a011c4c22d
This fixes an incorrect debug-mode assert: - T1 starts an arena stats update and reads stack_head from another thread's cache bin, when that cache bin has 1 item in it. - T2 allocates from that cache bin. The cache_bin's stack_head now points to a NULL pointer, since the cache bin is empty. - T1 Re-reads the cache_bin's stack_head to perform an assertion check (since it previously saw that the bin was empty, whatever stack_head points to should be non-NULL).
96 lines
3.0 KiB
C
96 lines
3.0 KiB
C
#include "jemalloc/internal/jemalloc_preamble.h"
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#include "jemalloc/internal/jemalloc_internal_includes.h"
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#include "jemalloc/internal/bit_util.h"
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void
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cache_bin_info_init(cache_bin_info_t *info,
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cache_bin_sz_t ncached_max) {
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assert(ncached_max <= CACHE_BIN_NCACHED_MAX);
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size_t stack_size = (size_t)ncached_max * sizeof(void *);
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assert(stack_size < ((size_t)1 << (sizeof(cache_bin_sz_t) * 8)));
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info->ncached_max = (cache_bin_sz_t)ncached_max;
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}
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void
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cache_bin_info_compute_alloc(cache_bin_info_t *infos, szind_t ninfos,
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size_t *size, size_t *alignment) {
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/* For the total bin stack region (per tcache), reserve 2 more slots so
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* that
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* 1) the empty position can be safely read on the fast path before
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* checking "is_empty"; and
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* 2) the cur_ptr can go beyond the empty position by 1 step safely on
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* the fast path (i.e. no overflow).
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*/
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*size = sizeof(void *) * 2;
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for (szind_t i = 0; i < ninfos; i++) {
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assert(infos[i].ncached_max > 0);
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*size += infos[i].ncached_max * sizeof(void *);
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}
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/*
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* Align to at least PAGE, to minimize the # of TLBs needed by the
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* smaller sizes; also helps if the larger sizes don't get used at all.
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*/
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*alignment = PAGE;
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}
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void
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cache_bin_preincrement(cache_bin_info_t *infos, szind_t ninfos, void *alloc,
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size_t *cur_offset) {
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if (config_debug) {
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size_t computed_size;
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size_t computed_alignment;
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/* Pointer should be as aligned as we asked for. */
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cache_bin_info_compute_alloc(infos, ninfos, &computed_size,
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&computed_alignment);
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assert(((uintptr_t)alloc & (computed_alignment - 1)) == 0);
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}
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*(uintptr_t *)((uintptr_t)alloc + *cur_offset) =
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cache_bin_preceding_junk;
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*cur_offset += sizeof(void *);
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}
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void
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cache_bin_postincrement(cache_bin_info_t *infos, szind_t ninfos, void *alloc,
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size_t *cur_offset) {
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*(uintptr_t *)((uintptr_t)alloc + *cur_offset) =
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cache_bin_trailing_junk;
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*cur_offset += sizeof(void *);
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}
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void
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cache_bin_init(cache_bin_t *bin, cache_bin_info_t *info, void *alloc,
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size_t *cur_offset) {
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/*
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* The full_position points to the lowest available space. Allocations
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* will access the slots toward higher addresses (for the benefit of
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* adjacent prefetch).
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*/
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void *stack_cur = (void *)((uintptr_t)alloc + *cur_offset);
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void *full_position = stack_cur;
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uint16_t bin_stack_size = info->ncached_max * sizeof(void *);
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*cur_offset += bin_stack_size;
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void *empty_position = (void *)((uintptr_t)alloc + *cur_offset);
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/* Init to the empty position. */
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bin->stack_head = (void **)empty_position;
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bin->low_bits_low_water = (uint16_t)(uintptr_t)bin->stack_head;
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bin->low_bits_full = (uint16_t)(uintptr_t)full_position;
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bin->low_bits_empty = (uint16_t)(uintptr_t)empty_position;
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assert(cache_bin_diff(bin, bin->low_bits_full,
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(uint16_t)(uintptr_t) bin->stack_head) == bin_stack_size);
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assert(cache_bin_ncached_get_local(bin, info) == 0);
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assert(cache_bin_empty_position_get(bin) == empty_position);
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assert(bin_stack_size > 0 || empty_position == full_position);
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}
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bool
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cache_bin_still_zero_initialized(cache_bin_t *bin) {
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return bin->stack_head == NULL;
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}
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