summaryrefslogtreecommitdiff
path: root/kernel/scftorture.c
blob: 5cf40e438319144eb0761e65e66977411a155fb6 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
// 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, 5, "Number of jiffies to run/halt 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_resched, -1, "Testing weight for resched_cpu() operations.");
torture_param(int, weight_single, -1, "Testing weight for single-CPU no-wait operations.");
torture_param(int, weight_single_rpc, -1, "Testing weight for single-CPU RPC 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_resched;
	long long n_single;
	long long n_single_ofl;
	long long n_single_rpc;
	long long n_single_rpc_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_RESCHED	0
#define SCF_PRIM_SINGLE		1
#define SCF_PRIM_SINGLE_RPC	2
#define SCF_PRIM_MANY		3
#define SCF_PRIM_ALL		4
#define SCF_NPRIMS		8 // Need wait and no-wait versions of each,
				  //  except for SCF_PRIM_RESCHED and
				  //  SCF_PRIM_SINGLE_RPC.

static char *scf_prim_name[] = {
	"resched_cpu",
	"smp_call_function_single",
	"smp_call_function_single_rpc",
	"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;
	bool scfc_rpc;
	struct completion scfc_completion;
};

// 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);

extern void resched_cpu(int cpu); // An alternative IPI vector.

// 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_resched += scf_stats_p[i].n_resched;
		scfs.n_single += scf_stats_p[i].n_single;
		scfs.n_single_ofl += scf_stats_p[i].n_single_ofl;
		scfs.n_single_rpc += scf_stats_p[i].n_single_rpc;
		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 resched: %lld single: %lld/%lld single_ofl: %lld/%lld single_rpc: %lld single_rpc_ofl: %lld many: %lld/%lld all: %lld/%lld ",
		 SCFTORT_FLAG, bangstr, isdone ? "VER" : "ver", invoked_count, scfs.n_resched,
		 scfs.n_single, scfs.n_single_wait, scfs.n_single_ofl, scfs.n_single_wait_ofl,
		 scfs.n_single_rpc, scfs.n_single_rpc_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\n", 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)\n", __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);
		if (scfcp->scfc_rpc)
			complete(&scfcp->scfc_completion);
	} 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\n", __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;
			scfcp->scfc_rpc = false;
		}
	}
	switch (scfsp->scfs_prim) {
	case SCF_PRIM_RESCHED:
		if (IS_BUILTIN(CONFIG_SCF_TORTURE_TEST)) {
			cpu = torture_random(trsp) % nr_cpu_ids;
			scfp->n_resched++;
			resched_cpu(cpu);
		}
		break;
	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_SINGLE_RPC:
		if (!scfcp)
			break;
		cpu = torture_random(trsp) % nr_cpu_ids;
		scfp->n_single_rpc++;
		scfcp->scfc_cpu = cpu;
		scfcp->scfc_wait = true;
		init_completion(&scfcp->scfc_completion);
		scfcp->scfc_rpc = true;
		barrier(); // Prevent race-reduction compiler optimizations.
		scfcp->scfc_in = true;
		ret = smp_call_function_single(cpu, scf_handler_1, (void *)scfcp, 0);
		if (!ret) {
			if (use_cpus_read_lock)
				cpus_read_unlock();
			else
				preempt_enable();
			wait_for_completion(&scfcp->scfc_completion);
			if (use_cpus_read_lock)
				cpus_read_lock();
			else
				preempt_disable();
		} else {
			scfp->n_single_rpc_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)) {
			pr_warn("%s: Memory-ordering failure, scfs_prim: %d.\n", __func__, scfsp->scfs_prim);
			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;
	int curcpu;
	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;
	WARN_ON_ONCE(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, raw_smp_processor_id());

	// Make sure that the CPU is affinitized appropriately during testing.
	curcpu = raw_smp_processor_id();
	WARN_ONCE(curcpu != scfp->cpu % nr_cpu_ids,
		  "%s: Wanted CPU %d, running on %d, nr_cpu_ids = %d\n",
		  __func__, scfp->cpu, curcpu, nr_cpu_ids);

	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();
		stutter_wait("scftorture_invoker");
	} 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=%d use_cpus_read_lock=%d, weight_resched=%d, weight_single=%d, weight_single_rpc=%d, weight_single_wait=%d, weight_many=%d, weight_many_wait=%d, weight_all=%d, weight_all_wait=%d\n", tag,
		 verbose, holdoff, longwait, nthreads, onoff_holdoff, onoff_interval, shutdown, stat_interval, stutter, use_cpus_read_lock, weight_resched, weight_single, weight_single_rpc, 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_resched1 = weight_resched;
	unsigned long weight_single1 = weight_single;
	unsigned long weight_single_rpc1 = weight_single_rpc;
	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_resched == -1 &&
	    weight_single == -1 && weight_single_rpc == -1 && weight_single_wait == -1 &&
	    weight_many == -1 && weight_many_wait == -1 &&
	    weight_all == -1 && weight_all_wait == -1) {
		weight_resched1 = 2 * nr_cpu_ids;
		weight_single1 = 2 * nr_cpu_ids;
		weight_single_rpc1 = 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_resched == -1)
			weight_resched1 = 0;
		if (weight_single == -1)
			weight_single1 = 0;
		if (weight_single_rpc == -1)
			weight_single_rpc1 = 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_rpc1 == 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;
	}
	if (IS_BUILTIN(CONFIG_SCF_TORTURE_TEST))
		scf_sel_add(weight_resched1, SCF_PRIM_RESCHED, false);
	else if (weight_resched1)
		VERBOSE_SCFTORTOUT_ERRSTRING("built as module, weight_resched ignored");
	scf_sel_add(weight_single1, SCF_PRIM_SINGLE, false);
	scf_sel_add(weight_single_rpc1, SCF_PRIM_SINGLE_RPC, true);
	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;
	}
	if (stutter > 0) {
		firsterr = torture_stutter_init(stutter, stutter);
		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);