Fix arena chunk purge/dealloc race conditions.
Fix arena_chunk_dealloc() to put the new spare in a consistent state before dropping the arena mutex to deallocate the previous spare. Fix arena_run_dalloc() to insert a newly dirtied chunk into the chunks_dirty list before potentially deallocating the chunk, so that dirty page accounting is self-consistent.
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@ -470,23 +470,6 @@ arena_chunk_dealloc(arena_t *arena, arena_chunk_t *chunk)
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{
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arena_avail_tree_t *runs_avail;
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while (arena->spare != NULL) {
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arena_chunk_t *spare = arena->spare;
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arena->spare = NULL;
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if (spare->dirtied) {
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ql_remove(&chunk->arena->chunks_dirty, spare,
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link_dirty);
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arena->ndirty -= spare->ndirty;
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}
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malloc_mutex_unlock(&arena->lock);
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chunk_dealloc((void *)spare, chunksize);
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malloc_mutex_lock(&arena->lock);
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#ifdef JEMALLOC_STATS
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arena->stats.mapped -= chunksize;
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#endif
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}
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/*
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* Remove run from the appropriate runs_avail_* tree, so that the arena
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* does not use it.
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@ -499,6 +482,22 @@ arena_chunk_dealloc(arena_t *arena, arena_chunk_t *chunk)
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arena_avail_tree_remove(runs_avail,
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&chunk->map[arena_chunk_header_npages]);
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if (arena->spare != NULL) {
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arena_chunk_t *spare = arena->spare;
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arena->spare = chunk;
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if (spare->dirtied) {
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ql_remove(&chunk->arena->chunks_dirty, spare,
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link_dirty);
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arena->ndirty -= spare->ndirty;
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}
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malloc_mutex_unlock(&arena->lock);
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chunk_dealloc((void *)spare, chunksize);
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malloc_mutex_lock(&arena->lock);
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#ifdef JEMALLOC_STATS
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arena->stats.mapped -= chunksize;
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#endif
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} else
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arena->spare = chunk;
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}
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@ -925,6 +924,18 @@ arena_run_dalloc(arena_t *arena, arena_run_t *run, bool dirty)
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/* Insert into runs_avail, now that coalescing is complete. */
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arena_avail_tree_insert(runs_avail, &chunk->map[run_ind]);
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if (dirty) {
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/*
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* Insert into chunks_dirty before potentially calling
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* arena_chunk_dealloc(), so that chunks_dirty and
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* arena->ndirty are consistent.
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*/
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if (chunk->dirtied == false) {
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ql_tail_insert(&arena->chunks_dirty, chunk, link_dirty);
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chunk->dirtied = true;
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}
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}
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/*
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* Deallocate chunk if it is now completely unused. The bit
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* manipulation checks whether the first run is unallocated and extends
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@ -935,19 +946,14 @@ arena_run_dalloc(arena_t *arena, arena_run_t *run, bool dirty)
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arena_chunk_dealloc(arena, chunk);
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/*
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* It is okay to do dirty page processing even if the chunk was
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* It is okay to do dirty page processing here even if the chunk was
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* deallocated above, since in that case it is the spare. Waiting
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* until after possible chunk deallocation to do dirty processing
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* allows for an old spare to be fully deallocated, thus decreasing the
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* chances of spuriously crossing the dirty page purging threshold.
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*/
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if (dirty) {
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if (chunk->dirtied == false) {
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ql_tail_insert(&arena->chunks_dirty, chunk, link_dirty);
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chunk->dirtied = true;
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}
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if (dirty)
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arena_maybe_purge(arena);
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}
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}
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static void
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