// 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_many, -1, "Testing weight for multi-CPU no-wait operations.");
  torture_param(int, weight_many_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_ofl;

  	long long n_single_wait;

  	long long n_single_wait_ofl;
  	long long n_many;
  	long long n_many_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);

  // Data for random primitive selection
  #define SCF_PRIM_SINGLE		0
  #define SCF_PRIM_MANY		1
  #define SCF_PRIM_ALL		2
  #define SCF_NPRIMS		(2 * 3) // Need wait and no-wait versions of each.
  
  static char *scf_prim_name[] = {
  	"smp_call_function_single",
  	"smp_call_function_many",
  	"smp_call_function",
  };
  
  struct scf_selector {
  	unsigned long scfs_weight;
  	int scfs_prim;
  	bool scfs_wait;
  };
  static struct scf_selector scf_sel_array[SCF_NPRIMS];
  static int scf_sel_array_len;
  static unsigned long scf_sel_totweight;

  // Communicate between caller and handler.
  struct scf_check {
  	bool scfc_in;
  	bool scfc_out;
  	int scfc_cpu; // -1 for not _single().
  	bool scfc_wait;
  };

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

  static atomic_t n_mb_in_errs;
  static atomic_t n_mb_out_errs;
  static atomic_t n_alloc_errs;

  static bool scfdone;

  static char *bangstr = "";

  static DEFINE_TORTURE_RANDOM_PERCPU(scf_torture_rand);

  
  // Print torture statistics.  Caller must ensure serialization.
  static void scf_torture_stats_print(void)
  {
  	int cpu;

  	int i;

  	long long invoked_count = 0;
  	bool isdone = READ_ONCE(scfdone);

  	struct scf_statistics scfs = {};

  
  	for_each_possible_cpu(cpu)
  		invoked_count += data_race(per_cpu(scf_invoked_count, cpu));

  	for (i = 0; i < nthreads; i++) {
  		scfs.n_single += scf_stats_p[i].n_single;
  		scfs.n_single_ofl += scf_stats_p[i].n_single_ofl;
  		scfs.n_single_wait += scf_stats_p[i].n_single_wait;
  		scfs.n_single_wait_ofl += scf_stats_p[i].n_single_wait_ofl;
  		scfs.n_many += scf_stats_p[i].n_many;
  		scfs.n_many_wait += scf_stats_p[i].n_many_wait;
  		scfs.n_all += scf_stats_p[i].n_all;
  		scfs.n_all_wait += scf_stats_p[i].n_all_wait;
  	}

  	if (atomic_read(&n_errs) || atomic_read(&n_mb_in_errs) ||
  	    atomic_read(&n_mb_out_errs) || atomic_read(&n_alloc_errs))
  		bangstr = "!!! ";
  	pr_alert("%s %sscf_invoked_count %s: %lld single: %lld/%lld single_ofl: %lld/%lld many: %lld/%lld all: %lld/%lld ",
  		 SCFTORT_FLAG, bangstr, isdone ? "VER" : "ver", invoked_count,

  		 scfs.n_single, scfs.n_single_wait, scfs.n_single_ofl, scfs.n_single_wait_ofl,
  		 scfs.n_many, scfs.n_many_wait, scfs.n_all, scfs.n_all_wait);

  	torture_onoff_stats();

  	pr_cont("ste: %d stnmie: %d stnmoe: %d staf: %d
  ", atomic_read(&n_errs),
  		atomic_read(&n_mb_in_errs), atomic_read(&n_mb_out_errs),
  		atomic_read(&n_alloc_errs));

  }
  
  // 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;
  }

  // Add a primitive to the scf_sel_array[].
  static void scf_sel_add(unsigned long weight, int prim, bool wait)
  {
  	struct scf_selector *scfsp = &scf_sel_array[scf_sel_array_len];
  
  	// If no weight, if array would overflow, if computing three-place
  	// percentages would overflow, or if the scf_prim_name[] array would
  	// overflow, don't bother.  In the last three two cases, complain.
  	if (!weight ||
  	    WARN_ON_ONCE(scf_sel_array_len >= ARRAY_SIZE(scf_sel_array)) ||
  	    WARN_ON_ONCE(0 - 100000 * weight <= 100000 * scf_sel_totweight) ||
  	    WARN_ON_ONCE(prim >= ARRAY_SIZE(scf_prim_name)))
  		return;
  	scf_sel_totweight += weight;
  	scfsp->scfs_weight = scf_sel_totweight;
  	scfsp->scfs_prim = prim;
  	scfsp->scfs_wait = wait;
  	scf_sel_array_len++;
  }
  
  // Dump out weighting percentages for scf_prim_name[] array.
  static void scf_sel_dump(void)
  {
  	int i;
  	unsigned long oldw = 0;
  	struct scf_selector *scfsp;
  	unsigned long w;
  
  	for (i = 0; i < scf_sel_array_len; i++) {
  		scfsp = &scf_sel_array[i];
  		w = (scfsp->scfs_weight - oldw) * 100000 / scf_sel_totweight;
  		pr_info("%s: %3lu.%03lu %s(%s)
  ", __func__, w / 1000, w % 1000,
  			scf_prim_name[scfsp->scfs_prim],
  			scfsp->scfs_wait ? "wait" : "nowait");
  		oldw = scfsp->scfs_weight;
  	}
  }
  
  // Randomly pick a primitive and wait/nowait, based on weightings.
  static struct scf_selector *scf_sel_rand(struct torture_random_state *trsp)
  {
  	int i;
  	unsigned long w = torture_random(trsp) % (scf_sel_totweight + 1);
  
  	for (i = 0; i < scf_sel_array_len; i++)
  		if (scf_sel_array[i].scfs_weight >= w)
  			return &scf_sel_array[i];
  	WARN_ON_ONCE(1);
  	return &scf_sel_array[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 *scfc_in)

  {
  	int i;
  	int j;
  	unsigned long r = torture_random(this_cpu_ptr(&scf_torture_rand));

  	struct scf_check *scfcp = scfc_in;

  	if (likely(scfcp)) {
  		WRITE_ONCE(scfcp->scfc_out, false); // For multiple receivers.
  		if (WARN_ON_ONCE(unlikely(!READ_ONCE(scfcp->scfc_in))))
  			atomic_inc(&n_mb_in_errs);
  	}

  	this_cpu_inc(scf_invoked_count);
  	if (longwait <= 0) {
  		if (!(r & 0xffc0))
  			udelay(r & 0x3f);

  		goto out;

  	}
  	if (r & 0xfff)

  		goto out;

  	r = (r >> 12);
  	if (longwait <= 0) {
  		udelay((r & 0xff) + 1);

  		goto out;

  	}
  	r = r % longwait + 1;
  	for (i = 0; i < r; i++) {
  		for (j = 0; j < 1000; j++) {
  			udelay(1000);
  			cpu_relax();
  		}
  	}

  out:
  	if (unlikely(!scfcp))
  		return;
  	if (scfcp->scfc_wait)
  		WRITE_ONCE(scfcp->scfc_out, true);
  	else
  		kfree(scfcp);

  }

  // As above, but check for correct CPU.

  static void scf_handler_1(void *scfc_in)

  {

  	struct scf_check *scfcp = scfc_in;
  
  	if (likely(scfcp) && WARN_ONCE(smp_processor_id() != scfcp->scfc_cpu, "%s: Wanted CPU %d got CPU %d
  ", __func__, scfcp->scfc_cpu, smp_processor_id())) {

  		atomic_inc(&n_errs);

  	}
  	scf_handler(scfcp);

  }

  // Randomly do an smp_call_function*() invocation.

  static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_random_state *trsp)

  {

  	uintptr_t cpu;

  	int ret = 0;

  	struct scf_check *scfcp = NULL;

  	struct scf_selector *scfsp = scf_sel_rand(trsp);

  	if (use_cpus_read_lock)
  		cpus_read_lock();
  	else
  		preempt_disable();

  	if (scfsp->scfs_prim == SCF_PRIM_SINGLE || scfsp->scfs_wait) {

  		scfcp = kmalloc(sizeof(*scfcp), GFP_ATOMIC);

  		if (WARN_ON_ONCE(!scfcp)) {

  			atomic_inc(&n_alloc_errs);

  		} else {
  			scfcp->scfc_cpu = -1;
  			scfcp->scfc_wait = scfsp->scfs_wait;
  			scfcp->scfc_out = false;
  		}

  	}
  	switch (scfsp->scfs_prim) {
  	case SCF_PRIM_SINGLE:

  		cpu = torture_random(trsp) % nr_cpu_ids;
  		if (scfsp->scfs_wait)
  			scfp->n_single_wait++;
  		else
  			scfp->n_single++;

  		if (scfcp) {
  			scfcp->scfc_cpu = cpu;

  			barrier(); // Prevent race-reduction compiler optimizations.

  			scfcp->scfc_in = true;
  		}
  		ret = smp_call_function_single(cpu, scf_handler_1, (void *)scfcp, scfsp->scfs_wait);

  		if (ret) {
  			if (scfsp->scfs_wait)
  				scfp->n_single_wait_ofl++;
  			else
  				scfp->n_single_ofl++;

  			kfree(scfcp);

  			scfcp = NULL;

  		}
  		break;
  	case SCF_PRIM_MANY:
  		if (scfsp->scfs_wait)
  			scfp->n_many_wait++;
  		else
  			scfp->n_many++;

  		if (scfcp) {
  			barrier(); // Prevent race-reduction compiler optimizations.

  			scfcp->scfc_in = true;

  		}

  		smp_call_function_many(cpu_online_mask, scf_handler, scfcp, scfsp->scfs_wait);

  		break;
  	case SCF_PRIM_ALL:
  		if (scfsp->scfs_wait)
  			scfp->n_all_wait++;
  		else
  			scfp->n_all++;

  		if (scfcp) {
  			barrier(); // Prevent race-reduction compiler optimizations.

  			scfcp->scfc_in = true;

  		}

  		smp_call_function(scf_handler, scfcp, scfsp->scfs_wait);

  		break;

  	default:
  		WARN_ON_ONCE(1);
  		if (scfcp)
  			scfcp->scfc_out = true;

  	}

  	if (scfcp && scfsp->scfs_wait) {

  		if (WARN_ON_ONCE((num_online_cpus() > 1 || scfsp->scfs_prim == SCF_PRIM_SINGLE) &&
  				 !scfcp->scfc_out))

  			atomic_inc(&n_mb_out_errs); // Leak rather than trash!
  		else
  			kfree(scfcp);

  		barrier(); // Prevent race-reduction compiler optimizations.

  	}

  	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)
  {

  	int cpu;

  	DEFINE_TORTURE_RANDOM(rand);
  	struct scf_statistics *scfp = (struct scf_statistics *)arg;

  	bool was_offline = false;

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

  	cpu = scfp->cpu % nr_cpu_ids;
  	set_cpus_allowed_ptr(current, cpumask_of(cpu));

  	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 (cpu_is_offline(cpu) && !torture_must_stop()) {
  			schedule_timeout_interruptible(HZ / 5);
  			was_offline = true;
  		}
  		if (was_offline) {
  			set_cpus_allowed_ptr(current, cpumask_of(cpu));
  			was_offline = false;
  		}

  		cond_resched();

  	} 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_many=%d, weight_many_wait=%d, weight_all=%d, weight_all_wait=%d
  ", tag,
  		 verbose, holdoff, longwait, nthreads, onoff_holdoff, onoff_interval, shutdown, stat_interval, stutter_cpus, use_cpus_read_lock, weight_single, weight_single_wait, weight_many, weight_many_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;

  	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!

  	kfree(scf_stats_p);  // -After- the last stats print has completed!
  	scf_stats_p = NULL;

  	if (atomic_read(&n_errs) || atomic_read(&n_mb_in_errs) || atomic_read(&n_mb_out_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;

  	unsigned long weight_single1 = weight_single;
  	unsigned long weight_single_wait1 = weight_single_wait;
  	unsigned long weight_many1 = weight_many;
  	unsigned long weight_many_wait1 = weight_many_wait;
  	unsigned long weight_all1 = weight_all;
  	unsigned long weight_all_wait1 = weight_all_wait;

  
  	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_many == -1 && weight_many_wait == -1 &&

  	    weight_all == -1 && weight_all_wait == -1) {

  		weight_single1 = 2 * nr_cpu_ids;
  		weight_single_wait1 = 2 * nr_cpu_ids;
  		weight_many1 = 2;
  		weight_many_wait1 = 2;
  		weight_all1 = 1;
  		weight_all_wait1 = 1;

  	} else {
  		if (weight_single == -1)

  			weight_single1 = 0;

  		if (weight_single_wait == -1)

  			weight_single_wait1 = 0;
  		if (weight_many == -1)
  			weight_many1 = 0;
  		if (weight_many_wait == -1)
  			weight_many_wait1 = 0;

  		if (weight_all == -1)

  			weight_all1 = 0;

  		if (weight_all_wait == -1)

  			weight_all_wait1 = 0;

  	}

  	if (weight_single1 == 0 && weight_single_wait1 == 0 &&
  	    weight_many1 == 0 && weight_many_wait1 == 0 &&
  	    weight_all1 == 0 && weight_all_wait1 == 0) {
  		VERBOSE_SCFTORTOUT_ERRSTRING("all zero weights makes no sense");

  		firsterr = -EINVAL;
  		goto unwind;
  	}

  	scf_sel_add(weight_single1, SCF_PRIM_SINGLE, false);
  	scf_sel_add(weight_single_wait1, SCF_PRIM_SINGLE, true);
  	scf_sel_add(weight_many1, SCF_PRIM_MANY, false);
  	scf_sel_add(weight_many_wait1, SCF_PRIM_MANY, true);
  	scf_sel_add(weight_all1, SCF_PRIM_ALL, false);
  	scf_sel_add(weight_all_wait1, SCF_PRIM_ALL, true);
  	scf_sel_dump();

  
  	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
  ", 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);