static void
base_unmap(tsdn_t *tsdn, extent_hooks_t *extent_hooks, unsigned ind, void *addr,
size_t size) {
/*
* Cascade through dalloc, decommit, purge_forced, and purge_lazy,
* stopping at first success. This cascade is performed for consistency
* with the cascade in extent_dalloc_wrapper() because an application's
* custom hooks may not support e.g. dalloc. This function is only ever
* called as a side effect of arena destruction, so although it might
* seem pointless to do anything besides dalloc here, the application
* may in fact want the end state of all associated virtual memory to be
* in some consistent-but-allocated state.
*/
if (extent_hooks == &extent_hooks_default) {
if (!extent_dalloc_mmap(addr, size)) {
goto label_done;
}
if (!pages_decommit(addr, size)) {
goto label_done;
}
if (!pages_purge_forced(addr, size)) {
goto label_done;
}
if (!pages_purge_lazy(addr, size)) {
goto label_done;
}
/* Nothing worked. This should never happen. */
not_reached();
} else {
tsd_t *tsd = tsdn_null(tsdn) ? tsd_fetch() : tsdn_tsd(tsdn);
pre_reentrancy(tsd, NULL);
if (extent_hooks->dalloc != NULL &&
!extent_hooks->dalloc(extent_hooks, addr, size, true,
ind)) {
goto label_post_reentrancy;
}
if (extent_hooks->decommit != NULL &&
!extent_hooks->decommit(extent_hooks, addr, size, 0, size,
ind)) {
goto label_post_reentrancy;
}
if (extent_hooks->purge_forced != NULL &&
!extent_hooks->purge_forced(extent_hooks, addr, size, 0,
size, ind)) {
goto label_post_reentrancy;
}
if (extent_hooks->purge_lazy != NULL &&
!extent_hooks->purge_lazy(extent_hooks, addr, size, 0, size,
ind)) {
goto label_post_reentrancy;
}
/* Nothing worked. That's the application's problem. */
label_post_reentrancy:
post_reentrancy(tsd);
}
label_done:
if (metadata_thp_madvise()) {
/* Set NOHUGEPAGE after unmap to avoid kernel defrag. */
assert(__builtin_is_aligned(addr, HUGEPAGE) &&
(size & HUGEPAGE_MASK) == 0);
pages_nohuge(addr, size);
}
}
void *
chunk_alloc_dss(arena_t *arena, void *new_addr, size_t size, size_t alignment,
bool *zero, bool *commit)
{
cassert(have_dss);
assert(size > 0 && (size & chunksize_mask) == 0);
assert(alignment > 0 && (alignment & chunksize_mask) == 0);
/*
* sbrk() uses a signed increment argument, so take care not to
* interpret a huge allocation request as a negative increment.
*/
if ((intptr_t)size < 0)
return (NULL);
malloc_mutex_lock(&dss_mtx);
if (dss_prev != (void *)-1) {
/*
* The loop is necessary to recover from races with other
* threads that are using the DSS for something other than
* malloc.
*/
do {
void *ret, *cpad, *dss_next;
size_t gap_size, cpad_size;
intptr_t incr;
/* Avoid an unnecessary system call. */
if (new_addr != NULL && dss_max != new_addr)
break;
/* Get the current end of the DSS. */
dss_max = chunk_dss_sbrk(0);
/* Make sure the earlier condition still holds. */
if (new_addr != NULL && dss_max != new_addr)
break;
/*
* Calculate how much padding is necessary to
* chunk-align the end of the DSS.
*/
gap_size = (chunksize - CHUNK_ADDR2OFFSET(dss_max)) &
chunksize_mask;
/*
* Compute how much chunk-aligned pad space (if any) is
* necessary to satisfy alignment. This space can be
* recycled for later use.
*/
cpad = (void *)((uintptr_t)dss_max + gap_size);
ret = (void *)ALIGNMENT_CEILING((uintptr_t)dss_max,
alignment);
cpad_size = (uintptr_t)ret - (uintptr_t)cpad;
dss_next = (void *)((uintptr_t)ret + size);
if ((uintptr_t)ret < (uintptr_t)dss_max ||
(uintptr_t)dss_next < (uintptr_t)dss_max) {
/* Wrap-around. */
malloc_mutex_unlock(&dss_mtx);
return (NULL);
}
incr = gap_size + cpad_size + size;
dss_prev = chunk_dss_sbrk(incr);
if (dss_prev == dss_max) {
/* Success. */
dss_max = dss_next;
malloc_mutex_unlock(&dss_mtx);
if (cpad_size != 0) {
chunk_hooks_t chunk_hooks =
CHUNK_HOOKS_INITIALIZER;
chunk_dalloc_wrapper(arena,
&chunk_hooks, cpad, cpad_size,
true);
}
if (*zero) {
JEMALLOC_VALGRIND_MAKE_MEM_UNDEFINED(
ret, size);
memset(ret, 0, size);
}
if (!*commit)
*commit = pages_decommit(ret, size);
return (ret);
}
} while (dss_prev != (void *)-1);
}
malloc_mutex_unlock(&dss_mtx);
return (NULL);
}