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#define JEMALLOC_CHUNK_DSS_C_
#include "jemalloc/internal/jemalloc_internal.h"
/******************************************************************************/
/* Data. */
/*
* Protects sbrk() calls. This avoids malloc races among threads, though it
* does not protect against races with threads that call sbrk() directly.
*/
static malloc_mutex_t dss_mtx;
/* Base address of the DSS. */
static void *dss_base;
/* Current end of the DSS, or ((void *)-1) if the DSS is exhausted. */
static void *dss_prev;
/* Current upper limit on DSS addresses. */
static void *dss_max;
/******************************************************************************/
#ifndef JEMALLOC_HAVE_SBRK
static void *
sbrk(intptr_t increment)
{
not_implemented();
return (NULL);
}
#endif
void *
chunk_alloc_dss(size_t size, size_t alignment, bool *zero)
{
void *ret;
cassert(config_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) {
size_t gap_size, cpad_size;
void *cpad, *dss_next;
intptr_t incr;
/*
* The loop is necessary to recover from races with other
* threads that are using the DSS for something other than
* malloc.
*/
do {
/* Get the current end of the DSS. */
dss_max = sbrk(0);
/*
* 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 = sbrk(incr);
if (dss_prev == dss_max) {
/* Success. */
dss_max = dss_next;
malloc_mutex_unlock(&dss_mtx);
if (cpad_size != 0)
chunk_dealloc(cpad, cpad_size, true);
*zero = true;
return (ret);
}
} while (dss_prev != (void *)-1);
}
malloc_mutex_unlock(&dss_mtx);
return (NULL);
}
bool
chunk_in_dss(void *chunk)
{
bool ret;
cassert(config_dss);
malloc_mutex_lock(&dss_mtx);
if ((uintptr_t)chunk >= (uintptr_t)dss_base
&& (uintptr_t)chunk < (uintptr_t)dss_max)
ret = true;
else
ret = false;
malloc_mutex_unlock(&dss_mtx);
return (ret);
}
bool
chunk_dss_boot(void)
{
cassert(config_dss);
if (malloc_mutex_init(&dss_mtx))
return (true);
dss_base = sbrk(0);
dss_prev = dss_base;
dss_max = dss_base;
return (false);
}
void
chunk_dss_prefork(void)
{
if (config_dss)
malloc_mutex_prefork(&dss_mtx);
}
void
chunk_dss_postfork_parent(void)
{
if (config_dss)
malloc_mutex_postfork_parent(&dss_mtx);
}
void
chunk_dss_postfork_child(void)
{
if (config_dss)
malloc_mutex_postfork_child(&dss_mtx);
}
/******************************************************************************/
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