1 /*
2  * Header file for reservations for dma-buf and ttm
3  *
4  * Copyright(C) 2011 Linaro Limited. All rights reserved.
5  * Copyright (C) 2012-2013 Canonical Ltd
6  * Copyright (C) 2012 Texas Instruments
7  *
8  * Authors:
9  * Rob Clark <robdclark@gmail.com>
10  * Maarten Lankhorst <maarten.lankhorst@canonical.com>
11  * Thomas Hellstrom <thellstrom-at-vmware-dot-com>
12  *
13  * Based on bo.c which bears the following copyright notice,
14  * but is dual licensed:
15  *
16  * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
17  * All Rights Reserved.
18  *
19  * Permission is hereby granted, free of charge, to any person obtaining a
20  * copy of this software and associated documentation files (the
21  * "Software"), to deal in the Software without restriction, including
22  * without limitation the rights to use, copy, modify, merge, publish,
23  * distribute, sub license, and/or sell copies of the Software, and to
24  * permit persons to whom the Software is furnished to do so, subject to
25  * the following conditions:
26  *
27  * The above copyright notice and this permission notice (including the
28  * next paragraph) shall be included in all copies or substantial portions
29  * of the Software.
30  *
31  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
32  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
33  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
34  * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
35  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
36  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
37  * USE OR OTHER DEALINGS IN THE SOFTWARE.
38  */
39 #ifndef _LINUX_RESERVATION_H
40 #define _LINUX_RESERVATION_H
41 
42 #include <linux/ww_mutex.h>
43 #include <linux/fence.h>
44 #include <linux/slab.h>
45 #include <linux/seqlock.h>
46 #include <linux/rcupdate.h>
47 
48 extern struct ww_class reservation_ww_class;
49 extern struct lock_class_key reservation_seqcount_class;
50 extern const char reservation_seqcount_string[];
51 
52 /**
53  * struct reservation_object_list - a list of shared fences
54  * @rcu: for internal use
55  * @shared_count: table of shared fences
56  * @shared_max: for growing shared fence table
57  * @shared: shared fence table
58  */
59 struct reservation_object_list {
60 	struct rcu_head rcu;
61 	u32 shared_count, shared_max;
62 	struct fence __rcu *shared[];
63 };
64 
65 /**
66  * struct reservation_object - a reservation object manages fences for a buffer
67  * @lock: update side lock
68  * @seq: sequence count for managing RCU read-side synchronization
69  * @fence_excl: the exclusive fence, if there is one currently
70  * @fence: list of current shared fences
71  * @staged: staged copy of shared fences for RCU updates
72  */
73 struct reservation_object {
74 	struct ww_mutex lock;
75 	seqcount_t seq;
76 
77 	struct fence __rcu *fence_excl;
78 	struct reservation_object_list __rcu *fence;
79 	struct reservation_object_list *staged;
80 };
81 
82 #define reservation_object_held(obj) lockdep_is_held(&(obj)->lock.base)
83 #define reservation_object_assert_held(obj) \
84 	lockdep_assert_held(&(obj)->lock.base)
85 
86 /**
87  * reservation_object_init - initialize a reservation object
88  * @obj: the reservation object
89  */
90 static inline void
91 reservation_object_init(struct reservation_object *obj)
92 {
93 	ww_mutex_init(&obj->lock, &reservation_ww_class);
94 
95 	__seqcount_init(&obj->seq, reservation_seqcount_string, &reservation_seqcount_class);
96 	RCU_INIT_POINTER(obj->fence, NULL);
97 	RCU_INIT_POINTER(obj->fence_excl, NULL);
98 	obj->staged = NULL;
99 }
100 
101 /**
102  * reservation_object_fini - destroys a reservation object
103  * @obj: the reservation object
104  */
105 static inline void
106 reservation_object_fini(struct reservation_object *obj)
107 {
108 	int i;
109 	struct reservation_object_list *fobj;
110 	struct fence *excl;
111 
112 	/*
113 	 * This object should be dead and all references must have
114 	 * been released to it, so no need to be protected with rcu.
115 	 */
116 	excl = rcu_dereference_protected(obj->fence_excl, 1);
117 	if (excl)
118 		fence_put(excl);
119 
120 	fobj = rcu_dereference_protected(obj->fence, 1);
121 	if (fobj) {
122 		for (i = 0; i < fobj->shared_count; ++i)
123 			fence_put(rcu_dereference_protected(fobj->shared[i], 1));
124 
125 		kfree(fobj);
126 	}
127 	kfree(obj->staged);
128 
129 	ww_mutex_destroy(&obj->lock);
130 }
131 
132 /**
133  * reservation_object_get_list - get the reservation object's
134  * shared fence list, with update-side lock held
135  * @obj: the reservation object
136  *
137  * Returns the shared fence list.  Does NOT take references to
138  * the fence.  The obj->lock must be held.
139  */
140 static inline struct reservation_object_list *
141 reservation_object_get_list(struct reservation_object *obj)
142 {
143 	return rcu_dereference_protected(obj->fence,
144 					 reservation_object_held(obj));
145 }
146 
147 /**
148  * reservation_object_get_excl - get the reservation object's
149  * exclusive fence, with update-side lock held
150  * @obj: the reservation object
151  *
152  * Returns the exclusive fence (if any).  Does NOT take a
153  * reference.  The obj->lock must be held.
154  *
155  * RETURNS
156  * The exclusive fence or NULL
157  */
158 static inline struct fence *
159 reservation_object_get_excl(struct reservation_object *obj)
160 {
161 	return rcu_dereference_protected(obj->fence_excl,
162 					 reservation_object_held(obj));
163 }
164 
165 /**
166  * reservation_object_get_excl_rcu - get the reservation object's
167  * exclusive fence, without lock held.
168  * @obj: the reservation object
169  *
170  * If there is an exclusive fence, this atomically increments it's
171  * reference count and returns it.
172  *
173  * RETURNS
174  * The exclusive fence or NULL if none
175  */
176 static inline struct fence *
177 reservation_object_get_excl_rcu(struct reservation_object *obj)
178 {
179 	struct fence *fence;
180 	unsigned seq;
181 retry:
182 	seq = read_seqcount_begin(&obj->seq);
183 	rcu_read_lock();
184 	fence = rcu_dereference(obj->fence_excl);
185 	if (read_seqcount_retry(&obj->seq, seq)) {
186 		rcu_read_unlock();
187 		goto retry;
188 	}
189 	fence = fence_get(fence);
190 	rcu_read_unlock();
191 	return fence;
192 }
193 
194 int reservation_object_reserve_shared(struct reservation_object *obj);
195 void reservation_object_add_shared_fence(struct reservation_object *obj,
196 					 struct fence *fence);
197 
198 void reservation_object_add_excl_fence(struct reservation_object *obj,
199 				       struct fence *fence);
200 
201 int reservation_object_get_fences_rcu(struct reservation_object *obj,
202 				      struct fence **pfence_excl,
203 				      unsigned *pshared_count,
204 				      struct fence ***pshared);
205 
206 long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
207 					 bool wait_all, bool intr,
208 					 unsigned long timeout);
209 
210 bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
211 					  bool test_all);
212 
213 #endif /* _LINUX_RESERVATION_H */
214