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San: Unguard guarded slabs during arena destruction

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When opt_retain is on, slab extents remain guarded in all states, even
retained. This works well if arena is never destroyed, because we
anticipate those slabs will be eventually reused. But if the arena is
destroyed, the slabs must be unguarded to prevent leaking guard pages.
This commit is contained in:
Alex Lapenkou 2021-11-02 15:56:36 -07:00 • committed by Alexander Lapenkov
parent b6a7a535b3
commit 6cb585b13a
3 changed files with 42 additions and 10 deletions
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8
src/extent.c
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@ -1057,12 +1057,14 @@ extent_destroy_wrapper(tsdn_t *tsdn, pac_t *pac, ehooks_t *ehooks,
edata_t *edata) {
assert(edata_base_get(edata) != NULL);
assert(edata_size_get(edata) != 0);
assert(edata_state_get(edata) == extent_state_retained);
assert(emap_edata_is_acquired(tsdn, pac->emap, edata));
witness_assert_depth_to_rank(tsdn_witness_tsdp_get(tsdn),
WITNESS_RANK_CORE, 0);
/* Deregister first to avoid a race with other allocating threads. */
extent_deregister(tsdn, pac, edata);
if (edata_guarded_get(edata)) {
unguard_pages_pre_destroy(tsdn, ehooks, edata, pac->emap);
}
edata_addr_set(edata, edata_base_get(edata));
/* Try to destroy; silently fail otherwise. */