2 This file is part of PulseAudio.
4 Copyright 2006 Lennart Poettering
6 PulseAudio is free software; you can redistribute it and/or modify
7 it under the terms of the GNU Lesser General Public License as
8 published by the Free Software Foundation; either version 2.1 of the
9 License, or (at your option) any later version.
11 PulseAudio is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public
17 License along with PulseAudio; if not, see <http://www.gnu.org/licenses/>.
27 #include <pulsecore/atomic.h>
28 #include <pulsecore/log.h>
29 #include <pulsecore/thread.h>
30 #include <pulsecore/macro.h>
31 #include <pulsecore/core-util.h>
32 #include <pulse/xmalloc.h>
36 /* For debugging purposes we can define _Y to put and extra thread
37 * yield between each operation. */
42 #define _Y pa_thread_yield()
44 #define _Y do { } while(0)
48 pa_fdsem *read_fdsem, *write_fdsem;
49 pa_shmasyncq_data *data;
52 static int is_power_of_two(unsigned size) {
53 return !(size & (size - 1));
56 static int reduce(pa_shmasyncq *l, int value) {
57 return value & (unsigned) (l->n_elements - 1);
60 static pa_atomic_t* get_cell(pa_shmasyncq *l, unsigned i) {
61 pa_assert(i < l->data->n_elements);
63 return (pa_atomic_t*) ((uint8*t) l->data + PA_ALIGN(sizeof(pa_shmasyncq_data)) + i * (PA_ALIGN(sizeof(pa_atomic_t)) + PA_ALIGN(element_size)))
66 static void *get_cell_data(pa_atomic_t *a) {
67 return (uint8_t*) a + PA_ALIGN(sizeof(atomic_t));
70 pa_shmasyncq *pa_shmasyncq_new(unsigned n_elements, size_t element_size, void *data, int fd[2]) {
73 pa_assert(n_elements > 0);
74 pa_assert(is_power_of_two(n_elements));
75 pa_assert(element_size > 0);
79 l = pa_xnew(pa_shmasyncq, 1);
82 memset(data, 0, PA_SHMASYNCQ_SIZE(n_elements, element_size));
84 l->data->n_elements = n_elements;
85 l->data->element_size = element_size;
87 if (!(l->read_fdsem = pa_fdsem_new_shm(&d->read_fdsem_data))) {
91 fd[0] = pa_fdsem_get(l->read_fdsem);
93 if (!(l->write_fdsem = pa_fdsem_new(&d->write_fdsem_data, &fd[1]))) {
94 pa_fdsem_free(l->read_fdsem);
102 void pa_shmasyncq_free(pa_shmasyncq *l, pa_free_cb_t free_cb) {
108 while ((p = pa_shmasyncq_pop(l, 0)))
112 pa_fdsem_free(l->read_fdsem);
113 pa_fdsem_free(l->write_fdsem);
117 int pa_shmasyncq_push(pa_shmasyncq*l, void *p, int wait) {
119 pa_atomic_ptr_t *cells;
124 cells = PA_SHMASYNCQ_CELLS(l);
127 idx = reduce(l, l->write_idx);
129 if (!pa_atomic_ptr_cmpxchg(&cells[idx], NULL, p)) {
134 /* pa_log("sleeping on push"); */
137 pa_fdsem_wait(l->read_fdsem);
138 } while (!pa_atomic_ptr_cmpxchg(&cells[idx], NULL, p));
144 pa_fdsem_post(l->write_fdsem);
149 void* pa_shmasyncq_pop(pa_shmasyncq*l, int wait) {
152 pa_atomic_ptr_t *cells;
156 cells = PA_SHMASYNCQ_CELLS(l);
159 idx = reduce(l, l->read_idx);
161 if (!(ret = pa_atomic_ptr_load(&cells[idx]))) {
166 /* pa_log("sleeping on pop"); */
169 pa_fdsem_wait(l->write_fdsem);
170 } while (!(ret = pa_atomic_ptr_load(&cells[idx])));
175 /* Guaranteed to succeed if we only have a single reader */
176 pa_assert_se(pa_atomic_ptr_cmpxchg(&cells[idx], ret, NULL));
181 pa_fdsem_post(l->read_fdsem);
186 int pa_shmasyncq_get_fd(pa_shmasyncq *q) {
189 return pa_fdsem_get(q->write_fdsem);
192 int pa_shmasyncq_before_poll(pa_shmasyncq *l) {
194 pa_atomic_ptr_t *cells;
198 cells = PA_SHMASYNCQ_CELLS(l);
201 idx = reduce(l, l->read_idx);
204 if (pa_atomic_ptr_load(&cells[idx]))
207 if (pa_fdsem_before_poll(l->write_fdsem) >= 0)
214 void pa_shmasyncq_after_poll(pa_shmasyncq *l) {
217 pa_fdsem_after_poll(l->write_fdsem);