1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Module-based API test facility for ww_mutexes
4 */
5
6 #include <linux/kernel.h>
7
8 #include <linux/completion.h>
9 #include <linux/delay.h>
10 #include <linux/kthread.h>
11 #include <linux/module.h>
12 #include <linux/random.h>
13 #include <linux/slab.h>
14 #include <linux/ww_mutex.h>
15
16 static DEFINE_WD_CLASS(ww_class);
17 struct workqueue_struct *wq;
18
19 #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
20 #define ww_acquire_init_noinject(a, b) do { \
21 ww_acquire_init((a), (b)); \
22 (a)->deadlock_inject_countdown = ~0U; \
23 } while (0)
24 #else
25 #define ww_acquire_init_noinject(a, b) ww_acquire_init((a), (b))
26 #endif
27
28 struct test_mutex {
29 struct work_struct work;
30 struct ww_mutex mutex;
31 struct completion ready, go, done;
32 unsigned int flags;
33 };
34
35 #define TEST_MTX_SPIN BIT(0)
36 #define TEST_MTX_TRY BIT(1)
37 #define TEST_MTX_CTX BIT(2)
38 #define __TEST_MTX_LAST BIT(3)
39
test_mutex_work(struct work_struct * work)40 static void test_mutex_work(struct work_struct *work)
41 {
42 struct test_mutex *mtx = container_of(work, typeof(*mtx), work);
43
44 complete(&mtx->ready);
45 wait_for_completion(&mtx->go);
46
47 if (mtx->flags & TEST_MTX_TRY) {
48 while (!ww_mutex_trylock(&mtx->mutex, NULL))
49 cond_resched();
50 } else {
51 ww_mutex_lock(&mtx->mutex, NULL);
52 }
53 complete(&mtx->done);
54 ww_mutex_unlock(&mtx->mutex);
55 }
56
__test_mutex(unsigned int flags)57 static int __test_mutex(unsigned int flags)
58 {
59 #define TIMEOUT (HZ / 16)
60 struct test_mutex mtx;
61 struct ww_acquire_ctx ctx;
62 int ret;
63
64 ww_mutex_init(&mtx.mutex, &ww_class);
65 ww_acquire_init(&ctx, &ww_class);
66
67 INIT_WORK_ONSTACK(&mtx.work, test_mutex_work);
68 init_completion(&mtx.ready);
69 init_completion(&mtx.go);
70 init_completion(&mtx.done);
71 mtx.flags = flags;
72
73 schedule_work(&mtx.work);
74
75 wait_for_completion(&mtx.ready);
76 ww_mutex_lock(&mtx.mutex, (flags & TEST_MTX_CTX) ? &ctx : NULL);
77 complete(&mtx.go);
78 if (flags & TEST_MTX_SPIN) {
79 unsigned long timeout = jiffies + TIMEOUT;
80
81 ret = 0;
82 do {
83 if (completion_done(&mtx.done)) {
84 ret = -EINVAL;
85 break;
86 }
87 cond_resched();
88 } while (time_before(jiffies, timeout));
89 } else {
90 ret = wait_for_completion_timeout(&mtx.done, TIMEOUT);
91 }
92 ww_mutex_unlock(&mtx.mutex);
93 ww_acquire_fini(&ctx);
94
95 if (ret) {
96 pr_err("%s(flags=%x): mutual exclusion failure\n",
97 __func__, flags);
98 ret = -EINVAL;
99 }
100
101 flush_work(&mtx.work);
102 destroy_work_on_stack(&mtx.work);
103 return ret;
104 #undef TIMEOUT
105 }
106
test_mutex(void)107 static int test_mutex(void)
108 {
109 int ret;
110 int i;
111
112 for (i = 0; i < __TEST_MTX_LAST; i++) {
113 ret = __test_mutex(i);
114 if (ret)
115 return ret;
116 }
117
118 return 0;
119 }
120
test_aa(bool trylock)121 static int test_aa(bool trylock)
122 {
123 struct ww_mutex mutex;
124 struct ww_acquire_ctx ctx;
125 int ret;
126 const char *from = trylock ? "trylock" : "lock";
127
128 ww_mutex_init(&mutex, &ww_class);
129 ww_acquire_init(&ctx, &ww_class);
130
131 if (!trylock) {
132 ret = ww_mutex_lock(&mutex, &ctx);
133 if (ret) {
134 pr_err("%s: initial lock failed!\n", __func__);
135 goto out;
136 }
137 } else {
138 ret = !ww_mutex_trylock(&mutex, &ctx);
139 if (ret) {
140 pr_err("%s: initial trylock failed!\n", __func__);
141 goto out;
142 }
143 }
144
145 if (ww_mutex_trylock(&mutex, NULL)) {
146 pr_err("%s: trylocked itself without context from %s!\n", __func__, from);
147 ww_mutex_unlock(&mutex);
148 ret = -EINVAL;
149 goto out;
150 }
151
152 if (ww_mutex_trylock(&mutex, &ctx)) {
153 pr_err("%s: trylocked itself with context from %s!\n", __func__, from);
154 ww_mutex_unlock(&mutex);
155 ret = -EINVAL;
156 goto out;
157 }
158
159 ret = ww_mutex_lock(&mutex, &ctx);
160 if (ret != -EALREADY) {
161 pr_err("%s: missed deadlock for recursing, ret=%d from %s\n",
162 __func__, ret, from);
163 if (!ret)
164 ww_mutex_unlock(&mutex);
165 ret = -EINVAL;
166 goto out;
167 }
168
169 ww_mutex_unlock(&mutex);
170 ret = 0;
171 out:
172 ww_acquire_fini(&ctx);
173 return ret;
174 }
175
176 struct test_abba {
177 struct work_struct work;
178 struct ww_mutex a_mutex;
179 struct ww_mutex b_mutex;
180 struct completion a_ready;
181 struct completion b_ready;
182 bool resolve, trylock;
183 int result;
184 };
185
test_abba_work(struct work_struct * work)186 static void test_abba_work(struct work_struct *work)
187 {
188 struct test_abba *abba = container_of(work, typeof(*abba), work);
189 struct ww_acquire_ctx ctx;
190 int err;
191
192 ww_acquire_init_noinject(&ctx, &ww_class);
193 if (!abba->trylock)
194 ww_mutex_lock(&abba->b_mutex, &ctx);
195 else
196 WARN_ON(!ww_mutex_trylock(&abba->b_mutex, &ctx));
197
198 WARN_ON(READ_ONCE(abba->b_mutex.ctx) != &ctx);
199
200 complete(&abba->b_ready);
201 wait_for_completion(&abba->a_ready);
202
203 err = ww_mutex_lock(&abba->a_mutex, &ctx);
204 if (abba->resolve && err == -EDEADLK) {
205 ww_mutex_unlock(&abba->b_mutex);
206 ww_mutex_lock_slow(&abba->a_mutex, &ctx);
207 err = ww_mutex_lock(&abba->b_mutex, &ctx);
208 }
209
210 if (!err)
211 ww_mutex_unlock(&abba->a_mutex);
212 ww_mutex_unlock(&abba->b_mutex);
213 ww_acquire_fini(&ctx);
214
215 abba->result = err;
216 }
217
test_abba(bool trylock,bool resolve)218 static int test_abba(bool trylock, bool resolve)
219 {
220 struct test_abba abba;
221 struct ww_acquire_ctx ctx;
222 int err, ret;
223
224 ww_mutex_init(&abba.a_mutex, &ww_class);
225 ww_mutex_init(&abba.b_mutex, &ww_class);
226 INIT_WORK_ONSTACK(&abba.work, test_abba_work);
227 init_completion(&abba.a_ready);
228 init_completion(&abba.b_ready);
229 abba.trylock = trylock;
230 abba.resolve = resolve;
231
232 schedule_work(&abba.work);
233
234 ww_acquire_init_noinject(&ctx, &ww_class);
235 if (!trylock)
236 ww_mutex_lock(&abba.a_mutex, &ctx);
237 else
238 WARN_ON(!ww_mutex_trylock(&abba.a_mutex, &ctx));
239
240 WARN_ON(READ_ONCE(abba.a_mutex.ctx) != &ctx);
241
242 complete(&abba.a_ready);
243 wait_for_completion(&abba.b_ready);
244
245 err = ww_mutex_lock(&abba.b_mutex, &ctx);
246 if (resolve && err == -EDEADLK) {
247 ww_mutex_unlock(&abba.a_mutex);
248 ww_mutex_lock_slow(&abba.b_mutex, &ctx);
249 err = ww_mutex_lock(&abba.a_mutex, &ctx);
250 }
251
252 if (!err)
253 ww_mutex_unlock(&abba.b_mutex);
254 ww_mutex_unlock(&abba.a_mutex);
255 ww_acquire_fini(&ctx);
256
257 flush_work(&abba.work);
258 destroy_work_on_stack(&abba.work);
259
260 ret = 0;
261 if (resolve) {
262 if (err || abba.result) {
263 pr_err("%s: failed to resolve ABBA deadlock, A err=%d, B err=%d\n",
264 __func__, err, abba.result);
265 ret = -EINVAL;
266 }
267 } else {
268 if (err != -EDEADLK && abba.result != -EDEADLK) {
269 pr_err("%s: missed ABBA deadlock, A err=%d, B err=%d\n",
270 __func__, err, abba.result);
271 ret = -EINVAL;
272 }
273 }
274 return ret;
275 }
276
277 struct test_cycle {
278 struct work_struct work;
279 struct ww_mutex a_mutex;
280 struct ww_mutex *b_mutex;
281 struct completion *a_signal;
282 struct completion b_signal;
283 int result;
284 };
285
test_cycle_work(struct work_struct * work)286 static void test_cycle_work(struct work_struct *work)
287 {
288 struct test_cycle *cycle = container_of(work, typeof(*cycle), work);
289 struct ww_acquire_ctx ctx;
290 int err, erra = 0;
291
292 ww_acquire_init_noinject(&ctx, &ww_class);
293 ww_mutex_lock(&cycle->a_mutex, &ctx);
294
295 complete(cycle->a_signal);
296 wait_for_completion(&cycle->b_signal);
297
298 err = ww_mutex_lock(cycle->b_mutex, &ctx);
299 if (err == -EDEADLK) {
300 err = 0;
301 ww_mutex_unlock(&cycle->a_mutex);
302 ww_mutex_lock_slow(cycle->b_mutex, &ctx);
303 erra = ww_mutex_lock(&cycle->a_mutex, &ctx);
304 }
305
306 if (!err)
307 ww_mutex_unlock(cycle->b_mutex);
308 if (!erra)
309 ww_mutex_unlock(&cycle->a_mutex);
310 ww_acquire_fini(&ctx);
311
312 cycle->result = err ?: erra;
313 }
314
__test_cycle(unsigned int nthreads)315 static int __test_cycle(unsigned int nthreads)
316 {
317 struct test_cycle *cycles;
318 unsigned int n, last = nthreads - 1;
319 int ret;
320
321 cycles = kmalloc_array(nthreads, sizeof(*cycles), GFP_KERNEL);
322 if (!cycles)
323 return -ENOMEM;
324
325 for (n = 0; n < nthreads; n++) {
326 struct test_cycle *cycle = &cycles[n];
327
328 ww_mutex_init(&cycle->a_mutex, &ww_class);
329 if (n == last)
330 cycle->b_mutex = &cycles[0].a_mutex;
331 else
332 cycle->b_mutex = &cycles[n + 1].a_mutex;
333
334 if (n == 0)
335 cycle->a_signal = &cycles[last].b_signal;
336 else
337 cycle->a_signal = &cycles[n - 1].b_signal;
338 init_completion(&cycle->b_signal);
339
340 INIT_WORK(&cycle->work, test_cycle_work);
341 cycle->result = 0;
342 }
343
344 for (n = 0; n < nthreads; n++)
345 queue_work(wq, &cycles[n].work);
346
347 flush_workqueue(wq);
348
349 ret = 0;
350 for (n = 0; n < nthreads; n++) {
351 struct test_cycle *cycle = &cycles[n];
352
353 if (!cycle->result)
354 continue;
355
356 pr_err("cyclic deadlock not resolved, ret[%d/%d] = %d\n",
357 n, nthreads, cycle->result);
358 ret = -EINVAL;
359 break;
360 }
361
362 for (n = 0; n < nthreads; n++)
363 ww_mutex_destroy(&cycles[n].a_mutex);
364 kfree(cycles);
365 return ret;
366 }
367
test_cycle(unsigned int ncpus)368 static int test_cycle(unsigned int ncpus)
369 {
370 unsigned int n;
371 int ret;
372
373 for (n = 2; n <= ncpus + 1; n++) {
374 ret = __test_cycle(n);
375 if (ret)
376 return ret;
377 }
378
379 return 0;
380 }
381
382 struct stress {
383 struct work_struct work;
384 struct ww_mutex *locks;
385 unsigned long timeout;
386 int nlocks;
387 };
388
get_random_order(int count)389 static int *get_random_order(int count)
390 {
391 int *order;
392 int n, r, tmp;
393
394 order = kmalloc_array(count, sizeof(*order), GFP_KERNEL);
395 if (!order)
396 return order;
397
398 for (n = 0; n < count; n++)
399 order[n] = n;
400
401 for (n = count - 1; n > 1; n--) {
402 r = get_random_u32_below(n + 1);
403 if (r != n) {
404 tmp = order[n];
405 order[n] = order[r];
406 order[r] = tmp;
407 }
408 }
409
410 return order;
411 }
412
dummy_load(struct stress * stress)413 static void dummy_load(struct stress *stress)
414 {
415 usleep_range(1000, 2000);
416 }
417
stress_inorder_work(struct work_struct * work)418 static void stress_inorder_work(struct work_struct *work)
419 {
420 struct stress *stress = container_of(work, typeof(*stress), work);
421 const int nlocks = stress->nlocks;
422 struct ww_mutex *locks = stress->locks;
423 struct ww_acquire_ctx ctx;
424 int *order;
425
426 order = get_random_order(nlocks);
427 if (!order)
428 return;
429
430 do {
431 int contended = -1;
432 int n, err;
433
434 ww_acquire_init(&ctx, &ww_class);
435 retry:
436 err = 0;
437 for (n = 0; n < nlocks; n++) {
438 if (n == contended)
439 continue;
440
441 err = ww_mutex_lock(&locks[order[n]], &ctx);
442 if (err < 0)
443 break;
444 }
445 if (!err)
446 dummy_load(stress);
447
448 if (contended > n)
449 ww_mutex_unlock(&locks[order[contended]]);
450 contended = n;
451 while (n--)
452 ww_mutex_unlock(&locks[order[n]]);
453
454 if (err == -EDEADLK) {
455 ww_mutex_lock_slow(&locks[order[contended]], &ctx);
456 goto retry;
457 }
458
459 if (err) {
460 pr_err_once("stress (%s) failed with %d\n",
461 __func__, err);
462 break;
463 }
464
465 ww_acquire_fini(&ctx);
466 } while (!time_after(jiffies, stress->timeout));
467
468 kfree(order);
469 }
470
471 struct reorder_lock {
472 struct list_head link;
473 struct ww_mutex *lock;
474 };
475
stress_reorder_work(struct work_struct * work)476 static void stress_reorder_work(struct work_struct *work)
477 {
478 struct stress *stress = container_of(work, typeof(*stress), work);
479 LIST_HEAD(locks);
480 struct ww_acquire_ctx ctx;
481 struct reorder_lock *ll, *ln;
482 int *order;
483 int n, err;
484
485 order = get_random_order(stress->nlocks);
486 if (!order)
487 return;
488
489 for (n = 0; n < stress->nlocks; n++) {
490 ll = kmalloc(sizeof(*ll), GFP_KERNEL);
491 if (!ll)
492 goto out;
493
494 ll->lock = &stress->locks[order[n]];
495 list_add(&ll->link, &locks);
496 }
497 kfree(order);
498 order = NULL;
499
500 do {
501 ww_acquire_init(&ctx, &ww_class);
502
503 list_for_each_entry(ll, &locks, link) {
504 err = ww_mutex_lock(ll->lock, &ctx);
505 if (!err)
506 continue;
507
508 ln = ll;
509 list_for_each_entry_continue_reverse(ln, &locks, link)
510 ww_mutex_unlock(ln->lock);
511
512 if (err != -EDEADLK) {
513 pr_err_once("stress (%s) failed with %d\n",
514 __func__, err);
515 break;
516 }
517
518 ww_mutex_lock_slow(ll->lock, &ctx);
519 list_move(&ll->link, &locks); /* restarts iteration */
520 }
521
522 dummy_load(stress);
523 list_for_each_entry(ll, &locks, link)
524 ww_mutex_unlock(ll->lock);
525
526 ww_acquire_fini(&ctx);
527 } while (!time_after(jiffies, stress->timeout));
528
529 out:
530 list_for_each_entry_safe(ll, ln, &locks, link)
531 kfree(ll);
532 kfree(order);
533 }
534
stress_one_work(struct work_struct * work)535 static void stress_one_work(struct work_struct *work)
536 {
537 struct stress *stress = container_of(work, typeof(*stress), work);
538 const int nlocks = stress->nlocks;
539 struct ww_mutex *lock = stress->locks + get_random_u32_below(nlocks);
540 int err;
541
542 do {
543 err = ww_mutex_lock(lock, NULL);
544 if (!err) {
545 dummy_load(stress);
546 ww_mutex_unlock(lock);
547 } else {
548 pr_err_once("stress (%s) failed with %d\n",
549 __func__, err);
550 break;
551 }
552 } while (!time_after(jiffies, stress->timeout));
553 }
554
555 #define STRESS_INORDER BIT(0)
556 #define STRESS_REORDER BIT(1)
557 #define STRESS_ONE BIT(2)
558 #define STRESS_ALL (STRESS_INORDER | STRESS_REORDER | STRESS_ONE)
559
stress(int nlocks,int nthreads,unsigned int flags)560 static int stress(int nlocks, int nthreads, unsigned int flags)
561 {
562 struct ww_mutex *locks;
563 struct stress *stress_array;
564 int n, count;
565
566 locks = kmalloc_array(nlocks, sizeof(*locks), GFP_KERNEL);
567 if (!locks)
568 return -ENOMEM;
569
570 stress_array = kmalloc_array(nthreads, sizeof(*stress_array),
571 GFP_KERNEL);
572 if (!stress_array) {
573 kfree(locks);
574 return -ENOMEM;
575 }
576
577 for (n = 0; n < nlocks; n++)
578 ww_mutex_init(&locks[n], &ww_class);
579
580 count = 0;
581 for (n = 0; nthreads; n++) {
582 struct stress *stress;
583 void (*fn)(struct work_struct *work);
584
585 fn = NULL;
586 switch (n & 3) {
587 case 0:
588 if (flags & STRESS_INORDER)
589 fn = stress_inorder_work;
590 break;
591 case 1:
592 if (flags & STRESS_REORDER)
593 fn = stress_reorder_work;
594 break;
595 case 2:
596 if (flags & STRESS_ONE)
597 fn = stress_one_work;
598 break;
599 }
600
601 if (!fn)
602 continue;
603
604 stress = &stress_array[count++];
605
606 INIT_WORK(&stress->work, fn);
607 stress->locks = locks;
608 stress->nlocks = nlocks;
609 stress->timeout = jiffies + 2*HZ;
610
611 queue_work(wq, &stress->work);
612 nthreads--;
613 }
614
615 flush_workqueue(wq);
616
617 for (n = 0; n < nlocks; n++)
618 ww_mutex_destroy(&locks[n]);
619 kfree(stress_array);
620 kfree(locks);
621
622 return 0;
623 }
624
test_ww_mutex_init(void)625 static int __init test_ww_mutex_init(void)
626 {
627 int ncpus = num_online_cpus();
628 int ret, i;
629
630 printk(KERN_INFO "Beginning ww mutex selftests\n");
631
632 wq = alloc_workqueue("test-ww_mutex", WQ_UNBOUND, 0);
633 if (!wq)
634 return -ENOMEM;
635
636 ret = test_mutex();
637 if (ret)
638 return ret;
639
640 ret = test_aa(false);
641 if (ret)
642 return ret;
643
644 ret = test_aa(true);
645 if (ret)
646 return ret;
647
648 for (i = 0; i < 4; i++) {
649 ret = test_abba(i & 1, i & 2);
650 if (ret)
651 return ret;
652 }
653
654 ret = test_cycle(ncpus);
655 if (ret)
656 return ret;
657
658 ret = stress(16, 2*ncpus, STRESS_INORDER);
659 if (ret)
660 return ret;
661
662 ret = stress(16, 2*ncpus, STRESS_REORDER);
663 if (ret)
664 return ret;
665
666 ret = stress(2047, hweight32(STRESS_ALL)*ncpus, STRESS_ALL);
667 if (ret)
668 return ret;
669
670 printk(KERN_INFO "All ww mutex selftests passed\n");
671 return 0;
672 }
673
test_ww_mutex_exit(void)674 static void __exit test_ww_mutex_exit(void)
675 {
676 destroy_workqueue(wq);
677 }
678
679 module_init(test_ww_mutex_init);
680 module_exit(test_ww_mutex_exit);
681
682 MODULE_LICENSE("GPL");
683 MODULE_AUTHOR("Intel Corporation");
684