2 * Copyright (C) 2012-2014 Canonical Ltd (Maarten Lankhorst)
4 * Based on bo.c which bears the following copyright notice,
5 * but is dual licensed:
7 * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
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:
18 * The above copyright notice and this permission notice (including the
19 * next paragraph) shall be included in all copies or substantial portions
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.
30 **************************************************************************/
32 * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
35 #include <linux/reservation.h>
36 #include <linux/export.h>
39 * DOC: Reservation Object Overview
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
49 DEFINE_WW_CLASS(reservation_ww_class);
50 EXPORT_SYMBOL(reservation_ww_class);
52 struct lock_class_key reservation_seqcount_class;
53 EXPORT_SYMBOL(reservation_seqcount_class);
55 const char reservation_seqcount_string[] = "reservation_seqcount";
56 EXPORT_SYMBOL(reservation_seqcount_string);
59 * reservation_object_reserve_shared - Reserve space to add a shared
60 * fence to a reservation_object.
61 * @obj: reservation object
63 * Should be called before reservation_object_add_shared_fence(). Must
64 * be called with obj->lock held.
67 * Zero for success, or -errno
69 int reservation_object_reserve_shared(struct reservation_object *obj)
71 struct reservation_object_list *fobj, *old;
74 old = reservation_object_get_list(obj);
76 if (old && old->shared_max) {
77 if (old->shared_count < old->shared_max) {
78 /* perform an in-place update */
83 max = old->shared_max * 2;
88 * resize obj->staged or allocate if it doesn't exist,
89 * noop if already correct size
91 fobj = krealloc(obj->staged, offsetof(typeof(*fobj), shared[max]),
97 fobj->shared_max = max;
100 EXPORT_SYMBOL(reservation_object_reserve_shared);
103 reservation_object_add_shared_inplace(struct reservation_object *obj,
104 struct reservation_object_list *fobj,
112 write_seqcount_begin(&obj->seq);
114 for (i = 0; i < fobj->shared_count; ++i) {
115 struct fence *old_fence;
117 old_fence = rcu_dereference_protected(fobj->shared[i],
118 reservation_object_held(obj));
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);
126 fence_put(old_fence);
132 * memory barrier is added by write_seqcount_begin,
133 * fobj->shared_count is protected by this lock too
135 RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
136 fobj->shared_count++;
138 write_seqcount_end(&obj->seq);
143 reservation_object_add_shared_replace(struct reservation_object *obj,
144 struct reservation_object_list *old,
145 struct reservation_object_list *fobj,
149 struct fence *old_fence = NULL;
154 RCU_INIT_POINTER(fobj->shared[0], fence);
155 fobj->shared_count = 1;
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
165 fobj->shared_count = old->shared_count;
167 for (i = 0; i < old->shared_count; ++i) {
170 check = rcu_dereference_protected(old->shared[i],
171 reservation_object_held(obj));
173 if (!old_fence && check->context == fence->context) {
175 RCU_INIT_POINTER(fobj->shared[i], fence);
177 RCU_INIT_POINTER(fobj->shared[i], check);
180 RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
181 fobj->shared_count++;
186 write_seqcount_begin(&obj->seq);
188 * RCU_INIT_POINTER can be used here,
189 * seqcount provides the necessary barriers
191 RCU_INIT_POINTER(obj->fence, fobj);
192 write_seqcount_end(&obj->seq);
199 fence_put(old_fence);
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
207 * Add a fence to a shared slot, obj->lock must be held, and
208 * reservation_object_reserve_shared_fence has been called.
210 void reservation_object_add_shared_fence(struct reservation_object *obj,
213 struct reservation_object_list *old, *fobj = obj->staged;
215 old = reservation_object_get_list(obj);
219 BUG_ON(old->shared_count >= old->shared_max);
220 reservation_object_add_shared_inplace(obj, old, fence);
222 reservation_object_add_shared_replace(obj, old, fobj, fence);
224 EXPORT_SYMBOL(reservation_object_add_shared_fence);
227 * reservation_object_add_excl_fence - Add an exclusive fence.
228 * @obj: the reservation object
229 * @fence: the shared fence to add
231 * Add a fence to the exclusive slot. The obj->lock must be held.
233 void reservation_object_add_excl_fence(struct reservation_object *obj,
236 struct fence *old_fence = reservation_object_get_excl(obj);
237 struct reservation_object_list *old;
240 old = reservation_object_get_list(obj);
242 i = old->shared_count;
248 write_seqcount_begin(&obj->seq);
249 /* write_seqcount_begin provides the necessary memory barrier */
250 RCU_INIT_POINTER(obj->fence_excl, fence);
252 old->shared_count = 0;
253 write_seqcount_end(&obj->seq);
256 /* inplace update, no shared fences */
258 fence_put(rcu_dereference_protected(old->shared[i],
259 reservation_object_held(obj)));
262 fence_put(old_fence);
264 EXPORT_SYMBOL(reservation_object_add_excl_fence);
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)
278 int reservation_object_get_fences_rcu(struct reservation_object *obj,
279 struct fence **pfence_excl,
280 unsigned *pshared_count,
281 struct fence ***pshared)
283 unsigned shared_count = 0;
285 struct fence **shared = NULL, *fence_excl = NULL;
289 struct reservation_object_list *fobj;
292 seq = read_seqcount_begin(&obj->seq);
296 fobj = rcu_dereference(obj->fence);
298 struct fence **nshared;
299 size_t sz = sizeof(*shared) * fobj->shared_max;
301 nshared = krealloc(shared, sz,
302 GFP_NOWAIT | __GFP_NOWARN);
305 nshared = krealloc(shared, sz, GFP_KERNEL);
316 memcpy(shared, fobj->shared, sz);
317 shared_count = fobj->shared_count;
320 fence_excl = rcu_dereference(obj->fence_excl);
322 retry = read_seqcount_retry(&obj->seq, seq);
326 if (!fence_excl || fence_get_rcu(fence_excl)) {
329 for (i = 0; i < shared_count; ++i) {
330 if (fence_get_rcu(shared[i]))
333 /* uh oh, refcount failed, abort and retry */
335 fence_put(shared[i]);
338 fence_put(fence_excl);
351 *pshared_count = shared_count;
358 *pfence_excl = fence_excl;
362 EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
365 * reservation_object_wait_timeout_rcu - Wait on reservation's objects
366 * shared and/or exclusive fences.
367 * @obj: the reservation object
368 * @wait_all: if true, wait on all fences, else wait on just exclusive fence
369 * @intr: if true, do interruptible wait
370 * @timeout: timeout value in jiffies or zero to return immediately
373 * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
374 * greater than zer on success.
376 long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
377 bool wait_all, bool intr,
378 unsigned long timeout)
381 unsigned seq, shared_count, i = 0;
385 return reservation_object_test_signaled_rcu(obj, wait_all);
390 seq = read_seqcount_begin(&obj->seq);
394 struct reservation_object_list *fobj =
395 rcu_dereference(obj->fence);
398 shared_count = fobj->shared_count;
400 if (read_seqcount_retry(&obj->seq, seq))
403 for (i = 0; i < shared_count; ++i) {
404 struct fence *lfence = rcu_dereference(fobj->shared[i]);
406 if (test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags))
409 if (!fence_get_rcu(lfence))
412 if (fence_is_signaled(lfence)) {
423 struct fence *fence_excl = rcu_dereference(obj->fence_excl);
425 if (read_seqcount_retry(&obj->seq, seq))
429 !test_bit(FENCE_FLAG_SIGNALED_BIT, &fence_excl->flags)) {
430 if (!fence_get_rcu(fence_excl))
433 if (fence_is_signaled(fence_excl))
434 fence_put(fence_excl);
442 ret = fence_wait_timeout(fence, intr, ret);
444 if (ret > 0 && wait_all && (i + 1 < shared_count))
453 EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu);
457 reservation_object_test_signaled_single(struct fence *passed_fence)
459 struct fence *fence, *lfence = passed_fence;
462 if (!test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
463 fence = fence_get_rcu(lfence);
467 ret = !!fence_is_signaled(fence);
474 * reservation_object_test_signaled_rcu - Test if a reservation object's
475 * fences have been signaled.
476 * @obj: the reservation object
477 * @test_all: if true, test all fences, otherwise only test the exclusive
481 * true if all fences signaled, else false
483 bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
486 unsigned seq, shared_count;
491 seq = read_seqcount_begin(&obj->seq);
497 struct reservation_object_list *fobj =
498 rcu_dereference(obj->fence);
501 shared_count = fobj->shared_count;
503 if (read_seqcount_retry(&obj->seq, seq))
506 for (i = 0; i < shared_count; ++i) {
507 struct fence *fence = rcu_dereference(fobj->shared[i]);
509 ret = reservation_object_test_signaled_single(fence);
517 * There could be a read_seqcount_retry here, but nothing cares
518 * about whether it's the old or newer fence pointers that are
519 * signaled. That race could still have happened after checking
520 * read_seqcount_retry. If you care, use ww_mutex_lock.
525 struct fence *fence_excl = rcu_dereference(obj->fence_excl);
527 if (read_seqcount_retry(&obj->seq, seq))
531 ret = reservation_object_test_signaled_single(
545 EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);