linux-next/kernel/scftorture.c

// SPDX-License-Identifier: GPL-2.0+
//
// Torture test for smp_call_function() and friends.
//
// Copyright (C) Facebook, 2020.
//
// Author: Paul E. McKenney <paulmck@kernel.org>

#define pr_fmt(fmt) fmt

#include <linux/atomic.h>
#include <linux/bitops.h>
#include <linux/completion.h>
#include <linux/cpu.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/kthread.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/notifier.h>
#include <linux/percpu.h>
#include <linux/rcupdate.h>
#include <linux/rcupdate_trace.h>
#include <linux/reboot.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/stat.h>
#include <linux/srcu.h>
#include <linux/slab.h>
#include <linux/torture.h>
#include <linux/types.h>

#define SCFTORT_STRING "scftorture"
#define SCFTORT_FLAG SCFTORT_STRING ": "

#define SCFTORTOUT(s, x...) \
	pr_alert(SCFTORT_FLAG s, ## x)

#define VERBOSE_SCFTORTOUT(s, x...) \
	do { if (verbose) pr_alert(SCFTORT_FLAG s, ## x); } while (0)

#define VERBOSE_SCFTORTOUT_ERRSTRING(s, x...) \
	do { if (verbose) pr_alert(SCFTORT_FLAG "!!! " s, ## x); } while (0)

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Paul E. McKenney <paulmck@kernel.org>");

// Wait until there are multiple CPUs before starting test.
torture_param(int, holdoff, IS_BUILTIN(CONFIG_SCF_TORTURE_TEST) ? 10 : 0,
	      "Holdoff time before test start (s)");
torture_param(int, longwait, 0, "Include ridiculously long waits? (seconds)");
torture_param(int, nthreads, -1, "# threads, defaults to -1 for all CPUs.");
torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
torture_param(int, onoff_interval, 0, "Time between CPU hotplugs (s), 0=disable");
torture_param(int, shutdown_secs, 0, "Shutdown time (ms), <= zero to disable.");
torture_param(int, stat_interval, 60, "Number of seconds between stats printk()s.");
torture_param(int, stutter_cpus, 5, "Number of jiffies to change CPUs under test, 0=disable");
torture_param(bool, use_cpus_read_lock, 0, "Use cpus_read_lock() to exclude CPU hotplug.");
torture_param(int, verbose, 0, "Enable verbose debugging printk()s");
torture_param(int, weight_single, -1, "Testing weight for single-CPU no-wait operations.");
torture_param(int, weight_single_wait, -1, "Testing weight for single-CPU operations.");
torture_param(int, weight_mult, -1, "Testing weight for multi-CPU no-wait operations.");
torture_param(int, weight_mult_wait, -1, "Testing weight for multi-CPU operations.");
torture_param(int, weight_all, -1, "Testing weight for all-CPU no-wait operations.");
torture_param(int, weight_all_wait, -1, "Testing weight for all-CPU operations.");

char *torture_type = "";

#ifdef MODULE
# define SCFTORT_SHUTDOWN 0
#else
# define SCFTORT_SHUTDOWN 1
#endif

torture_param(bool, shutdown, SCFTORT_SHUTDOWN, "Shutdown at end of torture test.");

struct scf_statistics {
	struct task_struct *task;
	int cpu;
	long long n_single;
	long long n_single_wait;
	long long n_multi;
	long long n_multi_wait;
	long long n_all;
	long long n_all_wait;
};

static struct scf_statistics *scf_stats_p;
static struct task_struct *scf_torture_stats_task;
static DEFINE_PER_CPU(long long, scf_invoked_count);

// Use to wait for all threads to start.
static atomic_t n_started;
static atomic_t n_errs;
static bool scfdone;

DEFINE_TORTURE_RANDOM_PERCPU(scf_torture_rand);

// Print torture statistics.  Caller must ensure serialization.
static void scf_torture_stats_print(void)
{
	int cpu;
	long long invoked_count = 0;
	bool isdone = READ_ONCE(scfdone);

	for_each_possible_cpu(cpu)
		invoked_count += data_race(per_cpu(scf_invoked_count, cpu));
	pr_alert("%s scf_invoked_count %s: %lld ",
		 SCFTORT_FLAG, isdone ? "VER" : "ver", invoked_count);
	torture_onoff_stats();
	pr_cont("\n");
}

// Periodically prints torture statistics, if periodic statistics printing
// was specified via the stat_interval module parameter.
static int
scf_torture_stats(void *arg)
{
	VERBOSE_TOROUT_STRING("scf_torture_stats task started");
	do {
		schedule_timeout_interruptible(stat_interval * HZ);
		scf_torture_stats_print();
		torture_shutdown_absorb("scf_torture_stats");
	} while (!torture_must_stop());
	torture_kthread_stopping("scf_torture_stats");
	return 0;
}

// Update statistics and occasionally burn up mass quantities of CPU time,
// if told to do so via scftorture.longwait.  Otherwise, occasionally burn
// a little bit.
static void scf_handler(void *unused)
{
	int i;
	int j;
	unsigned long r = torture_random(this_cpu_ptr(&scf_torture_rand));

	this_cpu_inc(scf_invoked_count);
	if (longwait <= 0) {
		if (!(r & 0xffc0))
			udelay(r & 0x3f);
		return;
	}
	if (r & 0xfff)
		return;
	r = (r >> 12);
	if (longwait <= 0) {
		udelay((r & 0xff) + 1);
		return;
	}
	r = r % longwait + 1;
	for (i = 0; i < r; i++) {
		for (j = 0; j < 1000; j++) {
			udelay(1000);
			cpu_relax();
		}
	}
}

// Randomly do an smp_call_function*() invocation.
static void scftorture_invoke_one(struct scf_statistics *scfp,struct torture_random_state *trsp)
{
	if (use_cpus_read_lock)
		cpus_read_lock();
	else
		preempt_disable();
	scfp->n_all++;
	smp_call_function(scf_handler, NULL, 0);
	if (use_cpus_read_lock)
		cpus_read_unlock();
	else
		preempt_enable();
	if (!(torture_random(trsp) & 0xfff))
		schedule_timeout_uninterruptible(1);
}

// SCF test kthread.  Repeatedly does calls to members of the
// smp_call_function() family of functions.
static int scftorture_invoker(void *arg)
{
	DEFINE_TORTURE_RANDOM(rand);
	struct scf_statistics *scfp = (struct scf_statistics *)arg;

	VERBOSE_SCFTORTOUT("scftorture_invoker %d: task started", scfp->cpu);
	set_cpus_allowed_ptr(current, cpumask_of(scfp->cpu % nr_cpu_ids));
	set_user_nice(current, MAX_NICE);
	if (holdoff)
		schedule_timeout_interruptible(holdoff * HZ);

	VERBOSE_SCFTORTOUT("scftorture_invoker %d: Waiting for all SCF torturers from cpu %d", scfp->cpu, smp_processor_id());

	// Make sure that the CPU is affinitized appropriately during testing.
	WARN_ON_ONCE(smp_processor_id() != scfp->cpu);

	if (!atomic_dec_return(&n_started))
		while (atomic_read_acquire(&n_started)) {
			if (torture_must_stop()) {
				VERBOSE_SCFTORTOUT("scftorture_invoker %d ended before starting", scfp->cpu);
				goto end;
			}
			schedule_timeout_uninterruptible(1);
		}

	VERBOSE_SCFTORTOUT("scftorture_invoker %d started", scfp->cpu);

	do {
		scftorture_invoke_one(scfp, &rand);
	} while (!torture_must_stop());

	VERBOSE_SCFTORTOUT("scftorture_invoker %d ended", scfp->cpu);
end:
	torture_kthread_stopping("scftorture_invoker");
	return 0;
}

static void
scftorture_print_module_parms(const char *tag)
{
	pr_alert(SCFTORT_FLAG
		 "--- %s:  verbose=%d holdoff=%d longwait=%d nthreads=%d onoff_holdoff=%d onoff_interval=%d shutdown_secs=%d stat_interval=%d stutter_cpus=%d use_cpus_read_lock=%d, weight_single=%d, weight_single_wait=%d, weight_mult=%d, weight_mult_wait=%d, weight_all=%d, weight_all_wait=%d\n", tag,
		 verbose, holdoff, longwait, nthreads, onoff_holdoff, onoff_interval, shutdown, stat_interval, stutter_cpus, use_cpus_read_lock, weight_single, weight_single_wait, weight_mult, weight_mult_wait, weight_all, weight_all_wait);
}

static void scf_cleanup_handler(void *unused)
{
}

static void scf_torture_cleanup(void)
{
	int i;

	if (torture_cleanup_begin())
		return;

	WRITE_ONCE(scfdone, true);
	if (nthreads)
		for (i = 0; i < nthreads; i++)
			torture_stop_kthread("scftorture_invoker", scf_stats_p[i].task);
	else
		goto end;
	kfree(scf_stats_p);
	scf_stats_p = NULL;
	smp_call_function(scf_cleanup_handler, NULL, 0);
	torture_stop_kthread(scf_torture_stats, scf_torture_stats_task);
	scf_torture_stats_print();  // -After- the stats thread is stopped!

	if (atomic_read(&n_errs))
		scftorture_print_module_parms("End of test: FAILURE");
	else if (torture_onoff_failures())
		scftorture_print_module_parms("End of test: LOCK_HOTPLUG");
	else
		scftorture_print_module_parms("End of test: SUCCESS");

end:
	torture_cleanup_end();
}

static int __init scf_torture_init(void)
{
	long i;
	int firsterr = 0;

	if (!torture_init_begin(SCFTORT_STRING, verbose))
		return -EBUSY;

	scftorture_print_module_parms("Start of test");

	if (weight_single == -1 && weight_single_wait == -1 &&
	    weight_mult == -1 && weight_mult_wait == -1 &&
	    weight_all == -1 && weight_all_wait == -1) {
		weight_single = 1;
		weight_single_wait = 1;
		weight_mult = 1;
		weight_mult_wait = 1;
		weight_all = 1;
		weight_all_wait = 1;
	} else {
		if (weight_single == -1)
			weight_single = 0;
		if (weight_single_wait == -1)
			weight_single_wait = 0;
		if (weight_mult == -1)
			weight_mult = 0;
		if (weight_mult_wait == -1)
			weight_mult_wait = 0;
		if (weight_all == -1)
			weight_all = 0;
		if (weight_all_wait == -1)
			weight_all_wait = 0;
	}
	if (weight_single == 0 && weight_single_wait == 0 &&
	    weight_mult == 0 && weight_mult_wait == 0 &&
	    weight_all == 0 && weight_all_wait == 0) {
		firsterr = -EINVAL;
		goto unwind;
	}

	if (onoff_interval > 0) {
		firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval, NULL);
		if (firsterr)
			goto unwind;
	}
	if (shutdown_secs > 0) {
		firsterr = torture_shutdown_init(shutdown_secs, scf_torture_cleanup);
		if (firsterr)
			goto unwind;
	}

	// Worker tasks invoking smp_call_function().
	if (nthreads < 0)
		nthreads = num_online_cpus();
	scf_stats_p = kcalloc(nthreads, sizeof(scf_stats_p[0]), GFP_KERNEL);
	if (!scf_stats_p) {
		VERBOSE_SCFTORTOUT_ERRSTRING("out of memory");
		firsterr = -ENOMEM;
		goto unwind;
	}

	VERBOSE_SCFTORTOUT("Starting %d smp_call_function() threads\n", nthreads);

	atomic_set(&n_started, nthreads);
	for (i = 0; i < nthreads; i++) {
		scf_stats_p[i].cpu = i;
		firsterr = torture_create_kthread(scftorture_invoker, (void *)&scf_stats_p[i],
						  scf_stats_p[i].task);
		if (firsterr)
			goto unwind;
	}
	if (stat_interval > 0) {
		firsterr = torture_create_kthread(scf_torture_stats, NULL, scf_torture_stats_task);
		if (firsterr)
			goto unwind;
	}

	torture_init_end();
	return 0;

unwind:
	torture_init_end();
	scf_torture_cleanup();
	return firsterr;
}

module_init(scf_torture_init);
module_exit(scf_torture_cleanup);