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/***
This file is part of PulseAudio.
Copyright 2006-2008 Lennart Poettering
Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
Copyright (C) 2012 Canonical Ltd.
Contact: Jyri Sarha <Jyri.Sarha@nokia.com>
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, see <http://www.gnu.org/licenses/>.
***/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <pulse/xmalloc.h>
#include <pulsecore/atomic.h>
#include <pulsecore/log.h>
#include <pulsecore/macro.h>
#include <pulsecore/core-util.h>
#include <pulsecore/macro.h>
#include "flist.h"
#define FLIST_SIZE 256
/* Atomic table indices contain
sign bit = if set, indicates empty/NULL value
tag bits (to avoid the ABA problem)
actual index bits
*/
/* Lock free single linked list element. */
struct pa_flist_elem {
pa_atomic_t next;
pa_atomic_ptr_t ptr;
};
typedef struct pa_flist_elem pa_flist_elem;
struct pa_flist {
char *name;
unsigned size;
pa_atomic_t current_tag;
int index_mask;
int tag_shift;
int tag_mask;
/* Stack that contains pointers stored into free list */
pa_atomic_t stored;
/* Stack that contains empty list elements */
pa_atomic_t empty;
pa_flist_elem table[];
};
/* 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;
}
/* 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));
}
pa_flist *pa_flist_new_with_name(unsigned size, const char *name) {
pa_flist *l;
unsigned i;
pa_assert(name);
if (!size)
size = FLIST_SIZE;
l = pa_xmalloc0(sizeof(pa_flist) + sizeof(pa_flist_elem) * size);
l->name = pa_xstrdup(name);
l->size = size;
while (1 << l->tag_shift < (int) size)
l->tag_shift++;
l->index_mask = (1 << l->tag_shift) - 1;
l->tag_mask = INT_MAX - l->index_mask;
pa_atomic_store(&l->stored, -1);
pa_atomic_store(&l->empty, -1);
for (i=0; i < size; i++) {
stack_push(l, &l->empty, &l->table[i]);
}
return l;
}
pa_flist *pa_flist_new(unsigned size) {
return pa_flist_new_with_name(size, "unknown");
}
void pa_flist_free(pa_flist *l, pa_free_cb_t free_cb) {
pa_assert(l);
pa_assert(l->name);
if (free_cb) {
pa_flist_elem *elem;
while((elem = stack_pop(l, &l->stored)))
free_cb(pa_atomic_ptr_load(&elem->ptr));
}
pa_xfree(l->name);
pa_xfree(l);
}
int pa_flist_push(pa_flist *l, void *p) {
pa_flist_elem *elem;
pa_assert(l);
pa_assert(p);
elem = stack_pop(l, &l->empty);
if (elem == NULL) {
if (pa_log_ratelimit(PA_LOG_DEBUG))
pa_log_debug("%s flist is full (don't worry)", l->name);
return -1;
}
pa_atomic_ptr_store(&elem->ptr, p);
stack_push(l, &l->stored, elem);
return 0;
}
void* pa_flist_pop(pa_flist *l) {
pa_flist_elem *elem;
void *ptr;
pa_assert(l);
elem = stack_pop(l, &l->stored);
if (elem == NULL)
return NULL;
ptr = pa_atomic_ptr_load(&elem->ptr);
stack_push(l, &l->empty, elem);
return ptr;
}
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