mirror of
https://gitlab.freedesktop.org/pulseaudio/pulseaudio.git
synced 2025-11-08 13:29:59 -05:00
5effc83479
FSF addresses used in PA sources are no longer valid and rpmlint generates numerous warnings during packaging because of this. This patch changes all FSF addresses to FSF web page according to the GPL how-to: https://www.gnu.org/licenses/gpl-howto.en.html Done automatically by sed-ing through sources.
135 lines
3 KiB
C
135 lines
3 KiB
C
/***
|
|
This file is part of PulseAudio.
|
|
|
|
Copyright 2009 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
|
|
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/semaphore.h>
|
|
#include <pulsecore/macro.h>
|
|
#include <pulsecore/mutex.h>
|
|
|
|
#include "aupdate.h"
|
|
|
|
#define MSB (1U << (sizeof(unsigned)*8U-1))
|
|
#define WHICH(n) (!!((n) & MSB))
|
|
#define COUNTER(n) ((n) & ~MSB)
|
|
|
|
struct pa_aupdate {
|
|
pa_atomic_t read_lock;
|
|
pa_mutex *write_lock;
|
|
pa_semaphore *semaphore;
|
|
bool swapped;
|
|
};
|
|
|
|
pa_aupdate *pa_aupdate_new(void) {
|
|
pa_aupdate *a;
|
|
|
|
a = pa_xnew(pa_aupdate, 1);
|
|
pa_atomic_store(&a->read_lock, 0);
|
|
a->write_lock = pa_mutex_new(false, false);
|
|
a->semaphore = pa_semaphore_new(0);
|
|
|
|
return a;
|
|
}
|
|
|
|
void pa_aupdate_free(pa_aupdate *a) {
|
|
pa_assert(a);
|
|
|
|
pa_mutex_free(a->write_lock);
|
|
pa_semaphore_free(a->semaphore);
|
|
|
|
pa_xfree(a);
|
|
}
|
|
|
|
unsigned pa_aupdate_read_begin(pa_aupdate *a) {
|
|
unsigned n;
|
|
|
|
pa_assert(a);
|
|
|
|
/* Increase the lock counter */
|
|
n = (unsigned) pa_atomic_inc(&a->read_lock);
|
|
|
|
/* When n is 0 we have about 2^31 threads running that all try to
|
|
* access the data at the same time, oh my! */
|
|
pa_assert(COUNTER(n)+1 > 0);
|
|
|
|
/* The uppermost bit tells us which data to look at */
|
|
return WHICH(n);
|
|
}
|
|
|
|
void pa_aupdate_read_end(pa_aupdate *a) {
|
|
unsigned PA_UNUSED n;
|
|
|
|
pa_assert(a);
|
|
|
|
/* Decrease the lock counter */
|
|
n = (unsigned) pa_atomic_dec(&a->read_lock);
|
|
|
|
/* Make sure the counter was valid */
|
|
pa_assert(COUNTER(n) > 0);
|
|
|
|
/* Post the semaphore */
|
|
pa_semaphore_post(a->semaphore);
|
|
}
|
|
|
|
unsigned pa_aupdate_write_begin(pa_aupdate *a) {
|
|
unsigned n;
|
|
|
|
pa_assert(a);
|
|
|
|
pa_mutex_lock(a->write_lock);
|
|
|
|
n = (unsigned) pa_atomic_load(&a->read_lock);
|
|
|
|
a->swapped = false;
|
|
|
|
return !WHICH(n);
|
|
}
|
|
|
|
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_aupdate_write_end(pa_aupdate *a) {
|
|
pa_assert(a);
|
|
|
|
if (!a->swapped)
|
|
pa_aupdate_write_swap(a);
|
|
|
|
pa_mutex_unlock(a->write_lock);
|
|
}
|