153 lines
5.0 KiB
Diff
153 lines
5.0 KiB
Diff
From b336944f3a6af4cbd5cf57aa00ef16d30c4ff773 Mon Sep 17 00:00:00 2001
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From: Lasse Collin <lasse.collin@tukaani.org>
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Date: Thu, 3 Apr 2025 14:34:42 +0300
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Subject: [PATCH] liblzma: mt dec: Simplify by removing the THR_STOP state
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The main thread can directly set THR_IDLE in threads_stop() which is
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called when errors are detected. threads_stop() won't return the stopped
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threads to the pool or free the memory pointed by thr->in anymore, but
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it doesn't matter because the existing workers won't be reused after
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an error. The resources will be cleaned up when threads_end() is
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called (reinitializing the decoder always calls threads_end()).
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Reviewed-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
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Thanks-to: Sam James <sam@gentoo.org>
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Upstream: https://github.com/tukaani-project/xz/commit/c0c835964dfaeb2513a3c0bdb642105152fe9f34
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Signed-off-by: Julien Olivain <ju.o@free.fr>
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---
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src/liblzma/common/stream_decoder_mt.c | 75 ++++++++++----------------
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1 file changed, 29 insertions(+), 46 deletions(-)
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diff --git a/src/liblzma/common/stream_decoder_mt.c b/src/liblzma/common/stream_decoder_mt.c
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index 6f06f1d1..e1d07007 100644
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--- a/src/liblzma/common/stream_decoder_mt.c
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+++ b/src/liblzma/common/stream_decoder_mt.c
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@@ -23,15 +23,10 @@ typedef enum {
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THR_IDLE,
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/// Decoding is in progress.
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- /// Main thread may change this to THR_STOP or THR_EXIT.
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+ /// Main thread may change this to THR_IDLE or THR_EXIT.
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/// The worker thread may change this to THR_IDLE.
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THR_RUN,
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- /// The main thread wants the thread to stop whatever it was doing
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- /// but not exit. Main thread may change this to THR_EXIT.
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- /// The worker thread may change this to THR_IDLE.
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- THR_STOP,
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-
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/// The main thread wants the thread to exit.
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THR_EXIT,
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@@ -346,27 +341,6 @@ worker_enable_partial_update(void *thr_ptr)
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}
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-/// Things do to at THR_STOP or when finishing a Block.
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-/// This is called with thr->coder->mutex locked.
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-static void
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-worker_stop(struct worker_thread *thr)
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-{
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- // Update memory usage counters.
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- thr->coder->mem_in_use -= thr->in_size;
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- thr->in_size = 0; // thr->in was freed above.
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-
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- thr->coder->mem_in_use -= thr->mem_filters;
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- thr->coder->mem_cached += thr->mem_filters;
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-
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- // Put this thread to the stack of free threads.
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- thr->next = thr->coder->threads_free;
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- thr->coder->threads_free = thr;
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-
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- mythread_cond_signal(&thr->coder->cond);
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- return;
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-}
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-
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-
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static MYTHREAD_RET_TYPE
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worker_decoder(void *thr_ptr)
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{
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@@ -397,17 +371,6 @@ next_loop_unlocked:
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return MYTHREAD_RET_VALUE;
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}
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- if (thr->state == THR_STOP) {
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- thr->state = THR_IDLE;
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- mythread_mutex_unlock(&thr->mutex);
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-
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- mythread_sync(thr->coder->mutex) {
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- worker_stop(thr);
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- }
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-
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- goto next_loop_lock;
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- }
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-
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assert(thr->state == THR_RUN);
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// Update progress info for get_progress().
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@@ -510,7 +473,22 @@ next_loop_unlocked:
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&& thr->coder->thread_error == LZMA_OK)
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thr->coder->thread_error = ret;
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- worker_stop(thr);
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+ // Return the worker thread to the stack of available
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+ // threads.
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+ {
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+ // Update memory usage counters.
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+ thr->coder->mem_in_use -= thr->in_size;
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+ thr->in_size = 0; // thr->in was freed above.
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+
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+ thr->coder->mem_in_use -= thr->mem_filters;
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+ thr->coder->mem_cached += thr->mem_filters;
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+
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+ // Put this thread to the stack of free threads.
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+ thr->next = thr->coder->threads_free;
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+ thr->coder->threads_free = thr;
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+ }
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+
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+ mythread_cond_signal(&thr->coder->cond);
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}
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goto next_loop_lock;
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@@ -544,17 +522,22 @@ threads_end(struct lzma_stream_coder *coder, const lzma_allocator *allocator)
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}
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+/// Tell worker threads to stop without doing any cleaning up.
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+/// The clean up will be done when threads_exit() is called;
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+/// it's not possible to reuse the threads after threads_stop().
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+///
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+/// This is called before returning an unrecoverable error code
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+/// to the application. It would be waste of processor time
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+/// to keep the threads running in such a situation.
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static void
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threads_stop(struct lzma_stream_coder *coder)
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{
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for (uint32_t i = 0; i < coder->threads_initialized; ++i) {
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+ // The threads that are in the THR_RUN state will stop
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+ // when they check the state the next time. There's no
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+ // need to signal coder->threads[i].cond.
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mythread_sync(coder->threads[i].mutex) {
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- // The state must be changed conditionally because
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- // THR_IDLE -> THR_STOP is not a valid state change.
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- if (coder->threads[i].state != THR_IDLE) {
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- coder->threads[i].state = THR_STOP;
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- mythread_cond_signal(&coder->threads[i].cond);
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- }
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+ coder->threads[i].state = THR_IDLE;
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}
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}
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@@ -1948,7 +1931,7 @@ stream_decoder_mt_init(lzma_next_coder *next, const lzma_allocator *allocator,
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// accounting from scratch, too. Changes in filter and block sizes may
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// affect number of threads.
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//
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- // FIXME? Reusing should be easy but unlike the single-threaded
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+ // Reusing threads doesn't seem worth it. Unlike the single-threaded
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// decoder, with some types of input file combinations reusing
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// could leave quite a lot of memory allocated but unused (first
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// file could allocate a lot, the next files could use fewer
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--
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2.49.0
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