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liblzma: mt dec: Fix lack of parallelization in single-shot decoding

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Single-shot decoding means calling lzma_code() by giving it the whole
input at once and enough output buffer space to store the uncompressed
data, and combining this with LZMA_FINISH and no timeout
(lzma_mt.timeout = 0). This way the file is decoded with a single
lzma_code() call if possible.

The bug prevented the decoder from starting more than one worker thread
in single-shot mode. The issue was noticed when reviewing the code;
there are no bug reports. Thus maybe few have tried this mode.

Fixes: 64b6d496dc81 ("liblzma: Threaded decoder: Always wait for output if LZMA_FINISH is used.")
(cherry picked from commit 0c80045ab82c406858d9d5bcea9f48ebc3d0a81d)
This commit is contained in:
Lasse Collin 2025-04-03 14:34:42 +03:00
parent c8bb46c5a1
commit 20ec36eafd
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GPG Key ID: 38EE757D69184620
1 changed files with 9 additions and 2 deletions
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11
src/liblzma/common/stream_decoder_mt.c
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@ -1544,10 +1544,17 @@ stream_decode_mt(void *coder_ptr, const lzma_allocator *allocator,
// Read output from the output queue. Just like in
// SEQ_BLOCK_HEADER, we wait to fill the output buffer
// only if waiting_allowed was set to true in the beginning
// of this function (see the comment there).
// of this function (see the comment there) and there is
// no input available. In SEQ_BLOCK_HEADER, there is never
// input available when read_output_and_wait() is called,
// but here there can be when LZMA_FINISH is used, thus we
// need to check if *in_pos == in_size. Otherwise we would
// wait here instead of using the available input to start
// a new thread.
return_if_error(read_output_and_wait(coder, allocator,
out, out_pos, out_size,
NULL, waiting_allowed,
NULL,
waiting_allowed && *in_pos == in_size,
&wait_abs, &has_blocked));
if (coder->pending_error != LZMA_OK) {