/* $Id$ */ /*** This file is part of PulseAudio. Copyright 2006 Lennart Poettering PulseAudio is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. PulseAudio is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with PulseAudio; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. ***/ #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include #include #include #include #include "asyncq.h" #define ASYNCQ_SIZE 128 /* For debugging purposes we can define _Y to put and extra thread * yield between each operation. */ #ifdef PROFILE #define _Y pa_thread_yield() #else #define _Y do { } while(0) #endif struct pa_asyncq { unsigned size; unsigned read_idx; unsigned write_idx; pa_atomic_t read_waiting; /* a bool */ pa_atomic_t write_waiting; /* a bool */ int read_fds[2], write_fds[2]; pa_atomic_t in_read_fifo, in_write_fifo; }; #define PA_ASYNCQ_CELLS(x) ((pa_atomic_ptr_t*) ((uint8_t*) (x) + PA_ALIGN(sizeof(struct pa_asyncq)))) static int is_power_of_two(unsigned size) { return !(size & (size - 1)); } static int reduce(pa_asyncq *l, int value) { return value & (unsigned) (l->size - 1); } pa_asyncq *pa_asyncq_new(unsigned size) { pa_asyncq *l; if (!size) size = ASYNCQ_SIZE; pa_assert(is_power_of_two(size)); l = pa_xmalloc0(PA_ALIGN(sizeof(pa_asyncq)) + (sizeof(pa_atomic_ptr_t) * size)); l->size = size; pa_atomic_store(&l->read_waiting, 0); pa_atomic_store(&l->write_waiting, 0); pa_atomic_store(&l->in_read_fifo, 0); pa_atomic_store(&l->in_write_fifo, 0); if (pipe(l->read_fds) < 0) { pa_xfree(l); return NULL; } if (pipe(l->write_fds) < 0) { pa_close(l->read_fds[0]); pa_close(l->read_fds[1]); pa_xfree(l); return NULL; } pa_make_nonblock_fd(l->read_fds[1]); pa_make_nonblock_fd(l->write_fds[1]); return l; } void pa_asyncq_free(pa_asyncq *l, pa_free_cb_t free_cb) { pa_assert(l); if (free_cb) { void *p; while ((p = pa_asyncq_pop(l, 0))) free_cb(p); } pa_close(l->read_fds[0]); pa_close(l->read_fds[1]); pa_close(l->write_fds[0]); pa_close(l->write_fds[1]); pa_xfree(l); } int pa_asyncq_push(pa_asyncq*l, void *p, int wait) { int idx; pa_atomic_ptr_t *cells; pa_assert(l); pa_assert(p); cells = PA_ASYNCQ_CELLS(l); _Y; idx = reduce(l, l->write_idx); if (!pa_atomic_ptr_cmpxchg(&cells[idx], NULL, p)) { /* Let's empty the FIFO from old notifications, before we return */ while (pa_atomic_load(&l->in_write_fifo) > 0) { ssize_t r; int x[20]; if ((r = read(l->write_fds[0], x, sizeof(x))) < 0) { if (errno == EINTR) continue; return -1; } pa_assert(r > 0); if (pa_atomic_sub(&l->in_write_fifo, r) <= r) break; } /* Now let's make sure that we didn't lose any events */ if (!pa_atomic_ptr_cmpxchg(&cells[idx], NULL, p)) { if (!wait) return -1; /* Let's wait for changes. */ _Y; pa_assert_se(pa_atomic_cmpxchg(&l->write_waiting, 0, 1)); for (;;) { char x[20]; ssize_t r; _Y; if (pa_atomic_ptr_cmpxchg(&cells[idx], NULL, p)) break; _Y; if ((r = read(l->write_fds[0], x, sizeof(x))) < 0) { if (errno == EINTR) continue; pa_assert_se(pa_atomic_cmpxchg(&l->write_waiting, 1, 0)); return -1; } pa_assert(r > 0); pa_atomic_sub(&l->in_write_fifo, r); } _Y; pa_assert_se(pa_atomic_cmpxchg(&l->write_waiting, 1, 0)); } } _Y; l->write_idx++; if (pa_atomic_load(&l->read_waiting) > 0) { char x = 'x'; _Y; if (write(l->read_fds[1], &x, sizeof(x)) > 0) { pa_atomic_inc(&l->in_read_fifo); /* pa_log("increasing %p by 1", l); */ } } return 0; } void* pa_asyncq_pop(pa_asyncq*l, int wait) { int idx; void *ret; pa_atomic_ptr_t *cells; pa_assert(l); cells = PA_ASYNCQ_CELLS(l); _Y; idx = reduce(l, l->read_idx); if (!(ret = pa_atomic_ptr_load(&cells[idx]))) { /* pa_log("pop failed wait=%i", wait); */ /* Hmm, nothing, here, so let's drop all queued events. */ while (pa_atomic_load(&l->in_read_fifo) > 0) { ssize_t r; int x[20]; if ((r = read(l->read_fds[0], x, sizeof(x))) < 0) { if (errno == EINTR) continue; return NULL; } pa_assert(r > 0); /* pa_log("decreasing %p by %i", l, r); */ if (pa_atomic_sub(&l->in_read_fifo, r) <= r) break; } /* Now let's make sure that we didn't lose any events */ if (!(ret = pa_atomic_ptr_load(&cells[idx]))) { if (!wait) return NULL; /* Let's wait for changes. */ _Y; pa_assert_se(pa_atomic_cmpxchg(&l->read_waiting, 0, 1)); for (;;) { char x[20]; ssize_t r; _Y; if ((ret = pa_atomic_ptr_load(&cells[idx]))) break; _Y; if ((r = read(l->read_fds[0], x, sizeof(x))) < 0) { if (errno == EINTR) continue; pa_assert_se(pa_atomic_cmpxchg(&l->read_waiting, 1, 0)); return NULL; } /* pa_log("decreasing %p by %i", l, r); */ pa_assert(r > 0); pa_atomic_sub(&l->in_read_fifo, r); } _Y; pa_assert_se(pa_atomic_cmpxchg(&l->read_waiting, 1, 0)); } } pa_assert(ret); /* Guaranteed if we only have a single reader */ pa_assert_se(pa_atomic_ptr_cmpxchg(&cells[idx], ret, NULL)); _Y; l->read_idx++; if (pa_atomic_load(&l->write_waiting) > 0) { char x = 'x'; _Y; if (write(l->write_fds[1], &x, sizeof(x)) >= 0) pa_atomic_inc(&l->in_write_fifo); } return ret; } int pa_asyncq_get_fd(pa_asyncq *q) { pa_assert(q); return q->read_fds[0]; } int pa_asyncq_before_poll(pa_asyncq *l) { int idx; pa_atomic_ptr_t *cells; pa_assert(l); cells = PA_ASYNCQ_CELLS(l); _Y; idx = reduce(l, l->read_idx); if (pa_atomic_ptr_load(&cells[idx]) || pa_atomic_load(&l->in_read_fifo) > 0) return -1; pa_assert_se(pa_atomic_cmpxchg(&l->read_waiting, 0, 1)); if (pa_atomic_ptr_load(&cells[idx]) || pa_atomic_load(&l->in_read_fifo) > 0) { pa_assert_se(pa_atomic_cmpxchg(&l->read_waiting, 1, 0)); return -1; } return 0; } void pa_asyncq_after_poll(pa_asyncq *l) { pa_assert(l); pa_assert_se(pa_atomic_cmpxchg(&l->read_waiting, 1, 0)); }