xref: /linux/kernel/scftorture.c (revision 2697b79a469b68e3ad3640f55284359c1396278d)
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) ||
175 	    (!IS_ENABLED(CONFIG_KASAN) && atomic_read(&n_alloc_errs)))
176 		bangstr = "!!! ";
177 	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 ",
178 		 SCFTORT_FLAG, bangstr, isdone ? "VER" : "ver", invoked_count, scfs.n_resched,
179 		 scfs.n_single, scfs.n_single_wait, scfs.n_single_ofl, scfs.n_single_wait_ofl,
180 		 scfs.n_single_rpc, scfs.n_single_rpc_ofl,
181 		 scfs.n_many, scfs.n_many_wait, scfs.n_all, scfs.n_all_wait);
182 	torture_onoff_stats();
183 	pr_cont("ste: %d stnmie: %d stnmoe: %d staf: %d\n", atomic_read(&n_errs),
184 		atomic_read(&n_mb_in_errs), atomic_read(&n_mb_out_errs),
185 		atomic_read(&n_alloc_errs));
186 }
187 
188 // Periodically prints torture statistics, if periodic statistics printing
189 // was specified via the stat_interval module parameter.
190 static int
191 scf_torture_stats(void *arg)
192 {
193 	VERBOSE_TOROUT_STRING("scf_torture_stats task started");
194 	do {
195 		schedule_timeout_interruptible(stat_interval * HZ);
196 		scf_torture_stats_print();
197 		torture_shutdown_absorb("scf_torture_stats");
198 	} while (!torture_must_stop());
199 	torture_kthread_stopping("scf_torture_stats");
200 	return 0;
201 }
202 
203 // Add a primitive to the scf_sel_array[].
204 static void scf_sel_add(unsigned long weight, int prim, bool wait)
205 {
206 	struct scf_selector *scfsp = &scf_sel_array[scf_sel_array_len];
207 
208 	// If no weight, if array would overflow, if computing three-place
209 	// percentages would overflow, or if the scf_prim_name[] array would
210 	// overflow, don't bother.  In the last three two cases, complain.
211 	if (!weight ||
212 	    WARN_ON_ONCE(scf_sel_array_len >= ARRAY_SIZE(scf_sel_array)) ||
213 	    WARN_ON_ONCE(0 - 100000 * weight <= 100000 * scf_sel_totweight) ||
214 	    WARN_ON_ONCE(prim >= ARRAY_SIZE(scf_prim_name)))
215 		return;
216 	scf_sel_totweight += weight;
217 	scfsp->scfs_weight = scf_sel_totweight;
218 	scfsp->scfs_prim = prim;
219 	scfsp->scfs_wait = wait;
220 	scf_sel_array_len++;
221 }
222 
223 // Dump out weighting percentages for scf_prim_name[] array.
224 static void scf_sel_dump(void)
225 {
226 	int i;
227 	unsigned long oldw = 0;
228 	struct scf_selector *scfsp;
229 	unsigned long w;
230 
231 	for (i = 0; i < scf_sel_array_len; i++) {
232 		scfsp = &scf_sel_array[i];
233 		w = (scfsp->scfs_weight - oldw) * 100000 / scf_sel_totweight;
234 		pr_info("%s: %3lu.%03lu %s(%s)\n", __func__, w / 1000, w % 1000,
235 			scf_prim_name[scfsp->scfs_prim],
236 			scfsp->scfs_wait ? "wait" : "nowait");
237 		oldw = scfsp->scfs_weight;
238 	}
239 }
240 
241 // Randomly pick a primitive and wait/nowait, based on weightings.
242 static struct scf_selector *scf_sel_rand(struct torture_random_state *trsp)
243 {
244 	int i;
245 	unsigned long w = torture_random(trsp) % (scf_sel_totweight + 1);
246 
247 	for (i = 0; i < scf_sel_array_len; i++)
248 		if (scf_sel_array[i].scfs_weight >= w)
249 			return &scf_sel_array[i];
250 	WARN_ON_ONCE(1);
251 	return &scf_sel_array[0];
252 }
253 
254 // Update statistics and occasionally burn up mass quantities of CPU time,
255 // if told to do so via scftorture.longwait.  Otherwise, occasionally burn
256 // a little bit.
257 static void scf_handler(void *scfc_in)
258 {
259 	int i;
260 	int j;
261 	unsigned long r = torture_random(this_cpu_ptr(&scf_torture_rand));
262 	struct scf_check *scfcp = scfc_in;
263 
264 	if (likely(scfcp)) {
265 		WRITE_ONCE(scfcp->scfc_out, false); // For multiple receivers.
266 		if (WARN_ON_ONCE(unlikely(!READ_ONCE(scfcp->scfc_in))))
267 			atomic_inc(&n_mb_in_errs);
268 	}
269 	this_cpu_inc(scf_invoked_count);
270 	if (longwait <= 0) {
271 		if (!(r & 0xffc0)) {
272 			udelay(r & 0x3f);
273 			goto out;
274 		}
275 	}
276 	if (r & 0xfff)
277 		goto out;
278 	r = (r >> 12);
279 	if (longwait <= 0) {
280 		udelay((r & 0xff) + 1);
281 		goto out;
282 	}
283 	r = r % longwait + 1;
284 	for (i = 0; i < r; i++) {
285 		for (j = 0; j < 1000; j++) {
286 			udelay(1000);
287 			cpu_relax();
288 		}
289 	}
290 out:
291 	if (unlikely(!scfcp))
292 		return;
293 	if (scfcp->scfc_wait) {
294 		WRITE_ONCE(scfcp->scfc_out, true);
295 		if (scfcp->scfc_rpc)
296 			complete(&scfcp->scfc_completion);
297 	} else {
298 		kfree(scfcp);
299 	}
300 }
301 
302 // As above, but check for correct CPU.
303 static void scf_handler_1(void *scfc_in)
304 {
305 	struct scf_check *scfcp = scfc_in;
306 
307 	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())) {
308 		atomic_inc(&n_errs);
309 	}
310 	scf_handler(scfcp);
311 }
312 
313 // Randomly do an smp_call_function*() invocation.
314 static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_random_state *trsp)
315 {
316 	bool allocfail = false;
317 	uintptr_t cpu;
318 	int ret = 0;
319 	struct scf_check *scfcp = NULL;
320 	struct scf_selector *scfsp = scf_sel_rand(trsp);
321 
322 	if (use_cpus_read_lock)
323 		cpus_read_lock();
324 	else
325 		preempt_disable();
326 	if (scfsp->scfs_prim == SCF_PRIM_SINGLE || scfsp->scfs_wait) {
327 		scfcp = kmalloc(sizeof(*scfcp), GFP_ATOMIC);
328 		if (!scfcp) {
329 			WARN_ON_ONCE(!IS_ENABLED(CONFIG_KASAN));
330 			atomic_inc(&n_alloc_errs);
331 			allocfail = true;
332 		} else {
333 			scfcp->scfc_cpu = -1;
334 			scfcp->scfc_wait = scfsp->scfs_wait;
335 			scfcp->scfc_out = false;
336 			scfcp->scfc_rpc = false;
337 		}
338 	}
339 	switch (scfsp->scfs_prim) {
340 	case SCF_PRIM_RESCHED:
341 		if (IS_BUILTIN(CONFIG_SCF_TORTURE_TEST)) {
342 			cpu = torture_random(trsp) % nr_cpu_ids;
343 			scfp->n_resched++;
344 			resched_cpu(cpu);
345 			this_cpu_inc(scf_invoked_count);
346 		}
347 		break;
348 	case SCF_PRIM_SINGLE:
349 		cpu = torture_random(trsp) % nr_cpu_ids;
350 		if (scfsp->scfs_wait)
351 			scfp->n_single_wait++;
352 		else
353 			scfp->n_single++;
354 		if (scfcp) {
355 			scfcp->scfc_cpu = cpu;
356 			barrier(); // Prevent race-reduction compiler optimizations.
357 			scfcp->scfc_in = true;
358 		}
359 		ret = smp_call_function_single(cpu, scf_handler_1, (void *)scfcp, scfsp->scfs_wait);
360 		if (ret) {
361 			if (scfsp->scfs_wait)
362 				scfp->n_single_wait_ofl++;
363 			else
364 				scfp->n_single_ofl++;
365 			kfree(scfcp);
366 			scfcp = NULL;
367 		}
368 		break;
369 	case SCF_PRIM_SINGLE_RPC:
370 		if (!scfcp)
371 			break;
372 		cpu = torture_random(trsp) % nr_cpu_ids;
373 		scfp->n_single_rpc++;
374 		scfcp->scfc_cpu = cpu;
375 		scfcp->scfc_wait = true;
376 		init_completion(&scfcp->scfc_completion);
377 		scfcp->scfc_rpc = true;
378 		barrier(); // Prevent race-reduction compiler optimizations.
379 		scfcp->scfc_in = true;
380 		ret = smp_call_function_single(cpu, scf_handler_1, (void *)scfcp, 0);
381 		if (!ret) {
382 			if (use_cpus_read_lock)
383 				cpus_read_unlock();
384 			else
385 				preempt_enable();
386 			wait_for_completion(&scfcp->scfc_completion);
387 			if (use_cpus_read_lock)
388 				cpus_read_lock();
389 			else
390 				preempt_disable();
391 		} else {
392 			scfp->n_single_rpc_ofl++;
393 			kfree(scfcp);
394 			scfcp = NULL;
395 		}
396 		break;
397 	case SCF_PRIM_MANY:
398 		if (scfsp->scfs_wait)
399 			scfp->n_many_wait++;
400 		else
401 			scfp->n_many++;
402 		if (scfcp) {
403 			barrier(); // Prevent race-reduction compiler optimizations.
404 			scfcp->scfc_in = true;
405 		}
406 		smp_call_function_many(cpu_online_mask, scf_handler, scfcp, scfsp->scfs_wait);
407 		break;
408 	case SCF_PRIM_ALL:
409 		if (scfsp->scfs_wait)
410 			scfp->n_all_wait++;
411 		else
412 			scfp->n_all++;
413 		if (scfcp) {
414 			barrier(); // Prevent race-reduction compiler optimizations.
415 			scfcp->scfc_in = true;
416 		}
417 		smp_call_function(scf_handler, scfcp, scfsp->scfs_wait);
418 		break;
419 	default:
420 		WARN_ON_ONCE(1);
421 		if (scfcp)
422 			scfcp->scfc_out = true;
423 	}
424 	if (scfcp && scfsp->scfs_wait) {
425 		if (WARN_ON_ONCE((num_online_cpus() > 1 || scfsp->scfs_prim == SCF_PRIM_SINGLE) &&
426 				 !scfcp->scfc_out)) {
427 			pr_warn("%s: Memory-ordering failure, scfs_prim: %d.\n", __func__, scfsp->scfs_prim);
428 			atomic_inc(&n_mb_out_errs); // Leak rather than trash!
429 		} else {
430 			kfree(scfcp);
431 		}
432 		barrier(); // Prevent race-reduction compiler optimizations.
433 	}
434 	if (use_cpus_read_lock)
435 		cpus_read_unlock();
436 	else
437 		preempt_enable();
438 	if (allocfail)
439 		schedule_timeout_idle((1 + longwait) * HZ);  // Let no-wait handlers complete.
440 	else if (!(torture_random(trsp) & 0xfff))
441 		schedule_timeout_uninterruptible(1);
442 }
443 
444 // SCF test kthread.  Repeatedly does calls to members of the
445 // smp_call_function() family of functions.
446 static int scftorture_invoker(void *arg)
447 {
448 	int cpu;
449 	int curcpu;
450 	DEFINE_TORTURE_RANDOM(rand);
451 	struct scf_statistics *scfp = (struct scf_statistics *)arg;
452 	bool was_offline = false;
453 
454 	VERBOSE_SCFTORTOUT("scftorture_invoker %d: task started", scfp->cpu);
455 	cpu = scfp->cpu % nr_cpu_ids;
456 	WARN_ON_ONCE(set_cpus_allowed_ptr(current, cpumask_of(cpu)));
457 	set_user_nice(current, MAX_NICE);
458 	if (holdoff)
459 		schedule_timeout_interruptible(holdoff * HZ);
460 
461 	VERBOSE_SCFTORTOUT("scftorture_invoker %d: Waiting for all SCF torturers from cpu %d", scfp->cpu, raw_smp_processor_id());
462 
463 	// Make sure that the CPU is affinitized appropriately during testing.
464 	curcpu = raw_smp_processor_id();
465 	WARN_ONCE(curcpu != scfp->cpu % nr_cpu_ids,
466 		  "%s: Wanted CPU %d, running on %d, nr_cpu_ids = %d\n",
467 		  __func__, scfp->cpu, curcpu, nr_cpu_ids);
468 
469 	if (!atomic_dec_return(&n_started))
470 		while (atomic_read_acquire(&n_started)) {
471 			if (torture_must_stop()) {
472 				VERBOSE_SCFTORTOUT("scftorture_invoker %d ended before starting", scfp->cpu);
473 				goto end;
474 			}
475 			schedule_timeout_uninterruptible(1);
476 		}
477 
478 	VERBOSE_SCFTORTOUT("scftorture_invoker %d started", scfp->cpu);
479 
480 	do {
481 		scftorture_invoke_one(scfp, &rand);
482 		while (cpu_is_offline(cpu) && !torture_must_stop()) {
483 			schedule_timeout_interruptible(HZ / 5);
484 			was_offline = true;
485 		}
486 		if (was_offline) {
487 			set_cpus_allowed_ptr(current, cpumask_of(cpu));
488 			was_offline = false;
489 		}
490 		cond_resched();
491 		stutter_wait("scftorture_invoker");
492 	} while (!torture_must_stop());
493 
494 	VERBOSE_SCFTORTOUT("scftorture_invoker %d ended", scfp->cpu);
495 end:
496 	torture_kthread_stopping("scftorture_invoker");
497 	return 0;
498 }
499 
500 static void
501 scftorture_print_module_parms(const char *tag)
502 {
503 	pr_alert(SCFTORT_FLAG
504 		 "--- %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,
505 		 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);
506 }
507 
508 static void scf_cleanup_handler(void *unused)
509 {
510 }
511 
512 static void scf_torture_cleanup(void)
513 {
514 	int i;
515 
516 	if (torture_cleanup_begin())
517 		return;
518 
519 	WRITE_ONCE(scfdone, true);
520 	if (nthreads && scf_stats_p)
521 		for (i = 0; i < nthreads; i++)
522 			torture_stop_kthread("scftorture_invoker", scf_stats_p[i].task);
523 	else
524 		goto end;
525 	smp_call_function(scf_cleanup_handler, NULL, 0);
526 	torture_stop_kthread(scf_torture_stats, scf_torture_stats_task);
527 	scf_torture_stats_print();  // -After- the stats thread is stopped!
528 	kfree(scf_stats_p);  // -After- the last stats print has completed!
529 	scf_stats_p = NULL;
530 
531 	if (atomic_read(&n_errs) || atomic_read(&n_mb_in_errs) || atomic_read(&n_mb_out_errs))
532 		scftorture_print_module_parms("End of test: FAILURE");
533 	else if (torture_onoff_failures())
534 		scftorture_print_module_parms("End of test: LOCK_HOTPLUG");
535 	else
536 		scftorture_print_module_parms("End of test: SUCCESS");
537 
538 end:
539 	torture_cleanup_end();
540 }
541 
542 static int __init scf_torture_init(void)
543 {
544 	long i;
545 	int firsterr = 0;
546 	unsigned long weight_resched1 = weight_resched;
547 	unsigned long weight_single1 = weight_single;
548 	unsigned long weight_single_rpc1 = weight_single_rpc;
549 	unsigned long weight_single_wait1 = weight_single_wait;
550 	unsigned long weight_many1 = weight_many;
551 	unsigned long weight_many_wait1 = weight_many_wait;
552 	unsigned long weight_all1 = weight_all;
553 	unsigned long weight_all_wait1 = weight_all_wait;
554 
555 	if (!torture_init_begin(SCFTORT_STRING, verbose))
556 		return -EBUSY;
557 
558 	scftorture_print_module_parms("Start of test");
559 
560 	if (weight_resched <= 0 &&
561 	    weight_single <= 0 && weight_single_rpc <= 0 && weight_single_wait <= 0 &&
562 	    weight_many <= 0 && weight_many_wait <= 0 &&
563 	    weight_all <= 0 && weight_all_wait <= 0) {
564 		weight_resched1 = weight_resched == 0 ? 0 : 2 * nr_cpu_ids;
565 		weight_single1 = weight_single == 0 ? 0 : 2 * nr_cpu_ids;
566 		weight_single_rpc1 = weight_single_rpc == 0 ? 0 : 2 * nr_cpu_ids;
567 		weight_single_wait1 = weight_single_wait == 0 ? 0 : 2 * nr_cpu_ids;
568 		weight_many1 = weight_many == 0 ? 0 : 2;
569 		weight_many_wait1 = weight_many_wait == 0 ? 0 : 2;
570 		weight_all1 = weight_all == 0 ? 0 : 1;
571 		weight_all_wait1 = weight_all_wait == 0 ? 0 : 1;
572 	} else {
573 		if (weight_resched == -1)
574 			weight_resched1 = 0;
575 		if (weight_single == -1)
576 			weight_single1 = 0;
577 		if (weight_single_rpc == -1)
578 			weight_single_rpc1 = 0;
579 		if (weight_single_wait == -1)
580 			weight_single_wait1 = 0;
581 		if (weight_many == -1)
582 			weight_many1 = 0;
583 		if (weight_many_wait == -1)
584 			weight_many_wait1 = 0;
585 		if (weight_all == -1)
586 			weight_all1 = 0;
587 		if (weight_all_wait == -1)
588 			weight_all_wait1 = 0;
589 	}
590 	if (weight_resched1 == 0 && weight_single1 == 0 && weight_single_rpc1 == 0 &&
591 	    weight_single_wait1 == 0 && weight_many1 == 0 && weight_many_wait1 == 0 &&
592 	    weight_all1 == 0 && weight_all_wait1 == 0) {
593 		SCFTORTOUT_ERRSTRING("all zero weights makes no sense");
594 		firsterr = -EINVAL;
595 		goto unwind;
596 	}
597 	if (IS_BUILTIN(CONFIG_SCF_TORTURE_TEST))
598 		scf_sel_add(weight_resched1, SCF_PRIM_RESCHED, false);
599 	else if (weight_resched1)
600 		SCFTORTOUT_ERRSTRING("built as module, weight_resched ignored");
601 	scf_sel_add(weight_single1, SCF_PRIM_SINGLE, false);
602 	scf_sel_add(weight_single_rpc1, SCF_PRIM_SINGLE_RPC, true);
603 	scf_sel_add(weight_single_wait1, SCF_PRIM_SINGLE, true);
604 	scf_sel_add(weight_many1, SCF_PRIM_MANY, false);
605 	scf_sel_add(weight_many_wait1, SCF_PRIM_MANY, true);
606 	scf_sel_add(weight_all1, SCF_PRIM_ALL, false);
607 	scf_sel_add(weight_all_wait1, SCF_PRIM_ALL, true);
608 	scf_sel_dump();
609 
610 	if (onoff_interval > 0) {
611 		firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval, NULL);
612 		if (torture_init_error(firsterr))
613 			goto unwind;
614 	}
615 	if (shutdown_secs > 0) {
616 		firsterr = torture_shutdown_init(shutdown_secs, scf_torture_cleanup);
617 		if (torture_init_error(firsterr))
618 			goto unwind;
619 	}
620 	if (stutter > 0) {
621 		firsterr = torture_stutter_init(stutter, stutter);
622 		if (torture_init_error(firsterr))
623 			goto unwind;
624 	}
625 
626 	// Worker tasks invoking smp_call_function().
627 	if (nthreads < 0)
628 		nthreads = num_online_cpus();
629 	scf_stats_p = kcalloc(nthreads, sizeof(scf_stats_p[0]), GFP_KERNEL);
630 	if (!scf_stats_p) {
631 		SCFTORTOUT_ERRSTRING("out of memory");
632 		firsterr = -ENOMEM;
633 		goto unwind;
634 	}
635 
636 	VERBOSE_SCFTORTOUT("Starting %d smp_call_function() threads", nthreads);
637 
638 	atomic_set(&n_started, nthreads);
639 	for (i = 0; i < nthreads; i++) {
640 		scf_stats_p[i].cpu = i;
641 		firsterr = torture_create_kthread(scftorture_invoker, (void *)&scf_stats_p[i],
642 						  scf_stats_p[i].task);
643 		if (torture_init_error(firsterr))
644 			goto unwind;
645 	}
646 	if (stat_interval > 0) {
647 		firsterr = torture_create_kthread(scf_torture_stats, NULL, scf_torture_stats_task);
648 		if (torture_init_error(firsterr))
649 			goto unwind;
650 	}
651 
652 	torture_init_end();
653 	return 0;
654 
655 unwind:
656 	torture_init_end();
657 	scf_torture_cleanup();
658 	if (shutdown_secs) {
659 		WARN_ON(!IS_MODULE(CONFIG_SCF_TORTURE_TEST));
660 		kernel_power_off();
661 	}
662 	return firsterr;
663 }
664 
665 module_init(scf_torture_init);
666 module_exit(scf_torture_cleanup);
667