1 /**************************************************************************
2 *
3 * Copyright 2009 VMware, Inc.
4 * All Rights Reserved.
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the
8 * "Software"), to deal in the Software without restriction, including
9 * without limitation the rights to use, copy, modify, merge, publish,
10 * distribute, sub license, and/or sell copies of the Software, and to
11 * permit persons to whom the Software is furnished to do so, subject to
12 * the following conditions:
13 *
14 * The above copyright notice and this permission notice (including the
15 * next paragraph) shall be included in all copies or substantial portions
16 * of the Software.
17 *
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
19 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
20 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
21 * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
22 * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
23 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
24 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
25 *
26 **************************************************************************/
27
28
29 /**
30 * Scene queue. We'll use two queues. One contains "full" scenes which
31 * are produced by the "setup" code. The other contains "empty" scenes
32 * which are produced by the "rast" code when it finishes rendering a scene.
33 */
34
35 #include "os/os_thread.h"
36 #include "util/u_memory.h"
37 #include "lp_scene_queue.h"
38 #include "util/u_math.h"
39
40
41
42 #define SCENE_QUEUE_SIZE 4
43
44
45
46 /**
47 * A queue of scenes
48 */
49 struct lp_scene_queue
50 {
51 struct lp_scene *scenes[SCENE_QUEUE_SIZE];
52
53 mtx_t mutex;
54 cnd_t change;
55
56 /* These values wrap around, so that head == tail means empty. When used
57 * to index the array, we use them modulo the queue size. This scheme
58 * works because the queue size is a power of two.
59 */
60 unsigned head;
61 unsigned tail;
62 };
63
64
65
66 /** Allocate a new scene queue */
67 struct lp_scene_queue *
lp_scene_queue_create(void)68 lp_scene_queue_create(void)
69 {
70 /* Circular queue behavior depends on size being a power of two. */
71 STATIC_ASSERT(SCENE_QUEUE_SIZE > 0);
72 STATIC_ASSERT((SCENE_QUEUE_SIZE & (SCENE_QUEUE_SIZE - 1)) == 0);
73
74 struct lp_scene_queue *queue = CALLOC_STRUCT(lp_scene_queue);
75
76 if (!queue)
77 return NULL;
78
79 (void) mtx_init(&queue->mutex, mtx_plain);
80 cnd_init(&queue->change);
81
82 return queue;
83 }
84
85
86 /** Delete a scene queue */
87 void
lp_scene_queue_destroy(struct lp_scene_queue * queue)88 lp_scene_queue_destroy(struct lp_scene_queue *queue)
89 {
90 cnd_destroy(&queue->change);
91 mtx_destroy(&queue->mutex);
92 FREE(queue);
93 }
94
95
96 /** Remove first lp_scene from head of queue */
97 struct lp_scene *
lp_scene_dequeue(struct lp_scene_queue * queue,boolean wait)98 lp_scene_dequeue(struct lp_scene_queue *queue, boolean wait)
99 {
100 mtx_lock(&queue->mutex);
101
102 if (wait) {
103 /* Wait for queue to be not empty. */
104 while (queue->head == queue->tail)
105 cnd_wait(&queue->change, &queue->mutex);
106 } else {
107 if (queue->head == queue->tail) {
108 mtx_unlock(&queue->mutex);
109 return NULL;
110 }
111 }
112
113 struct lp_scene *scene = queue->scenes[queue->head++ % SCENE_QUEUE_SIZE];
114
115 cnd_signal(&queue->change);
116 mtx_unlock(&queue->mutex);
117
118 return scene;
119 }
120
121
122 /** Add an lp_scene to tail of queue */
123 void
lp_scene_enqueue(struct lp_scene_queue * queue,struct lp_scene * scene)124 lp_scene_enqueue(struct lp_scene_queue *queue, struct lp_scene *scene)
125 {
126 mtx_lock(&queue->mutex);
127
128 /* Wait for free space. */
129 while (queue->tail - queue->head >= SCENE_QUEUE_SIZE)
130 cnd_wait(&queue->change, &queue->mutex);
131
132 queue->scenes[queue->tail++ % SCENE_QUEUE_SIZE] = scene;
133
134 cnd_signal(&queue->change);
135 mtx_unlock(&queue->mutex);
136 }
137