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68cc36140b
supresses a warning when compiling with NDEBUG:
pulsecore/aupdate.c: In function 'pa_aupdate_read_end':
pulsecore/aupdate.c:82:14: warning: variable 'n' set but not used [-Wunused-but-set-variable]
unsigned n;
pulsecore/sink-input.c: In function 'pa_sink_input_unlink':
pulsecore/sink-input.c:648:27: warning: variable 'p' set but not used [-Wunused-but-set-variable]
pa_source_output *o, *p = NULL;
pulsecore/sink-input.c: In function 'find_filter_sink_input':
pulsecore/sink-input.c:1523:14: warning: unused variable 'i' [-Wunused-variable]
unsigned i = 0;
pulsecore/sink-input.c: In function 'pa_sink_input_start_move':
pulsecore/sink-input.c:1569:27: warning: variable 'p' set but not used [-Wunused-but-set-variable]
pa_source_output *o, *p = NULL;
CC pulsecore/libpulsecore_5.0_la-sink.lo
pulsecore/sink.c: In function 'pa_sink_unlink':
pulsecore/sink.c:673:24: warning: variable 'j' set but not used [-Wunused-but-set-variable]
pa_sink_input *i, *j = NULL;
pulsecore/source-output.c: In function 'find_filter_source_output':
pulsecore/source-output.c:1179:9: warning: unused variable 'i' [-Wunused-variable]
int i = 0;
CC pulsecore/libpulsecore_5.0_la-source.lo
pulsecore/source.c: In function 'pa_source_unlink':
pulsecore/source.c:616:27: warning: variable 'j' set but not used [-Wunused-but-set-variable]
pa_source_output *o, *j = NULL;
Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
137 lines
3.1 KiB
C
137 lines
3.1 KiB
C
/***
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This file is part of PulseAudio.
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Copyright 2009 Lennart Poettering
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PulseAudio is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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PulseAudio is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with PulseAudio; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
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USA.
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***/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif
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#include <pulse/xmalloc.h>
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#include <pulsecore/semaphore.h>
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#include <pulsecore/macro.h>
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#include <pulsecore/mutex.h>
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#include "aupdate.h"
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#define MSB (1U << (sizeof(unsigned)*8U-1))
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#define WHICH(n) (!!((n) & MSB))
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#define COUNTER(n) ((n) & ~MSB)
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struct pa_aupdate {
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pa_atomic_t read_lock;
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pa_mutex *write_lock;
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pa_semaphore *semaphore;
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bool swapped;
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};
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pa_aupdate *pa_aupdate_new(void) {
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pa_aupdate *a;
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a = pa_xnew(pa_aupdate, 1);
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pa_atomic_store(&a->read_lock, 0);
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a->write_lock = pa_mutex_new(false, false);
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a->semaphore = pa_semaphore_new(0);
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return a;
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}
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void pa_aupdate_free(pa_aupdate *a) {
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pa_assert(a);
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pa_mutex_free(a->write_lock);
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pa_semaphore_free(a->semaphore);
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pa_xfree(a);
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}
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unsigned pa_aupdate_read_begin(pa_aupdate *a) {
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unsigned n;
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pa_assert(a);
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/* Increase the lock counter */
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n = (unsigned) pa_atomic_inc(&a->read_lock);
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/* When n is 0 we have about 2^31 threads running that all try to
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* access the data at the same time, oh my! */
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pa_assert(COUNTER(n)+1 > 0);
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/* The uppermost bit tells us which data to look at */
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return WHICH(n);
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}
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void pa_aupdate_read_end(pa_aupdate *a) {
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unsigned PA_UNUSED n;
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pa_assert(a);
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/* Decrease the lock counter */
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n = (unsigned) pa_atomic_dec(&a->read_lock);
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/* Make sure the counter was valid */
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pa_assert(COUNTER(n) > 0);
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/* Post the semaphore */
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pa_semaphore_post(a->semaphore);
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}
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unsigned pa_aupdate_write_begin(pa_aupdate *a) {
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unsigned n;
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pa_assert(a);
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pa_mutex_lock(a->write_lock);
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n = (unsigned) pa_atomic_load(&a->read_lock);
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a->swapped = false;
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return !WHICH(n);
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}
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unsigned pa_aupdate_write_swap(pa_aupdate *a) {
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unsigned n;
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pa_assert(a);
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for (;;) {
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n = (unsigned) pa_atomic_load(&a->read_lock);
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/* If the read counter is > 0 wait; if it is 0 try to swap the lists */
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if (COUNTER(n) > 0)
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pa_semaphore_wait(a->semaphore);
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else if (pa_atomic_cmpxchg(&a->read_lock, (int) n, (int) (n ^ MSB)))
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break;
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}
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a->swapped = true;
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return WHICH(n);
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}
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void pa_aupdate_write_end(pa_aupdate *a) {
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pa_assert(a);
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if (!a->swapped)
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pa_aupdate_write_swap(a);
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pa_mutex_unlock(a->write_lock);
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}
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