/*
+	 * Lockless. cpu_stopper_thread() will take stopper->lock and flush
+	 * the pending works before it parks, until then it is fine to queue
+	 * the new works.
+	 */
+	stopper->enabled = false;
+	kthread_park(stopper->thread);
+}
+
+extern void sched_set_stop_task(int cpu, struct task_struct *stop);
+
+static void cpu_stop_create(unsigned int cpu)
+{
+	sched_set_stop_task(cpu, per_cpu(cpu_stopper.thread, cpu));
+}
+
+static void cpu_stop_park(unsigned int cpu)
+{
+	struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
+
+	WARN_ON(!list_empty(&stopper->works));
+}
+
+void stop_machine_unpark(int cpu)
+{
+	struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
+
+	stopper->enabled = true;
+	kthread_unpark(stopper->thread);
+}
+
+static struct smp_hotplug_thread cpu_stop_threads = {
+	.store			= &cpu_stopper.thread,
+	.thread_should_run	= cpu_stop_should_run,
+	.thread_fn		= cpu_stopper_thread,
+	.thread_comm		= "migration/%u",
+	.create			= cpu_stop_create,
+	.park			= cpu_stop_park,
+	.selfparking		= true,
+};
+
+static int __init cpu_stop_init(void)
+{
+	unsigned int cpu;
+
+	for_each_possible_cpu(cpu) {
+		struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
+
+		raw_spin_lock_init(&stopper->lock);
+		INIT_LIST_HEAD(&stopper->works);
+	}
+
+	BUG_ON(smpboot_register_percpu_thread(&cpu_stop_threads));
+	stop_machine_unpark(raw_smp_processor_id());
+	stop_machine_initialized = true;
+	return 0;
+}
+early_initcall(cpu_stop_init);
+
+int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
+			    const struct cpumask *cpus)
+{
+	struct multi_stop_data msdata = {
+		.fn = fn,
+		.data = data,
+		.num_threads = num_online_cpus(),
+		.active_cpus = cpus,
+	};
+
+	lockdep_assert_cpus_held();
+
+	if (!stop_machine_initialized) {
+		/*
+		 * Handle the case where stop_machine() is called
+		 * early in boot before stop_machine() has been
+		 * initialized.
+		 */
+		unsigned long flags;
+		int ret;
+
+		WARN_ON_ONCE(msdata.num_threads != 1);
+
+		local_irq_save(flags);
+		hard_irq_disable();
+		ret = (*fn)(data);
+		local_irq_restore(flags);
+
+		return ret;
+	}
+
+	/* Set the initial state and stop all online cpus. */
+	set_state(&msdata, MULTI_STOP_PREPARE);
+	return stop_cpus(cpu_online_mask, multi_cpu_stop, &msdata);
+}
+
+int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
+{
+	int ret;
+
+	/* No CPUs can come up or down during this. */
+	cpus_read_lock();
+	ret = stop_machine_cpuslocked(fn, data, cpus);
+	cpus_read_unlock();
+	return ret;
+}
+EXPORT_SYMBOL_GPL(stop_machine);
+
+/**
+ * stop_machine_from_inactive_cpu - stop_machine() from inactive CPU
+ * @fn: the function to run
+ * @data: the data ptr for the @fn()
+ * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
+ *
+ * This is identical to stop_machine() but can be called from a CPU which
+ * is not active.  The local CPU is in the process of hotplug (so no other
+ * CPU hotplug can start) and not marked active and doesn't have enough
+ * context to sleep.
+ *
+ * This function provides stop_machine() functionality for such state by
+ * using busy-wait for synchronization and executing @fn directly for local
+ * CPU.
+ *
+ * CONTEXT:
+ * Local CPU is inactive.  Temporarily stops all active CPUs.
+ *
+ * RETURNS:
+ * 0 if all executions of @fn returned 0, any non zero return value if any
+ * returned non zero.
+ */
+int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
+				  const struct cpumask *cpus)
+{
+	struct multi_stop_data msdata = { .fn = fn, .data = data,
+					    .active_cpus = cpus };
+	struct cpu_stop_done done;
+	int ret;
+
+	/* Local CPU must be inactive and CPU hotplug in progress. */
+	BUG_ON(cpu_active(raw_smp_processor_id()));
+	msdata.num_threads = num_active_cpus() + 1;	/* +1 for local */
+
+	/* No proper task established and can't sleep - busy wait for lock. */
+	while (!mutex_trylock(&stop_cpus_mutex))
+		cpu_relax();
+
+	/* Schedule work on other CPUs and execute directly for local CPU */
+	set_state(&msdata, MULTI_STOP_PREPARE);
+	cpu_stop_init_done(&done, num_active_cpus());
+	queue_stop_cpus_work(cpu_active_mask, multi_cpu_stop, &msdata,
+			     &done);
+	ret = multi_cpu_stop(&msdata);
+
+	/* Busy wait for completion. */
+	while (!completion_done(&done.completion))
+		cpu_relax();
+
+	mutex_unlock(&stop_cpus_mutex);
+	return ret ?: done.ret;
+}