int pa_fdsem_before_poll(pa_fdsem *f) {
pa_assert(f);
flush(f);
if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0))
return -1;
pa_atomic_inc(&f->data->waiting);
if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0)) {
pa_assert_se(pa_atomic_dec(&f->data->waiting) >= 1);
return -1;
}
return 0;
}
void pa_fdsem_wait(pa_fdsem *f) {
pa_assert(f);
flush(f);
if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0))
return;
pa_atomic_inc(&f->data->waiting);
while (!pa_atomic_cmpxchg(&f->data->signalled, 1, 0)) {
char x[10];
ssize_t r;
#ifdef HAVE_SYS_EVENTFD_H
if (f->efd >= 0) {
uint64_t u;
if ((r = pa_read(f->efd, &u, sizeof(u), NULL)) != sizeof(u)) {
if (r >= 0 || errno != EINTR) {
pa_log_error("Invalid read from eventfd: %s", r < 0 ? pa_cstrerror(errno) : "EOF");
pa_assert_not_reached();
}
continue;
}
r = (ssize_t) u;
} else
#endif
if ((r = pa_read(f->fds[0], &x, sizeof(x), NULL)) <= 0) {
if (r >= 0 || errno != EINTR) {
pa_log_error("Invalid read from pipe: %s", r < 0 ? pa_cstrerror(errno) : "EOF");
pa_assert_not_reached();
}
continue;
}
pa_atomic_sub(&f->data->in_pipe, (int) r);
}
pa_assert_se(pa_atomic_dec(&f->data->waiting) >= 1);
}
int pa_fdsem_try(pa_fdsem *f) {
pa_assert(f);
flush(f);
if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0))
return 1;
return 0;
}
int pa_fdsem_after_poll(pa_fdsem *f) {
pa_assert(f);
pa_assert_se(pa_atomic_dec(&f->data->waiting) >= 1);
flush(f);
if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0))
return 1;
return 0;
}
/* Lock free push to linked list stack */
static void stack_push(pa_flist *flist, pa_atomic_t *list, pa_flist_elem *new_elem) {
int tag, newindex, next;
pa_assert(list);
tag = pa_atomic_inc(&flist->current_tag);
newindex = new_elem - flist->table;
pa_assert(newindex >= 0 && newindex < (int) flist->size);
newindex |= (tag << flist->tag_shift) & flist->tag_mask;
do {
next = pa_atomic_load(list);
pa_atomic_store(&new_elem->next, next);
} while (!pa_atomic_cmpxchg(list, next, newindex));
}
/* Lock free pop from linked list stack */
static pa_flist_elem *stack_pop(pa_flist *flist, pa_atomic_t *list) {
pa_flist_elem *popped;
int idx;
pa_assert(list);
do {
idx = pa_atomic_load(list);
if (idx < 0)
return NULL;
popped = &flist->table[idx & flist->index_mask];
} while (!pa_atomic_cmpxchg(list, idx, pa_atomic_load(&popped->next)));
return popped;
}
unsigned pa_aupdate_write_swap(pa_aupdate *a) {
unsigned n;
pa_assert(a);
for (;;) {
n = (unsigned) pa_atomic_load(&a->read_lock);
/* If the read counter is > 0 wait; if it is 0 try to swap the lists */
if (COUNTER(n) > 0)
pa_semaphore_wait(a->semaphore);
else if (pa_atomic_cmpxchg(&a->read_lock, (int) n, (int) (n ^ MSB)))
break;
}
a->swapped = true;
return WHICH(n);
}
void pa_fdsem_post(pa_fdsem *f) {
pa_assert(f);
if (pa_atomic_cmpxchg(&f->data->signalled, 0, 1)) {
if (pa_atomic_load(&f->data->waiting)) {
ssize_t r;
char x = 'x';
pa_atomic_inc(&f->data->in_pipe);
for (;;) {
#ifdef HAVE_SYS_EVENTFD_H
if (f->efd >= 0) {
uint64_t u = 1;
if ((r = pa_write(f->efd, &u, sizeof(u), NULL)) != sizeof(u)) {
if (r >= 0 || errno != EINTR) {
pa_log_error("Invalid write to eventfd: %s", r < 0 ? pa_cstrerror(errno) : "EOF");
pa_assert_not_reached();
}
continue;
}
} else
#endif
if ((r = pa_write(f->fds[1], &x, 1, NULL)) != 1) {
if (r >= 0 || errno != EINTR) {
pa_log_error("Invalid write to pipe: %s", r < 0 ? pa_cstrerror(errno) : "EOF");
pa_assert_not_reached();
}
continue;
}
break;
}
}
}
}
