mpv/stream/cache.c

744 lines
24 KiB
C

/*
* This file is part of MPlayer.
*
* MPlayer is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* MPlayer 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 General Public License along
* with MPlayer; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
// Time in seconds the main thread waits for the cache thread. On wakeups, the
// code checks for user requested aborts and also prints warnings that the
// cache is being slow.
#define CACHE_WAIT_TIME 0.5
// The time the cache sleeps in idle mode. This controls how often the cache
// retries reading from the stream after EOF has reached (in case the stream is
// actually readable again, for example if data has been appended to a file).
// Note that if this timeout is too low, the player will waste too much CPU
// when player is paused.
#define CACHE_IDLE_SLEEP_TIME 1.0
// Time in seconds the cache updates "cached" controls. Note that idle mode
// will block the cache from doing this, and this timeout is honored only if
// the cache is active.
#define CACHE_UPDATE_CONTROLS_TIME 2.0
// Time in seconds the cache prints a new message at all.
#define CACHE_NO_SPAM 5.0
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <errno.h>
#include <assert.h>
#include <pthread.h>
#include <time.h>
#include <sys/time.h>
#include <libavutil/common.h>
#include "config.h"
#include "osdep/timer.h"
#include "osdep/threads.h"
#include "common/msg.h"
#include "options/options.h"
#include "stream.h"
#include "common/common.h"
// Note: (struct priv*)(cache->priv)->cache == cache
struct priv {
pthread_t cache_thread;
bool cache_thread_running;
pthread_mutex_t mutex;
pthread_cond_t wakeup;
// Constants (as long as cache thread is running)
// Some of these might actually be changed by a synced cache resize.
unsigned char *buffer; // base pointer of the allocated buffer memory
int64_t buffer_size; // size of the allocated buffer memory
int64_t back_size; // keep back_size amount of old bytes for backward seek
int64_t seek_limit; // keep filling cache if distance is less that seek limit
struct byte_meta *bm; // additional per-byte metadata
bool seekable; // underlying stream is seekable
struct mp_log *log;
// Owned by the main thread
stream_t *cache; // wrapper stream, used by demuxer etc.
double last_warn_time;
// Owned by the cache thread
stream_t *stream; // "real" stream, used to read from the source media
// All the following members are shared between the threads.
// You must lock the mutex to access them.
// Ringbuffer
int64_t min_filepos; // range of file that is cached in the buffer
int64_t max_filepos; // ... max_filepos being the last read position
bool eof; // true if max_filepos = EOF
int64_t offset; // buffer[WRAP(s->max_filepos - offset)] corresponds
// to the byte at max_filepos (must be wrapped by
// buffer_size)
bool idle; // cache thread has stopped reading
int64_t reads; // number of actual read attempts performed
int64_t read_filepos; // client read position (mirrors cache->pos)
int control; // requested STREAM_CTRL_... or CACHE_CTRL_...
void *control_arg; // temporary for executing STREAM_CTRLs
int control_res;
bool control_flush;
// Cached STREAM_CTRLs
double stream_time_length;
double stream_start_time;
int64_t stream_size;
bool stream_manages_timeline;
unsigned int stream_num_chapters;
int stream_cache_idle;
int stream_cache_fill;
char **stream_metadata;
char *disc_name;
};
// Store additional per-byte metadata. Since per-byte would be way too
// inefficient, store it only for every BYTE_META_CHUNK_SIZE byte.
struct byte_meta {
float stream_pts;
};
enum {
BYTE_META_CHUNK_SIZE = 8 * 1024,
CACHE_INTERRUPTED = -1,
CACHE_CTRL_NONE = 0,
CACHE_CTRL_QUIT = -1,
CACHE_CTRL_PING = -2,
// we should fill buffer only if space>=FILL_LIMIT
FILL_LIMIT = FFMAX(16 * 1024, BYTE_META_CHUNK_SIZE * 2),
};
static int64_t mp_clipi64(int64_t val, int64_t min, int64_t max)
{
val = FFMIN(val, max);
val = FFMAX(val, min);
return val;
}
// Used by the main thread to wakeup the cache thread, and to wait for the
// cache thread. The cache mutex has to be locked when calling this function.
// *retry_time should be set to 0 on the first call.
// Returns CACHE_INTERRUPTED if the caller is supposed to abort.
static int cache_wakeup_and_wait(struct priv *s, double *retry_time)
{
if (stream_check_interrupt(s->cache))
return CACHE_INTERRUPTED;
double start = mp_time_sec();
if (!s->last_warn_time || start - s->last_warn_time >= CACHE_NO_SPAM) {
// Print a "more severe" warning after waiting 1 second and no new data
if ((*retry_time) >= 1.0) {
MP_ERR(s, "Cache keeps not responding.\n");
s->last_warn_time = start;
} else if (*retry_time > 0.1) {
MP_WARN(s, "Cache is not responding - slow/stuck network connection?\n");
s->last_warn_time = start;
}
}
pthread_cond_signal(&s->wakeup);
mpthread_cond_timedwait_rel(&s->wakeup, &s->mutex, CACHE_WAIT_TIME);
*retry_time += mp_time_sec() - start;
return 0;
}
// Runs in the cache thread
static void cache_drop_contents(struct priv *s)
{
s->offset = s->min_filepos = s->max_filepos = s->read_filepos;
s->eof = false;
}
// Copy at most dst_size from the cache at the given absolute file position pos.
// Return number of bytes that could actually be read.
// Does not advance the file position, or change anything else.
// Can be called from anywhere, as long as the mutex is held.
static size_t read_buffer(struct priv *s, unsigned char *dst,
size_t dst_size, int64_t pos)
{
size_t read = 0;
while (read < dst_size) {
if (pos >= s->max_filepos || pos < s->min_filepos)
break;
int64_t newb = s->max_filepos - pos; // new bytes in the buffer
int64_t bpos = pos - s->offset; // file pos to buffer memory pos
if (bpos < 0) {
bpos += s->buffer_size;
} else if (bpos >= s->buffer_size) {
bpos -= s->buffer_size;
}
if (newb > s->buffer_size - bpos)
newb = s->buffer_size - bpos; // handle wrap...
newb = MPMIN(newb, dst_size - read);
assert(newb >= 0 && read + newb <= dst_size);
assert(bpos >= 0 && bpos + newb <= s->buffer_size);
memcpy(&dst[read], &s->buffer[bpos], newb);
read += newb;
pos += newb;
}
return read;
}
// Runs in the cache thread.
// Returns true if reading was attempted, and the mutex was shortly unlocked.
static bool cache_fill(struct priv *s)
{
int64_t read = s->read_filepos;
int len = 0;
// drop cache contents only if seeking backward or too much fwd.
// This is also done for on-disk files, since it loses the backseek cache.
// That in turn can cause major bandwidth increase and performance
// issues with e.g. mov or badly interleaved files
if (read < s->min_filepos || read > s->max_filepos + s->seek_limit) {
MP_VERBOSE(s, "Dropping cache at pos %"PRId64", "
"cached range: %"PRId64"-%"PRId64".\n", read,
s->min_filepos, s->max_filepos);
cache_drop_contents(s);
}
if (stream_tell(s->stream) != s->max_filepos && s->seekable) {
MP_VERBOSE(s, "Seeking underlying stream: %"PRId64" -> %"PRId64"\n",
stream_tell(s->stream), s->max_filepos);
stream_seek(s->stream, s->max_filepos);
if (stream_tell(s->stream) != s->max_filepos)
goto done;
}
// number of buffer bytes which should be preserved in backwards direction
int64_t back = mp_clipi64(read - s->min_filepos, 0, s->back_size);
// number of buffer bytes that are valid and can be read
int64_t newb = FFMAX(s->max_filepos - read, 0);
// max. number of bytes that can be written (starting from max_filepos)
int64_t space = s->buffer_size - (newb + back);
// offset into the buffer that maps to max_filepos
int pos = s->max_filepos - s->offset;
if (pos >= s->buffer_size)
pos -= s->buffer_size; // wrap-around
if (space < FILL_LIMIT) {
s->idle = true;
s->reads++; // don't stuck main thread
return false;
}
// limit to end of buffer (without wrapping)
if (pos + space >= s->buffer_size)
space = s->buffer_size - pos;
// limit read size (or else would block and read the entire buffer in 1 call)
space = FFMIN(space, s->stream->read_chunk);
// back+newb+space <= buffer_size
int64_t back2 = s->buffer_size - (space + newb); // max back size
if (s->min_filepos < (read - back2))
s->min_filepos = read - back2;
// The read call might take a long time and block, so drop the lock.
pthread_mutex_unlock(&s->mutex);
len = stream_read_partial(s->stream, &s->buffer[pos], space);
pthread_mutex_lock(&s->mutex);
double pts;
if (stream_control(s->stream, STREAM_CTRL_GET_CURRENT_TIME, &pts) <= 0)
pts = MP_NOPTS_VALUE;
for (int64_t b_pos = pos; b_pos < pos + len + BYTE_META_CHUNK_SIZE;
b_pos += BYTE_META_CHUNK_SIZE)
{
s->bm[b_pos / BYTE_META_CHUNK_SIZE] = (struct byte_meta){.stream_pts = pts};
}
s->max_filepos += len;
if (pos + len == s->buffer_size)
s->offset += s->buffer_size; // wrap...
done:
s->eof = len <= 0;
s->idle = s->eof;
s->reads++;
if (s->eof)
MP_VERBOSE(s, "EOF reached.\n");
pthread_cond_signal(&s->wakeup);
return true;
}
// This is called both during init and at runtime.
static int resize_cache(struct priv *s, int64_t size)
{
int64_t min_size = FILL_LIMIT * 4;
int64_t max_size = ((size_t)-1) / 4;
int64_t buffer_size = MPMIN(MPMAX(size, min_size), max_size);
unsigned char *buffer = malloc(buffer_size);
struct byte_meta *bm = calloc(buffer_size / BYTE_META_CHUNK_SIZE + 2,
sizeof(struct byte_meta));
if (!buffer || !bm) {
free(buffer);
free(bm);
return STREAM_ERROR;
}
if (s->buffer) {
// Copy & free the old ringbuffer data.
// If the buffer is too small, prefer to copy these regions:
// 1. Data starting from read_filepos, until cache end
size_t read_1 = read_buffer(s, buffer, buffer_size, s->read_filepos);
// 2. then data from before read_filepos until cache start
// (this one needs to be copied to the end of the ringbuffer)
size_t read_2 = 0;
if (s->min_filepos < s->read_filepos) {
size_t copy_len = buffer_size - read_1;
copy_len = MPMIN(copy_len, s->read_filepos - s->min_filepos);
assert(copy_len + read_1 <= buffer_size);
read_2 = read_buffer(s, buffer + buffer_size - copy_len, copy_len,
s->read_filepos - copy_len);
// This shouldn't happen, unless copy_len was computed incorrectly.
assert(read_2 == copy_len);
}
// Set it up such that read_1 is at buffer pos 0, and read_2 wraps
// around below it, so that it is located at the end of the buffer.
s->min_filepos = s->read_filepos - read_2;
s->max_filepos = s->read_filepos + read_1;
s->offset = s->max_filepos - read_1;
} else {
cache_drop_contents(s);
}
free(s->buffer);
free(s->bm);
s->buffer_size = buffer_size;
s->back_size = buffer_size / 2;
s->buffer = buffer;
s->bm = bm;
s->idle = false;
s->eof = false;
//make sure that we won't wait from cache_fill
//more data than it is allowed to fill
if (s->seek_limit > s->buffer_size - FILL_LIMIT)
s->seek_limit = s->buffer_size - FILL_LIMIT;
for (size_t n = 0; n < s->buffer_size / BYTE_META_CHUNK_SIZE + 2; n++)
s->bm[n] = (struct byte_meta){.stream_pts = MP_NOPTS_VALUE};
return STREAM_OK;
}
static void update_cached_controls(struct priv *s)
{
unsigned int ui;
int64_t i64;
double d;
char **m;
char *t;
s->stream_time_length = 0;
if (stream_control(s->stream, STREAM_CTRL_GET_TIME_LENGTH, &d) == STREAM_OK)
s->stream_time_length = d;
s->stream_start_time = MP_NOPTS_VALUE;
if (stream_control(s->stream, STREAM_CTRL_GET_START_TIME, &d) == STREAM_OK)
s->stream_start_time = d;
s->stream_manages_timeline = false;
if (stream_control(s->stream, STREAM_CTRL_MANAGES_TIMELINE, NULL) == STREAM_OK)
s->stream_manages_timeline = true;
s->stream_num_chapters = 0;
if (stream_control(s->stream, STREAM_CTRL_GET_NUM_CHAPTERS, &ui) == STREAM_OK)
s->stream_num_chapters = ui;
if (stream_control(s->stream, STREAM_CTRL_GET_METADATA, &m) == STREAM_OK) {
talloc_free(s->stream_metadata);
s->stream_metadata = talloc_steal(s, m);
}
if (stream_control(s->stream, STREAM_CTRL_GET_DISC_NAME, &t) == STREAM_OK)
{
talloc_free(s->disc_name);
s->disc_name = talloc_steal(s, t);
}
s->stream_size = -1;
if (stream_control(s->stream, STREAM_CTRL_GET_SIZE, &i64) == STREAM_OK)
s->stream_size = i64;
}
// the core might call these every frame, so cache them...
static int cache_get_cached_control(stream_t *cache, int cmd, void *arg)
{
struct priv *s = cache->priv;
switch (cmd) {
case STREAM_CTRL_GET_CACHE_SIZE:
*(int64_t *)arg = s->buffer_size;
return STREAM_OK;
case STREAM_CTRL_GET_CACHE_FILL:
*(int64_t *)arg = s->max_filepos - s->read_filepos;
return STREAM_OK;
case STREAM_CTRL_GET_CACHE_IDLE:
*(int *)arg = s->idle;
return STREAM_OK;
case STREAM_CTRL_GET_TIME_LENGTH:
*(double *)arg = s->stream_time_length;
return s->stream_time_length ? STREAM_OK : STREAM_UNSUPPORTED;
case STREAM_CTRL_GET_START_TIME:
if (s->stream_start_time == MP_NOPTS_VALUE)
return STREAM_UNSUPPORTED;
*(double *)arg = s->stream_start_time;
return STREAM_OK;
case STREAM_CTRL_GET_SIZE:
if (s->stream_size < 0)
return STREAM_UNSUPPORTED;
*(int64_t *)arg = s->stream_size;
return STREAM_OK;
case STREAM_CTRL_MANAGES_TIMELINE:
return s->stream_manages_timeline ? STREAM_OK : STREAM_UNSUPPORTED;
case STREAM_CTRL_GET_NUM_CHAPTERS:
*(unsigned int *)arg = s->stream_num_chapters;
return STREAM_OK;
case STREAM_CTRL_GET_CURRENT_TIME: {
if (s->read_filepos >= s->min_filepos &&
s->read_filepos <= s->max_filepos &&
s->min_filepos < s->max_filepos)
{
int64_t fpos = FFMIN(s->read_filepos, s->max_filepos - 1);
int64_t pos = fpos - s->offset;
if (pos < 0)
pos += s->buffer_size;
else if (pos >= s->buffer_size)
pos -= s->buffer_size;
double pts = s->bm[pos / BYTE_META_CHUNK_SIZE].stream_pts;
*(double *)arg = pts;
return pts == MP_NOPTS_VALUE ? STREAM_UNSUPPORTED : STREAM_OK;
}
return STREAM_UNSUPPORTED;
}
case STREAM_CTRL_GET_METADATA: {
if (s->stream_metadata && s->stream_metadata[0]) {
char **m = talloc_new(NULL);
int num_m = 0;
for (int n = 0; s->stream_metadata[n]; n++) {
char *t = talloc_strdup(m, s->stream_metadata[n]);
MP_TARRAY_APPEND(NULL, m, num_m, t);
}
MP_TARRAY_APPEND(NULL, m, num_m, NULL);
MP_TARRAY_APPEND(NULL, m, num_m, NULL);
*(char ***)arg = m;
return STREAM_OK;
}
return STREAM_UNSUPPORTED;
}
case STREAM_CTRL_GET_DISC_NAME: {
if (!s->disc_name)
return STREAM_UNSUPPORTED;
*(char **)arg = talloc_strdup(NULL, s->disc_name);
return STREAM_OK;
}
case STREAM_CTRL_RESUME_CACHE:
s->idle = s->eof = false;
pthread_cond_signal(&s->wakeup);
return STREAM_OK;
}
return STREAM_ERROR;
}
static bool control_needs_flush(int stream_ctrl)
{
switch (stream_ctrl) {
case STREAM_CTRL_SEEK_TO_TIME:
case STREAM_CTRL_SET_ANGLE:
case STREAM_CTRL_SET_CURRENT_TITLE:
return true;
}
return false;
}
// Runs in the cache thread
static void cache_execute_control(struct priv *s)
{
uint64_t old_pos = stream_tell(s->stream);
s->control_flush = false;
switch (s->control) {
case STREAM_CTRL_SET_CACHE_SIZE:
s->control_res = resize_cache(s, *(int64_t *)s->control_arg);
break;
default:
s->control_res = stream_control(s->stream, s->control, s->control_arg);
}
bool pos_changed = old_pos != stream_tell(s->stream);
bool ok = s->control_res == STREAM_OK;
if (pos_changed && !ok) {
MP_ERR(s, "STREAM_CTRL changed stream pos but "
"returned error, this is not allowed!\n");
} else if (pos_changed || (ok && control_needs_flush(s->control))) {
MP_VERBOSE(s, "Dropping cache due to control()\n");
s->read_filepos = stream_tell(s->stream);
s->control_flush = true;
cache_drop_contents(s);
}
update_cached_controls(s);
s->control = CACHE_CTRL_NONE;
pthread_cond_signal(&s->wakeup);
}
static void *cache_thread(void *arg)
{
struct priv *s = arg;
pthread_mutex_lock(&s->mutex);
update_cached_controls(s);
double last = mp_time_sec();
while (s->control != CACHE_CTRL_QUIT) {
if (mp_time_sec() - last > CACHE_UPDATE_CONTROLS_TIME) {
update_cached_controls(s);
last = mp_time_sec();
}
if (s->control > 0) {
cache_execute_control(s);
} else {
cache_fill(s);
}
if (s->control == CACHE_CTRL_PING) {
pthread_cond_signal(&s->wakeup);
s->control = CACHE_CTRL_NONE;
}
if (s->idle && s->control == CACHE_CTRL_NONE)
mpthread_cond_timedwait_rel(&s->wakeup, &s->mutex, CACHE_IDLE_SLEEP_TIME);
}
pthread_cond_signal(&s->wakeup);
pthread_mutex_unlock(&s->mutex);
MP_VERBOSE(s, "Cache exiting...\n");
return NULL;
}
static int cache_fill_buffer(struct stream *cache, char *buffer, int max_len)
{
struct priv *s = cache->priv;
assert(s->cache_thread_running);
pthread_mutex_lock(&s->mutex);
if (cache->pos != s->read_filepos)
MP_ERR(s, "!!! read_filepos differs !!! report this bug...\n");
int readb = 0;
if (max_len > 0) {
double retry_time = 0;
int64_t retry = s->reads - 1; // try at least 1 read on EOF
while (1) {
readb = read_buffer(s, buffer, max_len, s->read_filepos);
s->read_filepos += readb;
if (readb > 0)
break;
if (s->eof && s->read_filepos >= s->max_filepos && s->reads >= retry)
break;
s->idle = false;
if (cache_wakeup_and_wait(s, &retry_time) == CACHE_INTERRUPTED)
break;
}
}
// wakeup the cache thread, possibly make it read more data ahead
pthread_cond_signal(&s->wakeup);
pthread_mutex_unlock(&s->mutex);
return readb;
}
static int cache_seek(stream_t *cache, int64_t pos)
{
struct priv *s = cache->priv;
assert(s->cache_thread_running);
int r = 1;
pthread_mutex_lock(&s->mutex);
MP_DBG(s, "request seek: %" PRId64 " <= to=%" PRId64
" (cur=%" PRId64 ") <= %" PRId64 " \n",
s->min_filepos, pos, s->read_filepos, s->max_filepos);
if (!s->seekable && pos > s->max_filepos) {
MP_ERR(s, "Attempting to seek past cached data in unseekable stream.\n");
r = 0;
} else if (!s->seekable && pos < s->min_filepos) {
MP_ERR(s, "Attempting to seek before cached data in unseekable stream.\n");
r = 0;
} else {
cache->pos = s->read_filepos = pos;
s->eof = false; // so that cache_read() will actually wait for new data
pthread_cond_signal(&s->wakeup);
}
pthread_mutex_unlock(&s->mutex);
return r;
}
static int cache_control(stream_t *cache, int cmd, void *arg)
{
struct priv *s = cache->priv;
int r = STREAM_ERROR;
assert(cmd > 0);
pthread_mutex_lock(&s->mutex);
r = cache_get_cached_control(cache, cmd, arg);
if (r != STREAM_ERROR)
goto done;
MP_VERBOSE(s, "blocking for STREAM_CTRL %d\n", cmd);
s->control = cmd;
s->control_arg = arg;
double retry = 0;
while (s->control != CACHE_CTRL_NONE) {
if (cache_wakeup_and_wait(s, &retry) == CACHE_INTERRUPTED) {
s->eof = 1;
r = STREAM_UNSUPPORTED;
goto done;
}
}
r = s->control_res;
if (s->control_flush) {
cache->pos = s->read_filepos;
cache->eof = 0;
cache->buf_pos = cache->buf_len = 0;
}
done:
pthread_mutex_unlock(&s->mutex);
return r;
}
static void cache_uninit(stream_t *cache)
{
struct priv *s = cache->priv;
if (s->cache_thread_running) {
MP_VERBOSE(s, "Terminating cache...\n");
pthread_mutex_lock(&s->mutex);
s->control = CACHE_CTRL_QUIT;
pthread_cond_signal(&s->wakeup);
pthread_mutex_unlock(&s->mutex);
pthread_join(s->cache_thread, NULL);
}
pthread_mutex_destroy(&s->mutex);
pthread_cond_destroy(&s->wakeup);
free(s->buffer);
free(s->bm);
talloc_free(s);
}
// return 1 on success, 0 if the function was interrupted and -1 on error, or
// if the cache is disabled
int stream_cache_init(stream_t *cache, stream_t *stream,
struct mp_cache_opts *opts)
{
if (opts->size < 1)
return -1;
struct priv *s = talloc_zero(NULL, struct priv);
s->log = cache->log;
s->seek_limit = opts->seek_min * 1024ULL;
if (resize_cache(s, opts->size * 1024ULL) != STREAM_OK) {
MP_ERR(s, "Failed to allocate cache buffer.\n");
talloc_free(s);
return -1;
}
MP_VERBOSE(cache, "Cache size set to %" PRId64 " KiB\n",
s->buffer_size / 1024);
pthread_mutex_init(&s->mutex, NULL);
pthread_cond_init(&s->wakeup, NULL);
cache->priv = s;
s->cache = cache;
s->stream = stream;
cache->seek = cache_seek;
cache->fill_buffer = cache_fill_buffer;
cache->control = cache_control;
cache->close = cache_uninit;
int64_t min = opts->initial * 1024ULL;
if (min > s->buffer_size - FILL_LIMIT)
min = s->buffer_size - FILL_LIMIT;
s->seekable = stream->seekable;
if (pthread_create(&s->cache_thread, NULL, cache_thread, s) != 0) {
MP_ERR(s, "Starting cache process/thread failed: %s.\n",
strerror(errno));
return -1;
}
s->cache_thread_running = true;
// wait until cache is filled with at least min bytes
if (min < 1)
return 1;
for (;;) {
if (stream_check_interrupt(cache))
return 0;
int64_t fill;
int idle;
if (stream_control(s->cache, STREAM_CTRL_GET_CACHE_FILL, &fill) < 0)
break;
if (stream_control(s->cache, STREAM_CTRL_GET_CACHE_IDLE, &idle) < 0)
break;
MP_INFO(s, "\rCache fill: %5.2f%% "
"(%" PRId64 " bytes) ", 100.0 * fill / s->buffer_size, fill);
if (fill >= min)
break;
if (idle)
break; // file is smaller than prefill size
// Wake up if the cache is done reading some data (or on timeout/abort)
pthread_mutex_lock(&s->mutex);
s->control = CACHE_CTRL_PING;
pthread_cond_signal(&s->wakeup);
cache_wakeup_and_wait(s, &(double){0});
pthread_mutex_unlock(&s->mutex);
}
MP_INFO(s, "\n");
return 1;
}