1 /*
2 * Copyright (C) 2012-2014 Canonical Ltd (Maarten Lankhorst)
3 *
4 * Based on bo.c which bears the following copyright notice,
5 * but is dual licensed:
6 *
7 * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
8 * All Rights Reserved.
9 *
10 * Permission is hereby granted, free of charge, to any person obtaining a
11 * copy of this software and associated documentation files (the
12 * "Software"), to deal in the Software without restriction, including
13 * without limitation the rights to use, copy, modify, merge, publish,
14 * distribute, sub license, and/or sell copies of the Software, and to
15 * permit persons to whom the Software is furnished to do so, subject to
16 * the following conditions:
17 *
18 * The above copyright notice and this permission notice (including the
19 * next paragraph) shall be included in all copies or substantial portions
20 * of the Software.
21 *
22 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
23 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
24 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
25 * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
26 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
27 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
28 * USE OR OTHER DEALINGS IN THE SOFTWARE.
29 *
30 **************************************************************************/
31 /*
32 * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
33 */
34
35 #include <linux/reservation.h>
36 #include <linux/export.h>
37
38 /**
39 * DOC: Reservation Object Overview
40 *
41 * The reservation object provides a mechanism to manage shared and
42 * exclusive fences associated with a buffer. A reservation object
43 * can have attached one exclusive fence (normally associated with
44 * write operations) or N shared fences (read operations). The RCU
45 * mechanism is used to protect read access to fences from locked
46 * write-side updates.
47 */
48
49 DEFINE_WW_CLASS(reservation_ww_class);
50 EXPORT_SYMBOL(reservation_ww_class);
51
52 struct lock_class_key reservation_seqcount_class;
53 EXPORT_SYMBOL(reservation_seqcount_class);
54
55 const char reservation_seqcount_string[] = "reservation_seqcount";
56 EXPORT_SYMBOL(reservation_seqcount_string);
57
58 /**
59 * reservation_object_reserve_shared - Reserve space to add a shared
60 * fence to a reservation_object.
61 * @obj: reservation object
62 *
63 * Should be called before reservation_object_add_shared_fence(). Must
64 * be called with obj->lock held.
65 *
66 * RETURNS
67 * Zero for success, or -errno
68 */
reservation_object_reserve_shared(struct reservation_object * obj)69 int reservation_object_reserve_shared(struct reservation_object *obj)
70 {
71 struct reservation_object_list *fobj, *old;
72 u32 max;
73
74 old = reservation_object_get_list(obj);
75
76 if (old && old->shared_max) {
77 if (old->shared_count < old->shared_max) {
78 /* perform an in-place update */
79 kfree(obj->staged);
80 obj->staged = NULL;
81 return 0;
82 } else
83 max = old->shared_max * 2;
84 } else
85 max = 4;
86
87 /*
88 * resize obj->staged or allocate if it doesn't exist,
89 * noop if already correct size
90 */
91 fobj = krealloc(obj->staged, offsetof(typeof(*fobj), shared[max]),
92 GFP_KERNEL);
93 if (!fobj)
94 return -ENOMEM;
95
96 obj->staged = fobj;
97 fobj->shared_max = max;
98 return 0;
99 }
100 EXPORT_SYMBOL(reservation_object_reserve_shared);
101
102 static void
reservation_object_add_shared_inplace(struct reservation_object * obj,struct reservation_object_list * fobj,struct fence * fence)103 reservation_object_add_shared_inplace(struct reservation_object *obj,
104 struct reservation_object_list *fobj,
105 struct fence *fence)
106 {
107 u32 i;
108
109 fence_get(fence);
110
111 preempt_disable();
112 write_seqcount_begin(&obj->seq);
113
114 for (i = 0; i < fobj->shared_count; ++i) {
115 struct fence *old_fence;
116
117 old_fence = rcu_dereference_protected(fobj->shared[i],
118 reservation_object_held(obj));
119
120 if (old_fence->context == fence->context) {
121 /* memory barrier is added by write_seqcount_begin */
122 RCU_INIT_POINTER(fobj->shared[i], fence);
123 write_seqcount_end(&obj->seq);
124 preempt_enable();
125
126 fence_put(old_fence);
127 return;
128 }
129 }
130
131 /*
132 * memory barrier is added by write_seqcount_begin,
133 * fobj->shared_count is protected by this lock too
134 */
135 RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
136 fobj->shared_count++;
137
138 write_seqcount_end(&obj->seq);
139 preempt_enable();
140 }
141
142 static void
reservation_object_add_shared_replace(struct reservation_object * obj,struct reservation_object_list * old,struct reservation_object_list * fobj,struct fence * fence)143 reservation_object_add_shared_replace(struct reservation_object *obj,
144 struct reservation_object_list *old,
145 struct reservation_object_list *fobj,
146 struct fence *fence)
147 {
148 unsigned i;
149 struct fence *old_fence = NULL;
150
151 fence_get(fence);
152
153 if (!old) {
154 RCU_INIT_POINTER(fobj->shared[0], fence);
155 fobj->shared_count = 1;
156 goto done;
157 }
158
159 /*
160 * no need to bump fence refcounts, rcu_read access
161 * requires the use of kref_get_unless_zero, and the
162 * references from the old struct are carried over to
163 * the new.
164 */
165 fobj->shared_count = old->shared_count;
166
167 for (i = 0; i < old->shared_count; ++i) {
168 struct fence *check;
169
170 check = rcu_dereference_protected(old->shared[i],
171 reservation_object_held(obj));
172
173 if (!old_fence && check->context == fence->context) {
174 old_fence = check;
175 RCU_INIT_POINTER(fobj->shared[i], fence);
176 } else
177 RCU_INIT_POINTER(fobj->shared[i], check);
178 }
179 if (!old_fence) {
180 RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
181 fobj->shared_count++;
182 }
183
184 done:
185 preempt_disable();
186 write_seqcount_begin(&obj->seq);
187 /*
188 * RCU_INIT_POINTER can be used here,
189 * seqcount provides the necessary barriers
190 */
191 RCU_INIT_POINTER(obj->fence, fobj);
192 write_seqcount_end(&obj->seq);
193 preempt_enable();
194
195 if (old)
196 kfree_rcu(old, rcu);
197
198 if (old_fence)
199 fence_put(old_fence);
200 }
201
202 /**
203 * reservation_object_add_shared_fence - Add a fence to a shared slot
204 * @obj: the reservation object
205 * @fence: the shared fence to add
206 *
207 * Add a fence to a shared slot, obj->lock must be held, and
208 * reservation_object_reserve_shared() has been called.
209 */
reservation_object_add_shared_fence(struct reservation_object * obj,struct fence * fence)210 void reservation_object_add_shared_fence(struct reservation_object *obj,
211 struct fence *fence)
212 {
213 struct reservation_object_list *old, *fobj = obj->staged;
214
215 old = reservation_object_get_list(obj);
216 obj->staged = NULL;
217
218 if (!fobj) {
219 BUG_ON(old->shared_count >= old->shared_max);
220 reservation_object_add_shared_inplace(obj, old, fence);
221 } else
222 reservation_object_add_shared_replace(obj, old, fobj, fence);
223 }
224 EXPORT_SYMBOL(reservation_object_add_shared_fence);
225
226 /**
227 * reservation_object_add_excl_fence - Add an exclusive fence.
228 * @obj: the reservation object
229 * @fence: the shared fence to add
230 *
231 * Add a fence to the exclusive slot. The obj->lock must be held.
232 */
reservation_object_add_excl_fence(struct reservation_object * obj,struct fence * fence)233 void reservation_object_add_excl_fence(struct reservation_object *obj,
234 struct fence *fence)
235 {
236 struct fence *old_fence = reservation_object_get_excl(obj);
237 struct reservation_object_list *old;
238 u32 i = 0;
239
240 old = reservation_object_get_list(obj);
241 if (old)
242 i = old->shared_count;
243
244 if (fence)
245 fence_get(fence);
246
247 preempt_disable();
248 write_seqcount_begin(&obj->seq);
249 /* write_seqcount_begin provides the necessary memory barrier */
250 RCU_INIT_POINTER(obj->fence_excl, fence);
251 if (old)
252 old->shared_count = 0;
253 write_seqcount_end(&obj->seq);
254 preempt_enable();
255
256 /* inplace update, no shared fences */
257 while (i--)
258 fence_put(rcu_dereference_protected(old->shared[i],
259 reservation_object_held(obj)));
260
261 if (old_fence)
262 fence_put(old_fence);
263 }
264 EXPORT_SYMBOL(reservation_object_add_excl_fence);
265
266 /**
267 * reservation_object_get_fences_rcu - Get an object's shared and exclusive
268 * fences without update side lock held
269 * @obj: the reservation object
270 * @pfence_excl: the returned exclusive fence (or NULL)
271 * @pshared_count: the number of shared fences returned
272 * @pshared: the array of shared fence ptrs returned (array is krealloc'd to
273 * the required size, and must be freed by caller)
274 *
275 * RETURNS
276 * Zero or -errno
277 */
reservation_object_get_fences_rcu(struct reservation_object * obj,struct fence ** pfence_excl,unsigned * pshared_count,struct fence *** pshared)278 int reservation_object_get_fences_rcu(struct reservation_object *obj,
279 struct fence **pfence_excl,
280 unsigned *pshared_count,
281 struct fence ***pshared)
282 {
283 struct fence **shared = NULL;
284 struct fence *fence_excl;
285 unsigned int shared_count;
286 int ret = 1;
287
288 do {
289 struct reservation_object_list *fobj;
290 unsigned seq;
291 unsigned int i;
292
293 shared_count = i = 0;
294
295 rcu_read_lock();
296 seq = read_seqcount_begin(&obj->seq);
297
298 fence_excl = rcu_dereference(obj->fence_excl);
299 if (fence_excl && !fence_get_rcu(fence_excl))
300 goto unlock;
301
302 fobj = rcu_dereference(obj->fence);
303 if (fobj) {
304 struct fence **nshared;
305 size_t sz = sizeof(*shared) * fobj->shared_max;
306
307 nshared = krealloc(shared, sz,
308 GFP_NOWAIT | __GFP_NOWARN);
309 if (!nshared) {
310 rcu_read_unlock();
311 nshared = krealloc(shared, sz, GFP_KERNEL);
312 if (nshared) {
313 shared = nshared;
314 continue;
315 }
316
317 ret = -ENOMEM;
318 break;
319 }
320 shared = nshared;
321 shared_count = fobj->shared_count;
322
323 for (i = 0; i < shared_count; ++i) {
324 shared[i] = rcu_dereference(fobj->shared[i]);
325 if (!fence_get_rcu(shared[i]))
326 break;
327 }
328 }
329
330 if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
331 while (i--)
332 fence_put(shared[i]);
333 fence_put(fence_excl);
334 goto unlock;
335 }
336
337 ret = 0;
338 unlock:
339 rcu_read_unlock();
340 } while (ret);
341
342 if (!shared_count) {
343 kfree(shared);
344 shared = NULL;
345 }
346
347 *pshared_count = shared_count;
348 *pshared = shared;
349 *pfence_excl = fence_excl;
350
351 return ret;
352 }
353 EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
354
355 /**
356 * reservation_object_wait_timeout_rcu - Wait on reservation's objects
357 * shared and/or exclusive fences.
358 * @obj: the reservation object
359 * @wait_all: if true, wait on all fences, else wait on just exclusive fence
360 * @intr: if true, do interruptible wait
361 * @timeout: timeout value in jiffies or zero to return immediately
362 *
363 * RETURNS
364 * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
365 * greater than zer on success.
366 */
reservation_object_wait_timeout_rcu(struct reservation_object * obj,bool wait_all,bool intr,unsigned long timeout)367 long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
368 bool wait_all, bool intr,
369 unsigned long timeout)
370 {
371 struct fence *fence;
372 unsigned seq, shared_count, i = 0;
373 long ret = timeout ? timeout : 1;
374
375 retry:
376 fence = NULL;
377 shared_count = 0;
378 seq = read_seqcount_begin(&obj->seq);
379 rcu_read_lock();
380
381 if (wait_all) {
382 struct reservation_object_list *fobj =
383 rcu_dereference(obj->fence);
384
385 if (fobj)
386 shared_count = fobj->shared_count;
387
388 for (i = 0; i < shared_count; ++i) {
389 struct fence *lfence = rcu_dereference(fobj->shared[i]);
390
391 if (test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags))
392 continue;
393
394 if (!fence_get_rcu(lfence))
395 goto unlock_retry;
396
397 if (fence_is_signaled(lfence)) {
398 fence_put(lfence);
399 continue;
400 }
401
402 fence = lfence;
403 break;
404 }
405 }
406
407 if (!shared_count) {
408 struct fence *fence_excl = rcu_dereference(obj->fence_excl);
409
410 if (fence_excl &&
411 !test_bit(FENCE_FLAG_SIGNALED_BIT, &fence_excl->flags)) {
412 if (!fence_get_rcu(fence_excl))
413 goto unlock_retry;
414
415 if (fence_is_signaled(fence_excl))
416 fence_put(fence_excl);
417 else
418 fence = fence_excl;
419 }
420 }
421
422 rcu_read_unlock();
423 if (fence) {
424 if (read_seqcount_retry(&obj->seq, seq)) {
425 fence_put(fence);
426 goto retry;
427 }
428
429 ret = fence_wait_timeout(fence, intr, ret);
430 fence_put(fence);
431 if (ret > 0 && wait_all && (i + 1 < shared_count))
432 goto retry;
433 }
434 return ret;
435
436 unlock_retry:
437 rcu_read_unlock();
438 goto retry;
439 }
440 EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu);
441
442
443 static inline int
reservation_object_test_signaled_single(struct fence * passed_fence)444 reservation_object_test_signaled_single(struct fence *passed_fence)
445 {
446 struct fence *fence, *lfence = passed_fence;
447 int ret = 1;
448
449 if (!test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
450 fence = fence_get_rcu(lfence);
451 if (!fence)
452 return -1;
453
454 ret = !!fence_is_signaled(fence);
455 fence_put(fence);
456 }
457 return ret;
458 }
459
460 /**
461 * reservation_object_test_signaled_rcu - Test if a reservation object's
462 * fences have been signaled.
463 * @obj: the reservation object
464 * @test_all: if true, test all fences, otherwise only test the exclusive
465 * fence
466 *
467 * RETURNS
468 * true if all fences signaled, else false
469 */
reservation_object_test_signaled_rcu(struct reservation_object * obj,bool test_all)470 bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
471 bool test_all)
472 {
473 unsigned seq, shared_count;
474 int ret;
475
476 rcu_read_lock();
477 retry:
478 ret = true;
479 shared_count = 0;
480 seq = read_seqcount_begin(&obj->seq);
481
482 if (test_all) {
483 unsigned i;
484
485 struct reservation_object_list *fobj =
486 rcu_dereference(obj->fence);
487
488 if (fobj)
489 shared_count = fobj->shared_count;
490
491 for (i = 0; i < shared_count; ++i) {
492 struct fence *fence = rcu_dereference(fobj->shared[i]);
493
494 ret = reservation_object_test_signaled_single(fence);
495 if (ret < 0)
496 goto retry;
497 else if (!ret)
498 break;
499 }
500
501 if (read_seqcount_retry(&obj->seq, seq))
502 goto retry;
503 }
504
505 if (!shared_count) {
506 struct fence *fence_excl = rcu_dereference(obj->fence_excl);
507
508 if (fence_excl) {
509 ret = reservation_object_test_signaled_single(
510 fence_excl);
511 if (ret < 0)
512 goto retry;
513
514 if (read_seqcount_retry(&obj->seq, seq))
515 goto retry;
516 }
517 }
518
519 rcu_read_unlock();
520 return ret;
521 }
522 EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);
523