jemalloc/src/jemalloc_fork.c

#include "jemalloc/internal/jemalloc_preamble.h"
#include "jemalloc/internal/jemalloc_internal_includes.h"

#include "jemalloc/internal/arenas_management.h"
#include "jemalloc/internal/ctl.h"
#include "jemalloc/internal/jemalloc_fork.h"
#include "jemalloc/internal/jemalloc_init.h"

/******************************************************************************/
/*
 * The following functions are used by threading libraries for protection of
 * malloc during fork().
 */

#ifdef JEMALLOC_MUTEX_INIT_CB
/*
 * When JEMALLOC_MUTEX_INIT_CB is defined, pthread_atfork registration is
 * skipped and the platform calls _malloc_prefork/_malloc_postfork directly.
 * FreeBSD's libthr calls _malloc_postfork in both parent and child.  Detect
 * the child by pid change so we route to jemalloc_postfork_child, which resets
 * per-arena state the parent handler does not touch (nthreads, descriptor
 * queues).  The check is harmless on any platform that only calls
 * _malloc_postfork in the parent.
 */
static pid_t jemalloc_prefork_pid;
#endif

#ifndef JEMALLOC_MUTEX_INIT_CB
void
jemalloc_prefork(void)
#else
JEMALLOC_EXPORT void
_malloc_prefork(void)
#endif
{
	tsd_t   *tsd;
	unsigned i, j, narenas;
	arena_t *arena;

#ifdef JEMALLOC_MUTEX_INIT_CB
	if (!malloc_initialized()) {
		return;
	}
#endif
	assert(malloc_initialized());

#ifdef JEMALLOC_MUTEX_INIT_CB
	jemalloc_prefork_pid = getpid();
#endif

	tsd = tsd_fetch();

	narenas = narenas_total_get();

	witness_prefork(tsd_witness_tsdp_get(tsd));
	/* Acquire all mutexes in a safe order. */
	ctl_prefork(tsd_tsdn(tsd));
	tcache_prefork(tsd_tsdn(tsd));
	arenas_management_prefork(tsd_tsdn(tsd));
	if (have_background_thread) {
		background_thread_prefork0(tsd_tsdn(tsd));
	}
	prof_prefork0(tsd_tsdn(tsd));
	if (have_background_thread) {
		background_thread_prefork1(tsd_tsdn(tsd));
	}
	/* Break arena prefork into stages to preserve lock order. */
	for (i = 0; i < 9; i++) {
		for (j = 0; j < narenas; j++) {
			if ((arena = arena_get(tsd_tsdn(tsd), j, false))
			    != NULL) {
				switch (i) {
				case 0:
					arena_prefork0(tsd_tsdn(tsd), arena);
					break;
				case 1:
					arena_prefork1(tsd_tsdn(tsd), arena);
					break;
				case 2:
					arena_prefork2(tsd_tsdn(tsd), arena);
					break;
				case 3:
					arena_prefork3(tsd_tsdn(tsd), arena);
					break;
				case 4:
					arena_prefork4(tsd_tsdn(tsd), arena);
					break;
				case 5:
					arena_prefork5(tsd_tsdn(tsd), arena);
					break;
				case 6:
					arena_prefork6(tsd_tsdn(tsd), arena);
					break;
				case 7:
					arena_prefork7(tsd_tsdn(tsd), arena);
					break;
				case 8:
					arena_prefork8(tsd_tsdn(tsd), arena);
					break;
				default:
					not_reached();
				}
			}
		}
	}
	prof_prefork1(tsd_tsdn(tsd));
	stats_prefork(tsd_tsdn(tsd));
}

#ifndef JEMALLOC_MUTEX_INIT_CB
void
jemalloc_postfork_parent(void)
#else
JEMALLOC_EXPORT void
_malloc_postfork(void)
#endif
{
	tsd_t   *tsd;
	unsigned i, narenas;

#ifdef JEMALLOC_MUTEX_INIT_CB
	if (!malloc_initialized()) {
		return;
	}
	if (getpid() != jemalloc_prefork_pid) {
		jemalloc_postfork_child();
		return;
	}
#endif
	assert(malloc_initialized());

	tsd = tsd_fetch();

	witness_postfork_parent(tsd_witness_tsdp_get(tsd));
	/* Release all mutexes, now that fork() has completed. */
	stats_postfork_parent(tsd_tsdn(tsd));
	for (i = 0, narenas = narenas_total_get(); i < narenas; i++) {
		arena_t *arena;

		if ((arena = arena_get(tsd_tsdn(tsd), i, false)) != NULL) {
			arena_postfork_parent(tsd_tsdn(tsd), arena);
		}
	}
	prof_postfork_parent(tsd_tsdn(tsd));
	if (have_background_thread) {
		background_thread_postfork_parent(tsd_tsdn(tsd));
	}
	arenas_management_postfork_parent(tsd_tsdn(tsd));
	tcache_postfork_parent(tsd_tsdn(tsd));
	ctl_postfork_parent(tsd_tsdn(tsd));
}

void
jemalloc_postfork_child(void) {
	tsd_t   *tsd;
	unsigned i, narenas;

	assert(malloc_initialized());

	tsd = tsd_fetch();

	witness_postfork_child(tsd_witness_tsdp_get(tsd));
	/* Release all mutexes, now that fork() has completed. */
	stats_postfork_child(tsd_tsdn(tsd));
	for (i = 0, narenas = narenas_total_get(); i < narenas; i++) {
		arena_t *arena;

		if ((arena = arena_get(tsd_tsdn(tsd), i, false)) != NULL) {
			cache_bin_array_descriptor_t *desc =
			    tcache_postfork_arena_descriptor(
			        tsd_tsdn(tsd), arena);
			arena_postfork_child(tsd_tsdn(tsd), arena, desc);
		}
	}
	prof_postfork_child(tsd_tsdn(tsd));
	if (have_background_thread) {
		background_thread_postfork_child(tsd_tsdn(tsd));
	}
	arenas_management_postfork_child(tsd_tsdn(tsd));
	tcache_postfork_child(tsd_tsdn(tsd));
	ctl_postfork_child(tsd_tsdn(tsd));
}