FFmpeg/libavcodec/pthread_slice.c
Andreas Rheinhardt 0639f5c294 avcodec/pthread_slice: Don't use static variable, fix race
ff_slice_thread_init() uses a static variable to hold a function
pointer, although the value of said pointer needn't be saved between
different runs of this function at all.

The reason for this being so is probably that said pointer points to
a static function (if used); but storage class specifiers like "static"
are not part of the type of an object and so including it in the pointer
declaration is wrong (anyway, "static" means different things in both
contexts: for the function declaration it affects linkage, for the
variable storage duration).

Using a static variable here can lead to races, e.g. when initializing
VP9 (for which said function pointer was added) and H.264 with slice
threading. The latter has the FF_CODEC_CAP_INIT_THREADSAFE flag set and
is therefore unaffected by the lock guarding initializations of
decoders.

Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
2020-12-02 16:11:50 +01:00

243 lines
7.4 KiB
C

/*
* This file is part of FFmpeg.
*
* FFmpeg 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.
*
* FFmpeg 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 FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* Slice multithreading support functions
* @see doc/multithreading.txt
*/
#include "config.h"
#include "avcodec.h"
#include "internal.h"
#include "pthread_internal.h"
#include "thread.h"
#include "libavutil/avassert.h"
#include "libavutil/common.h"
#include "libavutil/cpu.h"
#include "libavutil/mem.h"
#include "libavutil/thread.h"
#include "libavutil/slicethread.h"
typedef int (action_func)(AVCodecContext *c, void *arg);
typedef int (action_func2)(AVCodecContext *c, void *arg, int jobnr, int threadnr);
typedef int (main_func)(AVCodecContext *c);
typedef struct SliceThreadContext {
AVSliceThread *thread;
action_func *func;
action_func2 *func2;
main_func *mainfunc;
void *args;
int *rets;
int job_size;
int *entries;
int entries_count;
int thread_count;
pthread_cond_t *progress_cond;
pthread_mutex_t *progress_mutex;
} SliceThreadContext;
static void main_function(void *priv) {
AVCodecContext *avctx = priv;
SliceThreadContext *c = avctx->internal->thread_ctx;
c->mainfunc(avctx);
}
static void worker_func(void *priv, int jobnr, int threadnr, int nb_jobs, int nb_threads)
{
AVCodecContext *avctx = priv;
SliceThreadContext *c = avctx->internal->thread_ctx;
int ret;
ret = c->func ? c->func(avctx, (char *)c->args + c->job_size * jobnr)
: c->func2(avctx, c->args, jobnr, threadnr);
if (c->rets)
c->rets[jobnr] = ret;
}
void ff_slice_thread_free(AVCodecContext *avctx)
{
SliceThreadContext *c = avctx->internal->thread_ctx;
int i;
avpriv_slicethread_free(&c->thread);
for (i = 0; i < c->thread_count; i++) {
pthread_mutex_destroy(&c->progress_mutex[i]);
pthread_cond_destroy(&c->progress_cond[i]);
}
av_freep(&c->entries);
av_freep(&c->progress_mutex);
av_freep(&c->progress_cond);
av_freep(&avctx->internal->thread_ctx);
}
static int thread_execute(AVCodecContext *avctx, action_func* func, void *arg, int *ret, int job_count, int job_size)
{
SliceThreadContext *c = avctx->internal->thread_ctx;
if (!(avctx->active_thread_type&FF_THREAD_SLICE) || avctx->thread_count <= 1)
return avcodec_default_execute(avctx, func, arg, ret, job_count, job_size);
if (job_count <= 0)
return 0;
c->job_size = job_size;
c->args = arg;
c->func = func;
c->rets = ret;
avpriv_slicethread_execute(c->thread, job_count, !!c->mainfunc );
return 0;
}
static int thread_execute2(AVCodecContext *avctx, action_func2* func2, void *arg, int *ret, int job_count)
{
SliceThreadContext *c = avctx->internal->thread_ctx;
c->func2 = func2;
return thread_execute(avctx, NULL, arg, ret, job_count, 0);
}
int ff_slice_thread_execute_with_mainfunc(AVCodecContext *avctx, action_func2* func2, main_func *mainfunc, void *arg, int *ret, int job_count)
{
SliceThreadContext *c = avctx->internal->thread_ctx;
c->func2 = func2;
c->mainfunc = mainfunc;
return thread_execute(avctx, NULL, arg, ret, job_count, 0);
}
int ff_slice_thread_init(AVCodecContext *avctx)
{
SliceThreadContext *c;
int thread_count = avctx->thread_count;
void (*mainfunc)(void *);
// We cannot do this in the encoder init as the threads are created before
if (av_codec_is_encoder(avctx->codec) &&
avctx->codec_id == AV_CODEC_ID_MPEG1VIDEO &&
avctx->height > 2800)
thread_count = avctx->thread_count = 1;
if (!thread_count) {
int nb_cpus = av_cpu_count();
if (avctx->height)
nb_cpus = FFMIN(nb_cpus, (avctx->height+15)/16);
// use number of cores + 1 as thread count if there is more than one
if (nb_cpus > 1)
thread_count = avctx->thread_count = FFMIN(nb_cpus + 1, MAX_AUTO_THREADS);
else
thread_count = avctx->thread_count = 1;
}
if (thread_count <= 1) {
avctx->active_thread_type = 0;
return 0;
}
avctx->internal->thread_ctx = c = av_mallocz(sizeof(*c));
mainfunc = avctx->codec->caps_internal & FF_CODEC_CAP_SLICE_THREAD_HAS_MF ? &main_function : NULL;
if (!c || (thread_count = avpriv_slicethread_create(&c->thread, avctx, worker_func, mainfunc, thread_count)) <= 1) {
if (c)
avpriv_slicethread_free(&c->thread);
av_freep(&avctx->internal->thread_ctx);
avctx->thread_count = 1;
avctx->active_thread_type = 0;
return 0;
}
avctx->thread_count = thread_count;
avctx->execute = thread_execute;
avctx->execute2 = thread_execute2;
return 0;
}
void ff_thread_report_progress2(AVCodecContext *avctx, int field, int thread, int n)
{
SliceThreadContext *p = avctx->internal->thread_ctx;
int *entries = p->entries;
pthread_mutex_lock(&p->progress_mutex[thread]);
entries[field] +=n;
pthread_cond_signal(&p->progress_cond[thread]);
pthread_mutex_unlock(&p->progress_mutex[thread]);
}
void ff_thread_await_progress2(AVCodecContext *avctx, int field, int thread, int shift)
{
SliceThreadContext *p = avctx->internal->thread_ctx;
int *entries = p->entries;
if (!entries || !field) return;
thread = thread ? thread - 1 : p->thread_count - 1;
pthread_mutex_lock(&p->progress_mutex[thread]);
while ((entries[field - 1] - entries[field]) < shift){
pthread_cond_wait(&p->progress_cond[thread], &p->progress_mutex[thread]);
}
pthread_mutex_unlock(&p->progress_mutex[thread]);
}
int ff_alloc_entries(AVCodecContext *avctx, int count)
{
int i;
if (avctx->active_thread_type & FF_THREAD_SLICE) {
SliceThreadContext *p = avctx->internal->thread_ctx;
if (p->entries) {
av_assert0(p->thread_count == avctx->thread_count);
av_freep(&p->entries);
}
p->thread_count = avctx->thread_count;
p->entries = av_mallocz_array(count, sizeof(int));
if (!p->progress_mutex) {
p->progress_mutex = av_malloc_array(p->thread_count, sizeof(pthread_mutex_t));
p->progress_cond = av_malloc_array(p->thread_count, sizeof(pthread_cond_t));
}
if (!p->entries || !p->progress_mutex || !p->progress_cond) {
av_freep(&p->entries);
av_freep(&p->progress_mutex);
av_freep(&p->progress_cond);
return AVERROR(ENOMEM);
}
p->entries_count = count;
for (i = 0; i < p->thread_count; i++) {
pthread_mutex_init(&p->progress_mutex[i], NULL);
pthread_cond_init(&p->progress_cond[i], NULL);
}
}
return 0;
}
void ff_reset_entries(AVCodecContext *avctx)
{
SliceThreadContext *p = avctx->internal->thread_ctx;
memset(p->entries, 0, p->entries_count * sizeof(int));
}