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/*
* messagebuffer.c -- realtime-safe message handling for jackd.
*
* This interface is included in libjack so backend drivers can use
* it, *not* for external client processes. It implements the
* VERBOSE() and MESSAGE() macros in a realtime-safe manner.
*/
/*
* Copyright (C) 2004 Rui Nuno Capela, Steve Harris
*
* This program 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.
*
* This program 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 this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
*/
#include <unistd.h>
#include <string.h>
#include <pthread.h>
#include <stdarg.h>
#include <stdio.h>
#include "messagebuffer.h"
#include "atomicity.h"
#include "internal.h"
/* MB_NEXT() relies on the fact that MB_BUFFERS is a power of two */
#define MB_BUFFERS 128
#define MB_NEXT(index) ((index + 1) & (MB_BUFFERS - 1))
#define MB_BUFFERSIZE 256 /* message length limit */
static char mb_buffers[MB_BUFFERS][MB_BUFFERSIZE];
static volatile unsigned int mb_initialized = 0;
static volatile unsigned int mb_inbuffer = 0;
static volatile unsigned int mb_outbuffer = 0;
static volatile _Atomic_word mb_overruns = 0;
static pthread_t mb_writer_thread;
static pthread_mutex_t mb_write_lock;
static pthread_cond_t mb_ready_cond;
static void (*mb_thread_init_callback)(void*) = 0;
static void* mb_thread_init_callback_arg = 0;
static void
mb_flush ()
{
/* called WITHOUT the mb_write_lock */
while (mb_outbuffer != mb_inbuffer) {
jack_info (mb_buffers[mb_outbuffer]);
mb_outbuffer = MB_NEXT (mb_outbuffer);
}
}
static void *
mb_thread_func (void *arg)
{
/* The mutex is only to eliminate collisions between multiple
* writer threads and protect the condition variable. */
pthread_mutex_lock (&mb_write_lock);
while (mb_initialized) {
pthread_cond_wait (&mb_ready_cond, &mb_write_lock);
if (mb_thread_init_callback) {
/* the client asked for all threads to run a thread
initialization callback, which includes us.
*/
mb_thread_init_callback (mb_thread_init_callback_arg);
mb_thread_init_callback = 0;
/* note that we've done it */
pthread_cond_signal (&mb_ready_cond);
}
/* releasing the mutex reduces contention */
pthread_mutex_unlock (&mb_write_lock);
mb_flush ();
pthread_mutex_lock (&mb_write_lock);
}
pthread_mutex_unlock (&mb_write_lock);
return NULL;
}
void
jack_messagebuffer_init ()
{
if (mb_initialized) {
return;
}
pthread_mutex_init (&mb_write_lock, NULL);
pthread_cond_init (&mb_ready_cond, NULL);
mb_overruns = 0;
mb_initialized = 1;
if (jack_thread_creator (&mb_writer_thread, NULL, &mb_thread_func, NULL) != 0) {
mb_initialized = 0;
}
}
void
jack_messagebuffer_exit ()
{
if (!mb_initialized) {
return;
}
pthread_mutex_lock (&mb_write_lock);
mb_initialized = 0;
pthread_cond_signal (&mb_ready_cond);
pthread_mutex_unlock (&mb_write_lock);
pthread_join (mb_writer_thread, NULL);
mb_flush ();
if (mb_overruns) {
jack_error ("WARNING: %d message buffer overruns!",
mb_overruns);
}
pthread_mutex_destroy (&mb_write_lock);
pthread_cond_destroy (&mb_ready_cond);
}
void
jack_messagebuffer_add (const char *fmt, ...)
{
char msg[MB_BUFFERSIZE];
va_list ap;
/* format the message first, to reduce lock contention */
va_start (ap, fmt);
vsnprintf (msg, MB_BUFFERSIZE, fmt, ap);
va_end (ap);
if (!mb_initialized) {
/* Unable to print message with realtime safety.
* Complain and print it anyway. */
fprintf (stderr, "ERROR: messagebuffer not initialized: %s",
msg);
return;
}
if (pthread_mutex_trylock (&mb_write_lock) == 0) {
strncpy (mb_buffers[mb_inbuffer], msg, MB_BUFFERSIZE);
mb_inbuffer = MB_NEXT (mb_inbuffer);
pthread_cond_signal (&mb_ready_cond);
pthread_mutex_unlock (&mb_write_lock);
} else { /* lock collision */
exchange_and_add (&mb_overruns, 1);
}
}
void
jack_messagebuffer_thread_init (void (*cb)(void*), void* arg)
{
pthread_mutex_lock (&mb_write_lock);
/* set up the callback */
mb_thread_init_callback_arg = arg;
mb_thread_init_callback = cb;
/* wake msg buffer thread */
pthread_cond_signal (&mb_ready_cond);
/* wait for it to be done */
pthread_cond_wait (&mb_ready_cond, &mb_write_lock);
/* and we're done */
pthread_mutex_unlock (&mb_write_lock);
}
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