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FFmpeg/libavcodec/fft_table.h
Andreas Rheinhardt b9c1ab8907 avcodec/fft_template, fft_init_table: Make ff_fft_init() thread-safe
Commit 1af615683e put initializing
the ff_fft_offsets_lut (which is typically used if FFT_FIXED_32)
behind an ff_thread_once() to make ff_fft_init() thread-safe; yet
there is a second place where said table may be initialized which
is not guarded by this AVOnce: ff_fft_init_mips(). MIPS uses this LUT
even for ordinary floating point FFTs, so that ff_fft_init() is not
thread-safe (on MIPS) for both 32bit fixed-point as well as
floating-point FFTs; e.g. ff_mdct_init() inherits this flaw and
therefore initializing e.g. the AAC decoders is not thread-safe (on
MIPS) despite them having FF_CODEC_CAP_INIT_CLEANUP set.

This commit fixes this by moving the AVOnce to fft_init_table.c and
using it to guard all initializations of ff_fft_offsets_lut.

(It is not that bad in practice, because every entry of
ff_fft_offsets_lut is never read during initialization and is only once
ever written to (namely to its final value); but even these are
conflicting actions which are (by definition) data races and lead to
undefined behaviour.)

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
2020-11-24 11:35:03 +01:00

67 lines
2.8 KiB
C

/*
* Copyright (c) 2012
* MIPS Technologies, Inc., California.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the MIPS Technologies, Inc., nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE MIPS TECHNOLOGIES, INC. ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE MIPS TECHNOLOGIES, INC. BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* Authors: Stanislav Ocovaj (socovaj@mips.com)
* Goran Cordasic (goran@mips.com)
* Djordje Pesut (djordje@mips.com)
*
* 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
* definitions and tables for FFT
*/
#ifndef AVCODEC_FFT_TABLE_H
#define AVCODEC_FFT_TABLE_H
#include "libavcodec/fft.h"
#define MAX_LOG2_NFFT 17 //!< Specifies maximum allowed fft size
#define MAX_FFT_SIZE (1 << MAX_LOG2_NFFT)
extern const int32_t ff_w_tab_sr[];
extern uint16_t ff_fft_offsets_lut[];
void ff_fft_lut_init(void);
#endif /* AVCODEC_FFT_TABLE_H */