xref: /linux/kernel/scftorture.c (revision 0750b8fcf313845b21c71344b4bea8ad7d3cee84)
1 // SPDX-License-Identifier: GPL-2.0+
2 //
3 // Torture test for smp_call_function() and friends.
4 //
5 // Copyright (C) Facebook, 2020.
6 //
7 // Author: Paul E. McKenney <paulmck@kernel.org>
8 
9 #define pr_fmt(fmt) fmt
10 
11 #include <linux/atomic.h>
12 #include <linux/bitops.h>
13 #include <linux/completion.h>
14 #include <linux/cpu.h>
15 #include <linux/delay.h>
16 #include <linux/err.h>
17 #include <linux/init.h>
18 #include <linux/interrupt.h>
19 #include <linux/kthread.h>
20 #include <linux/kernel.h>
21 #include <linux/mm.h>
22 #include <linux/module.h>
23 #include <linux/moduleparam.h>
24 #include <linux/notifier.h>
25 #include <linux/percpu.h>
26 #include <linux/rcupdate.h>
27 #include <linux/rcupdate_trace.h>
28 #include <linux/reboot.h>
29 #include <linux/sched.h>
30 #include <linux/spinlock.h>
31 #include <linux/smp.h>
32 #include <linux/stat.h>
33 #include <linux/srcu.h>
34 #include <linux/slab.h>
35 #include <linux/torture.h>
36 #include <linux/types.h>
37 
38 #define SCFTORT_STRING "scftorture"
39 #define SCFTORT_FLAG SCFTORT_STRING ": "
40 
41 #define VERBOSE_SCFTORTOUT(s, x...) \
42 	do { if (verbose) pr_alert(SCFTORT_FLAG s "\n", ## x); } while (0)
43 
44 #define SCFTORTOUT_ERRSTRING(s, x...) pr_alert(SCFTORT_FLAG "!!! " s "\n", ## x)
45 
46 MODULE_LICENSE("GPL");
47 MODULE_AUTHOR("Paul E. McKenney <paulmck@kernel.org>");
48 
49 // Wait until there are multiple CPUs before starting test.
50 torture_param(int, holdoff, IS_BUILTIN(CONFIG_SCF_TORTURE_TEST) ? 10 : 0,
51 	      "Holdoff time before test start (s)");
52 torture_param(int, longwait, 0, "Include ridiculously long waits? (seconds)");
53 torture_param(int, nthreads, -1, "# threads, defaults to -1 for all CPUs.");
54 torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
55 torture_param(int, onoff_interval, 0, "Time between CPU hotplugs (s), 0=disable");
56 torture_param(int, shutdown_secs, 0, "Shutdown time (ms), <= zero to disable.");
57 torture_param(int, stat_interval, 60, "Number of seconds between stats printk()s.");
58 torture_param(int, stutter, 5, "Number of jiffies to run/halt test, 0=disable");
59 torture_param(bool, use_cpus_read_lock, 0, "Use cpus_read_lock() to exclude CPU hotplug.");
60 torture_param(int, verbose, 0, "Enable verbose debugging printk()s");
61 torture_param(int, weight_resched, -1, "Testing weight for resched_cpu() operations.");
62 torture_param(int, weight_single, -1, "Testing weight for single-CPU no-wait operations.");
63 torture_param(int, weight_single_rpc, -1, "Testing weight for single-CPU RPC operations.");
64 torture_param(int, weight_single_wait, -1, "Testing weight for single-CPU operations.");
65 torture_param(int, weight_many, -1, "Testing weight for multi-CPU no-wait operations.");
66 torture_param(int, weight_many_wait, -1, "Testing weight for multi-CPU operations.");
67 torture_param(int, weight_all, -1, "Testing weight for all-CPU no-wait operations.");
68 torture_param(int, weight_all_wait, -1, "Testing weight for all-CPU operations.");
69 
70 char *torture_type = "";
71 
72 #ifdef MODULE
73 # define SCFTORT_SHUTDOWN 0
74 #else
75 # define SCFTORT_SHUTDOWN 1
76 #endif
77 
78 torture_param(bool, shutdown, SCFTORT_SHUTDOWN, "Shutdown at end of torture test.");
79 
80 struct scf_statistics {
81 	struct task_struct *task;
82 	int cpu;
83 	long long n_resched;
84 	long long n_single;
85 	long long n_single_ofl;
86 	long long n_single_rpc;
87 	long long n_single_rpc_ofl;
88 	long long n_single_wait;
89 	long long n_single_wait_ofl;
90 	long long n_many;
91 	long long n_many_wait;
92 	long long n_all;
93 	long long n_all_wait;
94 };
95 
96 static struct scf_statistics *scf_stats_p;
97 static struct task_struct *scf_torture_stats_task;
98 static DEFINE_PER_CPU(long long, scf_invoked_count);
99 
100 // Data for random primitive selection
101 #define SCF_PRIM_RESCHED	0
102 #define SCF_PRIM_SINGLE		1
103 #define SCF_PRIM_SINGLE_RPC	2
104 #define SCF_PRIM_MANY		3
105 #define SCF_PRIM_ALL		4
106 #define SCF_NPRIMS		8 // Need wait and no-wait versions of each,
107 				  //  except for SCF_PRIM_RESCHED and
108 				  //  SCF_PRIM_SINGLE_RPC.
109 
110 static char *scf_prim_name[] = {
111 	"resched_cpu",
112 	"smp_call_function_single",
113 	"smp_call_function_single_rpc",
114 	"smp_call_function_many",
115 	"smp_call_function",
116 };
117 
118 struct scf_selector {
119 	unsigned long scfs_weight;
120 	int scfs_prim;
121 	bool scfs_wait;
122 };
123 static struct scf_selector scf_sel_array[SCF_NPRIMS];
124 static int scf_sel_array_len;
125 static unsigned long scf_sel_totweight;
126 
127 // Communicate between caller and handler.
128 struct scf_check {
129 	bool scfc_in;
130 	bool scfc_out;
131 	int scfc_cpu; // -1 for not _single().
132 	bool scfc_wait;
133 	bool scfc_rpc;
134 	struct completion scfc_completion;
135 };
136 
137 // Use to wait for all threads to start.
138 static atomic_t n_started;
139 static atomic_t n_errs;
140 static atomic_t n_mb_in_errs;
141 static atomic_t n_mb_out_errs;
142 static atomic_t n_alloc_errs;
143 static bool scfdone;
144 static char *bangstr = "";
145 
146 static DEFINE_TORTURE_RANDOM_PERCPU(scf_torture_rand);
147 
148 extern void resched_cpu(int cpu); // An alternative IPI vector.
149 
150 // Print torture statistics.  Caller must ensure serialization.
151 static void scf_torture_stats_print(void)
152 {
153 	int cpu;
154 	int i;
155 	long long invoked_count = 0;
156 	bool isdone = READ_ONCE(scfdone);
157 	struct scf_statistics scfs = {};
158 
159 	for_each_possible_cpu(cpu)
160 		invoked_count += data_race(per_cpu(scf_invoked_count, cpu));
161 	for (i = 0; i < nthreads; i++) {
162 		scfs.n_resched += scf_stats_p[i].n_resched;
163 		scfs.n_single += scf_stats_p[i].n_single;
164 		scfs.n_single_ofl += scf_stats_p[i].n_single_ofl;
165 		scfs.n_single_rpc += scf_stats_p[i].n_single_rpc;
166 		scfs.n_single_wait += scf_stats_p[i].n_single_wait;
167 		scfs.n_single_wait_ofl += scf_stats_p[i].n_single_wait_ofl;
168 		scfs.n_many += scf_stats_p[i].n_many;
169 		scfs.n_many_wait += scf_stats_p[i].n_many_wait;
170 		scfs.n_all += scf_stats_p[i].n_all;
171 		scfs.n_all_wait += scf_stats_p[i].n_all_wait;
172 	}
173 	if (atomic_read(&n_errs) || atomic_read(&n_mb_in_errs) ||
174 	    atomic_read(&n_mb_out_errs) || atomic_read(&n_alloc_errs))
175 		bangstr = "!!! ";
176 	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 ",
177 		 SCFTORT_FLAG, bangstr, isdone ? "VER" : "ver", invoked_count, scfs.n_resched,
178 		 scfs.n_single, scfs.n_single_wait, scfs.n_single_ofl, scfs.n_single_wait_ofl,
179 		 scfs.n_single_rpc, scfs.n_single_rpc_ofl,
180 		 scfs.n_many, scfs.n_many_wait, scfs.n_all, scfs.n_all_wait);
181 	torture_onoff_stats();
182 	pr_cont("ste: %d stnmie: %d stnmoe: %d staf: %d\n", atomic_read(&n_errs),
183 		atomic_read(&n_mb_in_errs), atomic_read(&n_mb_out_errs),
184 		atomic_read(&n_alloc_errs));
185 }
186 
187 // Periodically prints torture statistics, if periodic statistics printing
188 // was specified via the stat_interval module parameter.
189 static int
190 scf_torture_stats(void *arg)
191 {
192 	VERBOSE_TOROUT_STRING("scf_torture_stats task started");
193 	do {
194 		schedule_timeout_interruptible(stat_interval * HZ);
195 		scf_torture_stats_print();
196 		torture_shutdown_absorb("scf_torture_stats");
197 	} while (!torture_must_stop());
198 	torture_kthread_stopping("scf_torture_stats");
199 	return 0;
200 }
201 
202 // Add a primitive to the scf_sel_array[].
203 static void scf_sel_add(unsigned long weight, int prim, bool wait)
204 {
205 	struct scf_selector *scfsp = &scf_sel_array[scf_sel_array_len];
206 
207 	// If no weight, if array would overflow, if computing three-place
208 	// percentages would overflow, or if the scf_prim_name[] array would
209 	// overflow, don't bother.  In the last three two cases, complain.
210 	if (!weight ||
211 	    WARN_ON_ONCE(scf_sel_array_len >= ARRAY_SIZE(scf_sel_array)) ||
212 	    WARN_ON_ONCE(0 - 100000 * weight <= 100000 * scf_sel_totweight) ||
213 	    WARN_ON_ONCE(prim >= ARRAY_SIZE(scf_prim_name)))
214 		return;
215 	scf_sel_totweight += weight;
216 	scfsp->scfs_weight = scf_sel_totweight;
217 	scfsp->scfs_prim = prim;
218 	scfsp->scfs_wait = wait;
219 	scf_sel_array_len++;
220 }
221 
222 // Dump out weighting percentages for scf_prim_name[] array.
223 static void scf_sel_dump(void)
224 {
225 	int i;
226 	unsigned long oldw = 0;
227 	struct scf_selector *scfsp;
228 	unsigned long w;
229 
230 	for (i = 0; i < scf_sel_array_len; i++) {
231 		scfsp = &scf_sel_array[i];
232 		w = (scfsp->scfs_weight - oldw) * 100000 / scf_sel_totweight;
233 		pr_info("%s: %3lu.%03lu %s(%s)\n", __func__, w / 1000, w % 1000,
234 			scf_prim_name[scfsp->scfs_prim],
235 			scfsp->scfs_wait ? "wait" : "nowait");
236 		oldw = scfsp->scfs_weight;
237 	}
238 }
239 
240 // Randomly pick a primitive and wait/nowait, based on weightings.
241 static struct scf_selector *scf_sel_rand(struct torture_random_state *trsp)
242 {
243 	int i;
244 	unsigned long w = torture_random(trsp) % (scf_sel_totweight + 1);
245 
246 	for (i = 0; i < scf_sel_array_len; i++)
247 		if (scf_sel_array[i].scfs_weight >= w)
248 			return &scf_sel_array[i];
249 	WARN_ON_ONCE(1);
250 	return &scf_sel_array[0];
251 }
252 
253 // Update statistics and occasionally burn up mass quantities of CPU time,
254 // if told to do so via scftorture.longwait.  Otherwise, occasionally burn
255 // a little bit.
256 static void scf_handler(void *scfc_in)
257 {
258 	int i;
259 	int j;
260 	unsigned long r = torture_random(this_cpu_ptr(&scf_torture_rand));
261 	struct scf_check *scfcp = scfc_in;
262 
263 	if (likely(scfcp)) {
264 		WRITE_ONCE(scfcp->scfc_out, false); // For multiple receivers.
265 		if (WARN_ON_ONCE(unlikely(!READ_ONCE(scfcp->scfc_in))))
266 			atomic_inc(&n_mb_in_errs);
267 	}
268 	this_cpu_inc(scf_invoked_count);
269 	if (longwait <= 0) {
270 		if (!(r & 0xffc0))
271 			udelay(r & 0x3f);
272 		goto out;
273 	}
274 	if (r & 0xfff)
275 		goto out;
276 	r = (r >> 12);
277 	if (longwait <= 0) {
278 		udelay((r & 0xff) + 1);
279 		goto out;
280 	}
281 	r = r % longwait + 1;
282 	for (i = 0; i < r; i++) {
283 		for (j = 0; j < 1000; j++) {
284 			udelay(1000);
285 			cpu_relax();
286 		}
287 	}
288 out:
289 	if (unlikely(!scfcp))
290 		return;
291 	if (scfcp->scfc_wait) {
292 		WRITE_ONCE(scfcp->scfc_out, true);
293 		if (scfcp->scfc_rpc)
294 			complete(&scfcp->scfc_completion);
295 	} else {
296 		kfree(scfcp);
297 	}
298 }
299 
300 // As above, but check for correct CPU.
301 static void scf_handler_1(void *scfc_in)
302 {
303 	struct scf_check *scfcp = scfc_in;
304 
305 	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())) {
306 		atomic_inc(&n_errs);
307 	}
308 	scf_handler(scfcp);
309 }
310 
311 // Randomly do an smp_call_function*() invocation.
312 static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_random_state *trsp)
313 {
314 	uintptr_t cpu;
315 	int ret = 0;
316 	struct scf_check *scfcp = NULL;
317 	struct scf_selector *scfsp = scf_sel_rand(trsp);
318 
319 	if (use_cpus_read_lock)
320 		cpus_read_lock();
321 	else
322 		preempt_disable();
323 	if (scfsp->scfs_prim == SCF_PRIM_SINGLE || scfsp->scfs_wait) {
324 		scfcp = kmalloc(sizeof(*scfcp), GFP_ATOMIC);
325 		if (WARN_ON_ONCE(!scfcp)) {
326 			atomic_inc(&n_alloc_errs);
327 		} else {
328 			scfcp->scfc_cpu = -1;
329 			scfcp->scfc_wait = scfsp->scfs_wait;
330 			scfcp->scfc_out = false;
331 			scfcp->scfc_rpc = false;
332 		}
333 	}
334 	switch (scfsp->scfs_prim) {
335 	case SCF_PRIM_RESCHED:
336 		if (IS_BUILTIN(CONFIG_SCF_TORTURE_TEST)) {
337 			cpu = torture_random(trsp) % nr_cpu_ids;
338 			scfp->n_resched++;
339 			resched_cpu(cpu);
340 			this_cpu_inc(scf_invoked_count);
341 		}
342 		break;
343 	case SCF_PRIM_SINGLE:
344 		cpu = torture_random(trsp) % nr_cpu_ids;
345 		if (scfsp->scfs_wait)
346 			scfp->n_single_wait++;
347 		else
348 			scfp->n_single++;
349 		if (scfcp) {
350 			scfcp->scfc_cpu = cpu;
351 			barrier(); // Prevent race-reduction compiler optimizations.
352 			scfcp->scfc_in = true;
353 		}
354 		ret = smp_call_function_single(cpu, scf_handler_1, (void *)scfcp, scfsp->scfs_wait);
355 		if (ret) {
356 			if (scfsp->scfs_wait)
357 				scfp->n_single_wait_ofl++;
358 			else
359 				scfp->n_single_ofl++;
360 			kfree(scfcp);
361 			scfcp = NULL;
362 		}
363 		break;
364 	case SCF_PRIM_SINGLE_RPC:
365 		if (!scfcp)
366 			break;
367 		cpu = torture_random(trsp) % nr_cpu_ids;
368 		scfp->n_single_rpc++;
369 		scfcp->scfc_cpu = cpu;
370 		scfcp->scfc_wait = true;
371 		init_completion(&scfcp->scfc_completion);
372 		scfcp->scfc_rpc = true;
373 		barrier(); // Prevent race-reduction compiler optimizations.
374 		scfcp->scfc_in = true;
375 		ret = smp_call_function_single(cpu, scf_handler_1, (void *)scfcp, 0);
376 		if (!ret) {
377 			if (use_cpus_read_lock)
378 				cpus_read_unlock();
379 			else
380 				preempt_enable();
381 			wait_for_completion(&scfcp->scfc_completion);
382 			if (use_cpus_read_lock)
383 				cpus_read_lock();
384 			else
385 				preempt_disable();
386 		} else {
387 			scfp->n_single_rpc_ofl++;
388 			kfree(scfcp);
389 			scfcp = NULL;
390 		}
391 		break;
392 	case SCF_PRIM_MANY:
393 		if (scfsp->scfs_wait)
394 			scfp->n_many_wait++;
395 		else
396 			scfp->n_many++;
397 		if (scfcp) {
398 			barrier(); // Prevent race-reduction compiler optimizations.
399 			scfcp->scfc_in = true;
400 		}
401 		smp_call_function_many(cpu_online_mask, scf_handler, scfcp, scfsp->scfs_wait);
402 		break;
403 	case SCF_PRIM_ALL:
404 		if (scfsp->scfs_wait)
405 			scfp->n_all_wait++;
406 		else
407 			scfp->n_all++;
408 		if (scfcp) {
409 			barrier(); // Prevent race-reduction compiler optimizations.
410 			scfcp->scfc_in = true;
411 		}
412 		smp_call_function(scf_handler, scfcp, scfsp->scfs_wait);
413 		break;
414 	default:
415 		WARN_ON_ONCE(1);
416 		if (scfcp)
417 			scfcp->scfc_out = true;
418 	}
419 	if (scfcp && scfsp->scfs_wait) {
420 		if (WARN_ON_ONCE((num_online_cpus() > 1 || scfsp->scfs_prim == SCF_PRIM_SINGLE) &&
421 				 !scfcp->scfc_out)) {
422 			pr_warn("%s: Memory-ordering failure, scfs_prim: %d.\n", __func__, scfsp->scfs_prim);
423 			atomic_inc(&n_mb_out_errs); // Leak rather than trash!
424 		} else {
425 			kfree(scfcp);
426 		}
427 		barrier(); // Prevent race-reduction compiler optimizations.
428 	}
429 	if (use_cpus_read_lock)
430 		cpus_read_unlock();
431 	else
432 		preempt_enable();
433 	if (!(torture_random(trsp) & 0xfff))
434 		schedule_timeout_uninterruptible(1);
435 }
436 
437 // SCF test kthread.  Repeatedly does calls to members of the
438 // smp_call_function() family of functions.
439 static int scftorture_invoker(void *arg)
440 {
441 	int cpu;
442 	int curcpu;
443 	DEFINE_TORTURE_RANDOM(rand);
444 	struct scf_statistics *scfp = (struct scf_statistics *)arg;
445 	bool was_offline = false;
446 
447 	VERBOSE_SCFTORTOUT("scftorture_invoker %d: task started", scfp->cpu);
448 	cpu = scfp->cpu % nr_cpu_ids;
449 	WARN_ON_ONCE(set_cpus_allowed_ptr(current, cpumask_of(cpu)));
450 	set_user_nice(current, MAX_NICE);
451 	if (holdoff)
452 		schedule_timeout_interruptible(holdoff * HZ);
453 
454 	VERBOSE_SCFTORTOUT("scftorture_invoker %d: Waiting for all SCF torturers from cpu %d", scfp->cpu, raw_smp_processor_id());
455 
456 	// Make sure that the CPU is affinitized appropriately during testing.
457 	curcpu = raw_smp_processor_id();
458 	WARN_ONCE(curcpu != scfp->cpu % nr_cpu_ids,
459 		  "%s: Wanted CPU %d, running on %d, nr_cpu_ids = %d\n",
460 		  __func__, scfp->cpu, curcpu, nr_cpu_ids);
461 
462 	if (!atomic_dec_return(&n_started))
463 		while (atomic_read_acquire(&n_started)) {
464 			if (torture_must_stop()) {
465 				VERBOSE_SCFTORTOUT("scftorture_invoker %d ended before starting", scfp->cpu);
466 				goto end;
467 			}
468 			schedule_timeout_uninterruptible(1);
469 		}
470 
471 	VERBOSE_SCFTORTOUT("scftorture_invoker %d started", scfp->cpu);
472 
473 	do {
474 		scftorture_invoke_one(scfp, &rand);
475 		while (cpu_is_offline(cpu) && !torture_must_stop()) {
476 			schedule_timeout_interruptible(HZ / 5);
477 			was_offline = true;
478 		}
479 		if (was_offline) {
480 			set_cpus_allowed_ptr(current, cpumask_of(cpu));
481 			was_offline = false;
482 		}
483 		cond_resched();
484 		stutter_wait("scftorture_invoker");
485 	} while (!torture_must_stop());
486 
487 	VERBOSE_SCFTORTOUT("scftorture_invoker %d ended", scfp->cpu);
488 end:
489 	torture_kthread_stopping("scftorture_invoker");
490 	return 0;
491 }
492 
493 static void
494 scftorture_print_module_parms(const char *tag)
495 {
496 	pr_alert(SCFTORT_FLAG
497 		 "--- %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,
498 		 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);
499 }
500 
501 static void scf_cleanup_handler(void *unused)
502 {
503 }
504 
505 static void scf_torture_cleanup(void)
506 {
507 	int i;
508 
509 	if (torture_cleanup_begin())
510 		return;
511 
512 	WRITE_ONCE(scfdone, true);
513 	if (nthreads && scf_stats_p)
514 		for (i = 0; i < nthreads; i++)
515 			torture_stop_kthread("scftorture_invoker", scf_stats_p[i].task);
516 	else
517 		goto end;
518 	smp_call_function(scf_cleanup_handler, NULL, 0);
519 	torture_stop_kthread(scf_torture_stats, scf_torture_stats_task);
520 	scf_torture_stats_print();  // -After- the stats thread is stopped!
521 	kfree(scf_stats_p);  // -After- the last stats print has completed!
522 	scf_stats_p = NULL;
523 
524 	if (atomic_read(&n_errs) || atomic_read(&n_mb_in_errs) || atomic_read(&n_mb_out_errs))
525 		scftorture_print_module_parms("End of test: FAILURE");
526 	else if (torture_onoff_failures())
527 		scftorture_print_module_parms("End of test: LOCK_HOTPLUG");
528 	else
529 		scftorture_print_module_parms("End of test: SUCCESS");
530 
531 end:
532 	torture_cleanup_end();
533 }
534 
535 static int __init scf_torture_init(void)
536 {
537 	long i;
538 	int firsterr = 0;
539 	unsigned long weight_resched1 = weight_resched;
540 	unsigned long weight_single1 = weight_single;
541 	unsigned long weight_single_rpc1 = weight_single_rpc;
542 	unsigned long weight_single_wait1 = weight_single_wait;
543 	unsigned long weight_many1 = weight_many;
544 	unsigned long weight_many_wait1 = weight_many_wait;
545 	unsigned long weight_all1 = weight_all;
546 	unsigned long weight_all_wait1 = weight_all_wait;
547 
548 	if (!torture_init_begin(SCFTORT_STRING, verbose))
549 		return -EBUSY;
550 
551 	scftorture_print_module_parms("Start of test");
552 
553 	if (weight_resched <= 0 &&
554 	    weight_single <= 0 && weight_single_rpc <= 0 && weight_single_wait <= 0 &&
555 	    weight_many <= 0 && weight_many_wait <= 0 &&
556 	    weight_all <= 0 && weight_all_wait <= 0) {
557 		weight_resched1 = weight_resched == 0 ? 0 : 2 * nr_cpu_ids;
558 		weight_single1 = weight_single == 0 ? 0 : 2 * nr_cpu_ids;
559 		weight_single_rpc1 = weight_single_rpc == 0 ? 0 : 2 * nr_cpu_ids;
560 		weight_single_wait1 = weight_single_wait == 0 ? 0 : 2 * nr_cpu_ids;
561 		weight_many1 = weight_many == 0 ? 0 : 2;
562 		weight_many_wait1 = weight_many_wait == 0 ? 0 : 2;
563 		weight_all1 = weight_all == 0 ? 0 : 1;
564 		weight_all_wait1 = weight_all_wait == 0 ? 0 : 1;
565 	} else {
566 		if (weight_resched == -1)
567 			weight_resched1 = 0;
568 		if (weight_single == -1)
569 			weight_single1 = 0;
570 		if (weight_single_rpc == -1)
571 			weight_single_rpc1 = 0;
572 		if (weight_single_wait == -1)
573 			weight_single_wait1 = 0;
574 		if (weight_many == -1)
575 			weight_many1 = 0;
576 		if (weight_many_wait == -1)
577 			weight_many_wait1 = 0;
578 		if (weight_all == -1)
579 			weight_all1 = 0;
580 		if (weight_all_wait == -1)
581 			weight_all_wait1 = 0;
582 	}
583 	if (weight_resched1 == 0 && weight_single1 == 0 && weight_single_rpc1 == 0 &&
584 	    weight_single_wait1 == 0 && weight_many1 == 0 && weight_many_wait1 == 0 &&
585 	    weight_all1 == 0 && weight_all_wait1 == 0) {
586 		SCFTORTOUT_ERRSTRING("all zero weights makes no sense");
587 		firsterr = -EINVAL;
588 		goto unwind;
589 	}
590 	if (IS_BUILTIN(CONFIG_SCF_TORTURE_TEST))
591 		scf_sel_add(weight_resched1, SCF_PRIM_RESCHED, false);
592 	else if (weight_resched1)
593 		SCFTORTOUT_ERRSTRING("built as module, weight_resched ignored");
594 	scf_sel_add(weight_single1, SCF_PRIM_SINGLE, false);
595 	scf_sel_add(weight_single_rpc1, SCF_PRIM_SINGLE_RPC, true);
596 	scf_sel_add(weight_single_wait1, SCF_PRIM_SINGLE, true);
597 	scf_sel_add(weight_many1, SCF_PRIM_MANY, false);
598 	scf_sel_add(weight_many_wait1, SCF_PRIM_MANY, true);
599 	scf_sel_add(weight_all1, SCF_PRIM_ALL, false);
600 	scf_sel_add(weight_all_wait1, SCF_PRIM_ALL, true);
601 	scf_sel_dump();
602 
603 	if (onoff_interval > 0) {
604 		firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval, NULL);
605 		if (torture_init_error(firsterr))
606 			goto unwind;
607 	}
608 	if (shutdown_secs > 0) {
609 		firsterr = torture_shutdown_init(shutdown_secs, scf_torture_cleanup);
610 		if (torture_init_error(firsterr))
611 			goto unwind;
612 	}
613 	if (stutter > 0) {
614 		firsterr = torture_stutter_init(stutter, stutter);
615 		if (torture_init_error(firsterr))
616 			goto unwind;
617 	}
618 
619 	// Worker tasks invoking smp_call_function().
620 	if (nthreads < 0)
621 		nthreads = num_online_cpus();
622 	scf_stats_p = kcalloc(nthreads, sizeof(scf_stats_p[0]), GFP_KERNEL);
623 	if (!scf_stats_p) {
624 		SCFTORTOUT_ERRSTRING("out of memory");
625 		firsterr = -ENOMEM;
626 		goto unwind;
627 	}
628 
629 	VERBOSE_SCFTORTOUT("Starting %d smp_call_function() threads", nthreads);
630 
631 	atomic_set(&n_started, nthreads);
632 	for (i = 0; i < nthreads; i++) {
633 		scf_stats_p[i].cpu = i;
634 		firsterr = torture_create_kthread(scftorture_invoker, (void *)&scf_stats_p[i],
635 						  scf_stats_p[i].task);
636 		if (torture_init_error(firsterr))
637 			goto unwind;
638 	}
639 	if (stat_interval > 0) {
640 		firsterr = torture_create_kthread(scf_torture_stats, NULL, scf_torture_stats_task);
641 		if (torture_init_error(firsterr))
642 			goto unwind;
643 	}
644 
645 	torture_init_end();
646 	return 0;
647 
648 unwind:
649 	torture_init_end();
650 	scf_torture_cleanup();
651 	if (shutdown_secs) {
652 		WARN_ON(!IS_MODULE(CONFIG_SCF_TORTURE_TEST));
653 		kernel_power_off();
654 	}
655 	return firsterr;
656 }
657 
658 module_init(scf_torture_init);
659 module_exit(scf_torture_cleanup);
660