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f7951c33f0
Pull scheduler updates from Thomas Gleixner: - Cleanup and improvement of NUMA balancing - Refactoring and improvements to the PELT (Per Entity Load Tracking) code - Watchdog simplification and related cleanups - The usual pile of small incremental fixes and improvements * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (41 commits) watchdog: Reduce message verbosity stop_machine: Reflow cpu_stop_queue_two_works() sched/numa: Move task_numa_placement() closer to numa_migrate_preferred() sched/numa: Use group_weights to identify if migration degrades locality sched/numa: Update the scan period without holding the numa_group lock sched/numa: Remove numa_has_capacity() sched/numa: Modify migrate_swap() to accept additional parameters sched/numa: Remove unused task_capacity from 'struct numa_stats' sched/numa: Skip nodes that are at 'hoplimit' sched/debug: Reverse the order of printing faults sched/numa: Use task faults only if numa_group is not yet set up sched/numa: Set preferred_node based on best_cpu sched/numa: Simplify load_too_imbalanced() sched/numa: Evaluate move once per node sched/numa: Remove redundant field sched/debug: Show the sum wait time of a task group sched/fair: Remove #ifdefs from scale_rt_capacity() sched/core: Remove get_cpu() from sched_fork() sched/cpufreq: Clarify sugov_get_util() sched/sysctl: Remove unused sched_time_avg_ms sysctl ...
683 lines
18 KiB
C
683 lines
18 KiB
C
/*
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* kernel/stop_machine.c
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*
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* Copyright (C) 2008, 2005 IBM Corporation.
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* Copyright (C) 2008, 2005 Rusty Russell rusty@rustcorp.com.au
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* Copyright (C) 2010 SUSE Linux Products GmbH
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* Copyright (C) 2010 Tejun Heo <tj@kernel.org>
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*
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* This file is released under the GPLv2 and any later version.
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*/
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#include <linux/completion.h>
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#include <linux/cpu.h>
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#include <linux/init.h>
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#include <linux/kthread.h>
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#include <linux/export.h>
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#include <linux/percpu.h>
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#include <linux/sched.h>
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#include <linux/stop_machine.h>
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#include <linux/interrupt.h>
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#include <linux/kallsyms.h>
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#include <linux/smpboot.h>
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#include <linux/atomic.h>
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#include <linux/nmi.h>
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#include <linux/sched/wake_q.h>
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/*
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* Structure to determine completion condition and record errors. May
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* be shared by works on different cpus.
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*/
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struct cpu_stop_done {
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atomic_t nr_todo; /* nr left to execute */
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int ret; /* collected return value */
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struct completion completion; /* fired if nr_todo reaches 0 */
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};
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/* the actual stopper, one per every possible cpu, enabled on online cpus */
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struct cpu_stopper {
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struct task_struct *thread;
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raw_spinlock_t lock;
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bool enabled; /* is this stopper enabled? */
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struct list_head works; /* list of pending works */
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struct cpu_stop_work stop_work; /* for stop_cpus */
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};
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static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper);
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static bool stop_machine_initialized = false;
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/* static data for stop_cpus */
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static DEFINE_MUTEX(stop_cpus_mutex);
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static bool stop_cpus_in_progress;
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static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo)
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{
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memset(done, 0, sizeof(*done));
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atomic_set(&done->nr_todo, nr_todo);
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init_completion(&done->completion);
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}
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/* signal completion unless @done is NULL */
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static void cpu_stop_signal_done(struct cpu_stop_done *done)
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{
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if (atomic_dec_and_test(&done->nr_todo))
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complete(&done->completion);
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}
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static void __cpu_stop_queue_work(struct cpu_stopper *stopper,
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struct cpu_stop_work *work,
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struct wake_q_head *wakeq)
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{
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list_add_tail(&work->list, &stopper->works);
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wake_q_add(wakeq, stopper->thread);
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}
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/* queue @work to @stopper. if offline, @work is completed immediately */
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static bool cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work)
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{
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struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
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DEFINE_WAKE_Q(wakeq);
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unsigned long flags;
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bool enabled;
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preempt_disable();
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raw_spin_lock_irqsave(&stopper->lock, flags);
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enabled = stopper->enabled;
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if (enabled)
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__cpu_stop_queue_work(stopper, work, &wakeq);
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else if (work->done)
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cpu_stop_signal_done(work->done);
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raw_spin_unlock_irqrestore(&stopper->lock, flags);
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wake_up_q(&wakeq);
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preempt_enable();
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return enabled;
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}
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/**
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* stop_one_cpu - stop a cpu
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* @cpu: cpu to stop
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* @fn: function to execute
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* @arg: argument to @fn
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*
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* Execute @fn(@arg) on @cpu. @fn is run in a process context with
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* the highest priority preempting any task on the cpu and
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* monopolizing it. This function returns after the execution is
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* complete.
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*
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* This function doesn't guarantee @cpu stays online till @fn
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* completes. If @cpu goes down in the middle, execution may happen
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* partially or fully on different cpus. @fn should either be ready
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* for that or the caller should ensure that @cpu stays online until
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* this function completes.
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*
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* CONTEXT:
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* Might sleep.
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*
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* RETURNS:
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* -ENOENT if @fn(@arg) was not executed because @cpu was offline;
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* otherwise, the return value of @fn.
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*/
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int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
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{
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struct cpu_stop_done done;
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struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done };
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cpu_stop_init_done(&done, 1);
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if (!cpu_stop_queue_work(cpu, &work))
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return -ENOENT;
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/*
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* In case @cpu == smp_proccessor_id() we can avoid a sleep+wakeup
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* cycle by doing a preemption:
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*/
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cond_resched();
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wait_for_completion(&done.completion);
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return done.ret;
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}
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/* This controls the threads on each CPU. */
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enum multi_stop_state {
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/* Dummy starting state for thread. */
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MULTI_STOP_NONE,
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/* Awaiting everyone to be scheduled. */
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MULTI_STOP_PREPARE,
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/* Disable interrupts. */
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MULTI_STOP_DISABLE_IRQ,
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/* Run the function */
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MULTI_STOP_RUN,
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/* Exit */
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MULTI_STOP_EXIT,
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};
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struct multi_stop_data {
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cpu_stop_fn_t fn;
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void *data;
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/* Like num_online_cpus(), but hotplug cpu uses us, so we need this. */
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unsigned int num_threads;
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const struct cpumask *active_cpus;
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enum multi_stop_state state;
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atomic_t thread_ack;
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};
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static void set_state(struct multi_stop_data *msdata,
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enum multi_stop_state newstate)
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{
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/* Reset ack counter. */
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atomic_set(&msdata->thread_ack, msdata->num_threads);
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smp_wmb();
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msdata->state = newstate;
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}
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/* Last one to ack a state moves to the next state. */
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static void ack_state(struct multi_stop_data *msdata)
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{
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if (atomic_dec_and_test(&msdata->thread_ack))
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set_state(msdata, msdata->state + 1);
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}
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/* This is the cpu_stop function which stops the CPU. */
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static int multi_cpu_stop(void *data)
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{
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struct multi_stop_data *msdata = data;
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enum multi_stop_state curstate = MULTI_STOP_NONE;
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int cpu = smp_processor_id(), err = 0;
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unsigned long flags;
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bool is_active;
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/*
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* When called from stop_machine_from_inactive_cpu(), irq might
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* already be disabled. Save the state and restore it on exit.
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*/
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local_save_flags(flags);
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if (!msdata->active_cpus)
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is_active = cpu == cpumask_first(cpu_online_mask);
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else
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is_active = cpumask_test_cpu(cpu, msdata->active_cpus);
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/* Simple state machine */
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do {
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/* Chill out and ensure we re-read multi_stop_state. */
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cpu_relax_yield();
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if (msdata->state != curstate) {
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curstate = msdata->state;
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switch (curstate) {
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case MULTI_STOP_DISABLE_IRQ:
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local_irq_disable();
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hard_irq_disable();
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break;
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case MULTI_STOP_RUN:
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if (is_active)
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err = msdata->fn(msdata->data);
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break;
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default:
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break;
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}
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ack_state(msdata);
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} else if (curstate > MULTI_STOP_PREPARE) {
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/*
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* At this stage all other CPUs we depend on must spin
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* in the same loop. Any reason for hard-lockup should
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* be detected and reported on their side.
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*/
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touch_nmi_watchdog();
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}
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} while (curstate != MULTI_STOP_EXIT);
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local_irq_restore(flags);
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return err;
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}
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static int cpu_stop_queue_two_works(int cpu1, struct cpu_stop_work *work1,
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int cpu2, struct cpu_stop_work *work2)
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{
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struct cpu_stopper *stopper1 = per_cpu_ptr(&cpu_stopper, cpu1);
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struct cpu_stopper *stopper2 = per_cpu_ptr(&cpu_stopper, cpu2);
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DEFINE_WAKE_Q(wakeq);
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int err;
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retry:
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/*
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* The waking up of stopper threads has to happen in the same
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* scheduling context as the queueing. Otherwise, there is a
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* possibility of one of the above stoppers being woken up by another
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* CPU, and preempting us. This will cause us to not wake up the other
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* stopper forever.
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*/
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preempt_disable();
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raw_spin_lock_irq(&stopper1->lock);
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raw_spin_lock_nested(&stopper2->lock, SINGLE_DEPTH_NESTING);
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if (!stopper1->enabled || !stopper2->enabled) {
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err = -ENOENT;
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goto unlock;
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}
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/*
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* Ensure that if we race with __stop_cpus() the stoppers won't get
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* queued up in reverse order leading to system deadlock.
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*
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* We can't miss stop_cpus_in_progress if queue_stop_cpus_work() has
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* queued a work on cpu1 but not on cpu2, we hold both locks.
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*
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* It can be falsely true but it is safe to spin until it is cleared,
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* queue_stop_cpus_work() does everything under preempt_disable().
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*/
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if (unlikely(stop_cpus_in_progress)) {
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err = -EDEADLK;
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goto unlock;
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}
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err = 0;
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__cpu_stop_queue_work(stopper1, work1, &wakeq);
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__cpu_stop_queue_work(stopper2, work2, &wakeq);
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unlock:
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raw_spin_unlock(&stopper2->lock);
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raw_spin_unlock_irq(&stopper1->lock);
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if (unlikely(err == -EDEADLK)) {
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preempt_enable();
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while (stop_cpus_in_progress)
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cpu_relax();
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goto retry;
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}
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wake_up_q(&wakeq);
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preempt_enable();
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return err;
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}
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/**
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* stop_two_cpus - stops two cpus
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* @cpu1: the cpu to stop
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* @cpu2: the other cpu to stop
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* @fn: function to execute
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* @arg: argument to @fn
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*
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* Stops both the current and specified CPU and runs @fn on one of them.
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*
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* returns when both are completed.
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*/
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int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg)
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{
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struct cpu_stop_done done;
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struct cpu_stop_work work1, work2;
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struct multi_stop_data msdata;
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msdata = (struct multi_stop_data){
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.fn = fn,
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.data = arg,
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.num_threads = 2,
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.active_cpus = cpumask_of(cpu1),
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};
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work1 = work2 = (struct cpu_stop_work){
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.fn = multi_cpu_stop,
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.arg = &msdata,
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.done = &done
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};
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cpu_stop_init_done(&done, 2);
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set_state(&msdata, MULTI_STOP_PREPARE);
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if (cpu1 > cpu2)
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swap(cpu1, cpu2);
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if (cpu_stop_queue_two_works(cpu1, &work1, cpu2, &work2))
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return -ENOENT;
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wait_for_completion(&done.completion);
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return done.ret;
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}
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/**
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* stop_one_cpu_nowait - stop a cpu but don't wait for completion
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* @cpu: cpu to stop
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* @fn: function to execute
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* @arg: argument to @fn
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* @work_buf: pointer to cpu_stop_work structure
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*
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* Similar to stop_one_cpu() but doesn't wait for completion. The
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* caller is responsible for ensuring @work_buf is currently unused
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* and will remain untouched until stopper starts executing @fn.
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*
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* CONTEXT:
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* Don't care.
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*
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* RETURNS:
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* true if cpu_stop_work was queued successfully and @fn will be called,
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* false otherwise.
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*/
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bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
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struct cpu_stop_work *work_buf)
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{
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*work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, };
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return cpu_stop_queue_work(cpu, work_buf);
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}
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static bool queue_stop_cpus_work(const struct cpumask *cpumask,
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cpu_stop_fn_t fn, void *arg,
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struct cpu_stop_done *done)
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{
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struct cpu_stop_work *work;
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unsigned int cpu;
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bool queued = false;
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/*
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* Disable preemption while queueing to avoid getting
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* preempted by a stopper which might wait for other stoppers
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* to enter @fn which can lead to deadlock.
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*/
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preempt_disable();
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stop_cpus_in_progress = true;
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for_each_cpu(cpu, cpumask) {
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work = &per_cpu(cpu_stopper.stop_work, cpu);
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work->fn = fn;
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work->arg = arg;
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work->done = done;
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if (cpu_stop_queue_work(cpu, work))
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queued = true;
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}
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stop_cpus_in_progress = false;
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preempt_enable();
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return queued;
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}
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static int __stop_cpus(const struct cpumask *cpumask,
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cpu_stop_fn_t fn, void *arg)
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{
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struct cpu_stop_done done;
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cpu_stop_init_done(&done, cpumask_weight(cpumask));
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if (!queue_stop_cpus_work(cpumask, fn, arg, &done))
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return -ENOENT;
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wait_for_completion(&done.completion);
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return done.ret;
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}
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/**
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* stop_cpus - stop multiple cpus
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* @cpumask: cpus to stop
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* @fn: function to execute
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* @arg: argument to @fn
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*
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* Execute @fn(@arg) on online cpus in @cpumask. On each target cpu,
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* @fn is run in a process context with the highest priority
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* preempting any task on the cpu and monopolizing it. This function
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* returns after all executions are complete.
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*
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* This function doesn't guarantee the cpus in @cpumask stay online
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* till @fn completes. If some cpus go down in the middle, execution
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* on the cpu may happen partially or fully on different cpus. @fn
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* should either be ready for that or the caller should ensure that
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* the cpus stay online until this function completes.
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*
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* All stop_cpus() calls are serialized making it safe for @fn to wait
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* for all cpus to start executing it.
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*
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* CONTEXT:
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* Might sleep.
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*
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* RETURNS:
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* -ENOENT if @fn(@arg) was not executed at all because all cpus in
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* @cpumask were offline; otherwise, 0 if all executions of @fn
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* returned 0, any non zero return value if any returned non zero.
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*/
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int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
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{
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int ret;
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/* static works are used, process one request at a time */
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mutex_lock(&stop_cpus_mutex);
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ret = __stop_cpus(cpumask, fn, arg);
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mutex_unlock(&stop_cpus_mutex);
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return ret;
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}
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/**
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* try_stop_cpus - try to stop multiple cpus
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* @cpumask: cpus to stop
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* @fn: function to execute
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* @arg: argument to @fn
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*
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* Identical to stop_cpus() except that it fails with -EAGAIN if
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* someone else is already using the facility.
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*
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* CONTEXT:
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* Might sleep.
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*
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* RETURNS:
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* -EAGAIN if someone else is already stopping cpus, -ENOENT if
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* @fn(@arg) was not executed at all because all cpus in @cpumask were
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* offline; otherwise, 0 if all executions of @fn returned 0, any non
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* zero return value if any returned non zero.
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*/
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int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
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{
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int ret;
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/* static works are used, process one request at a time */
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if (!mutex_trylock(&stop_cpus_mutex))
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return -EAGAIN;
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ret = __stop_cpus(cpumask, fn, arg);
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mutex_unlock(&stop_cpus_mutex);
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return ret;
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}
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static int cpu_stop_should_run(unsigned int cpu)
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{
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struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
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unsigned long flags;
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int run;
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raw_spin_lock_irqsave(&stopper->lock, flags);
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run = !list_empty(&stopper->works);
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raw_spin_unlock_irqrestore(&stopper->lock, flags);
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return run;
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}
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static void cpu_stopper_thread(unsigned int cpu)
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{
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struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
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|
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;
|
|
}
|