project-base/server-skynet-source-3rd-jemalloc
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Fix a race in extent_grow_retained().

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Set extent as active prior to registration so that other threads can't
modify it in the absence of locking.

This regression was introduced by
d27f29b468 (Disentangle arena and extent
locking.), via non-obvious means.  Removal of extents_mtx protection
during extent_grow_retained() execution opened up the race, but in the
presence of that locking, the code was safe.

This resolves #599.
This commit is contained in:
Jason Evans 2017-02-04 00:43:32 -08:00
parent 1bac516aaa
commit 6737d5f61e
1 changed files with 14 additions and 9 deletions
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23
src/extent.c
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@ -453,7 +453,7 @@ extent_gdump_sub(tsdn_t *tsdn, const extent_t *extent) {
}
static bool
extent_register(tsdn_t *tsdn, const extent_t *extent) {
extent_register_impl(tsdn_t *tsdn, const extent_t *extent, bool gdump_add) {
rtree_ctx_t rtree_ctx_fallback;
rtree_ctx_t *rtree_ctx = tsdn_rtree_ctx(tsdn, &rtree_ctx_fallback);
rtree_elm_t *elm_a, *elm_b;
@ -468,13 +468,23 @@ extent_register(tsdn_t *tsdn, const extent_t *extent) {
}
extent_rtree_release(tsdn, elm_a, elm_b);
if (config_prof) {
if (config_prof && gdump_add) {
extent_gdump_add(tsdn, extent);
}
return false;
}
static bool
extent_register(tsdn_t *tsdn, const extent_t *extent) {
return extent_register_impl(tsdn, extent, true);
}
static bool
extent_register_no_gdump_add(tsdn_t *tsdn, const extent_t *extent) {
return extent_register_impl(tsdn, extent, false);
}
static void
extent_reregister(tsdn_t *tsdn, const extent_t *extent) {
bool err = extent_register(tsdn, extent);
@ -827,17 +837,12 @@ extent_grow_retained(tsdn_t *tsdn, arena_t *arena,
ptr = extent_alloc_core(tsdn, arena, new_addr, alloc_size, PAGE,
&zeroed, &committed, arena->dss_prec);
extent_init(extent, arena, ptr, alloc_size, alloc_size,
arena_extent_sn_next(arena), extent_state_retained, zeroed,
arena_extent_sn_next(arena), extent_state_active, zeroed,
committed, false);
if (ptr == NULL || extent_register(tsdn, extent)) {
if (ptr == NULL || extent_register_no_gdump_add(tsdn, extent)) {
extent_dalloc(tsdn, arena, extent);
return NULL;
}
/*
* Set the extent as active *after registration so that no gdump-related
* accounting occurs during registration.
*/
extent_state_set(extent, extent_state_active);
leadsize = ALIGNMENT_CEILING((uintptr_t)ptr, PAGE_CEILING(alignment)) -
(uintptr_t)ptr;