mirror of
https://github.com/jemalloc/jemalloc.git
synced 2026-05-30 08:37:29 +03:00
Add follow-up test for postfork multithread
Fix FreeBSD postfork child handler never being called: FreeBSD's libthr calls _malloc_postfork in both parent and child (see freebsd-src lib/libthr/thread/thr_fork.c), but jemalloc mapped it to the parent handler only. Detect the child via getpid() and route to jemalloc_postfork_child, which resets nthreads and rebuilds the descriptor queue. Remove the child_survivor_bytes vs pre_survivor_bytes comparison: on macOS where jemalloc registers as the default zone, internal allocations during the postfork handler (pthread_mutex_init) can inflate the surviving thread's tcache. Add double-fork test to verify prefork pid is refreshed correctly when a child process forks again.
This commit is contained in:
Slobodan Predolac
parent
300b58b49b
commit
00f53eb337
2 changed files with 300 additions and 1 deletions
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@ -12,6 +12,19 @@
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* malloc during fork().
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*/
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#ifdef JEMALLOC_MUTEX_INIT_CB
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/*
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* When JEMALLOC_MUTEX_INIT_CB is defined, pthread_atfork registration is
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* skipped and the platform calls _malloc_prefork/_malloc_postfork directly.
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* FreeBSD's libthr calls _malloc_postfork in both parent and child. Detect
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* the child by pid change so we route to jemalloc_postfork_child, which resets
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* per-arena state the parent handler does not touch (nthreads, descriptor
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* queues). The check is harmless on any platform that only calls
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* _malloc_postfork in the parent.
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*/
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static pid_t jemalloc_prefork_pid;
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#endif
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#ifndef JEMALLOC_MUTEX_INIT_CB
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void
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jemalloc_prefork(void)
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@ -31,6 +44,10 @@ _malloc_prefork(void)
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#endif
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assert(malloc_initialized());
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#ifdef JEMALLOC_MUTEX_INIT_CB
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jemalloc_prefork_pid = getpid();
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#endif
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tsd = tsd_fetch();
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narenas = narenas_total_get();
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@ -105,6 +122,10 @@ _malloc_postfork(void)
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if (!malloc_initialized()) {
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return;
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}
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if (getpid() != jemalloc_prefork_pid) {
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jemalloc_postfork_child();
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return;
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}
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#endif
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assert(malloc_initialized());
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280
test/unit/fork.c
280
test/unit/fork.c
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@ -30,6 +30,60 @@ wait_for_child_exit(int pid) {
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}
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#endif
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#ifndef _WIN32
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static void
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create_arena(unsigned *arena_ind) {
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size_t sz = sizeof(*arena_ind);
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expect_d_eq(mallctl("arenas.create", (void *)arena_ind, &sz, NULL, 0),
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0, "Unexpected mallctl() failure");
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}
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static void
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bind_thread_arena(unsigned arena_ind) {
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unsigned old_arena_ind;
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size_t sz = sizeof(old_arena_ind);
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expect_d_eq(mallctl("thread.arena", (void *)&old_arena_ind, &sz,
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(void *)&arena_ind, sizeof(arena_ind)),
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0, "Unexpected mallctl() failure");
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}
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static void
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populate_tcache(void) {
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void *p[16];
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for (size_t i = 0; i < ARRAY_SIZE(p); i++) {
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p[i] = malloc(8);
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expect_ptr_not_null(p[i], "Unexpected malloc() failure");
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}
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for (size_t i = 0; i < ARRAY_SIZE(p); i++) {
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free(p[i]);
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}
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}
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static bool
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refresh_epoch(void) {
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uint64_t epoch = 1;
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return mallctl("epoch", NULL, NULL, &epoch, sizeof(epoch)) == 0;
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}
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static int
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read_arena_tcache_bytes(unsigned arena_ind, size_t *bytes) {
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char ctl[64];
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malloc_snprintf(ctl, sizeof(ctl),
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"stats.arenas.%u.tcache_bytes", arena_ind);
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size_t sz = sizeof(*bytes);
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return mallctl(ctl, bytes, &sz, NULL, 0);
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}
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static int
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read_arena_nthreads(unsigned arena_ind, unsigned *nthreads) {
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char ctl[64];
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malloc_snprintf(ctl, sizeof(ctl), "stats.arenas.%u.nthreads",
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arena_ind);
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size_t sz = sizeof(*nthreads);
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return mallctl(ctl, nthreads, &sz, NULL, 0);
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}
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#endif
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TEST_BEGIN(test_fork) {
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#ifndef _WIN32
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void *p;
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@ -292,8 +346,232 @@ TEST_BEGIN(test_fork_postfork_descriptor_relink) {
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}
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TEST_END
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#ifndef _WIN32
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typedef struct {
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unsigned arena_ind;
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atomic_b_t ready;
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atomic_b_t release;
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} fork_worker_arg_t;
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static void *
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fork_worker_thd(void *arg) {
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fork_worker_arg_t *worker = (fork_worker_arg_t *)arg;
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bind_thread_arena(worker->arena_ind);
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populate_tcache();
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atomic_store_b(&worker->ready, true, ATOMIC_RELEASE);
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while (!atomic_load_b(&worker->release, ATOMIC_ACQUIRE)) {
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sleep_ns(1000);
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}
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return NULL;
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}
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#endif
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TEST_BEGIN(test_fork_postfork_descriptor_relink_multithreaded) {
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#ifndef _WIN32
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test_skip_if(!config_stats);
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test_skip_if(!tcache_available(tsd_fetch()));
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unsigned survivor_arena;
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unsigned peer_arena;
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create_arena(&survivor_arena);
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create_arena(&peer_arena);
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bind_thread_arena(survivor_arena);
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populate_tcache();
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fork_worker_arg_t survivor_worker = {
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.arena_ind = survivor_arena,
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.ready = ATOMIC_INIT(false),
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.release = ATOMIC_INIT(false),
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};
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fork_worker_arg_t peer_worker = {
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.arena_ind = peer_arena,
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.ready = ATOMIC_INIT(false),
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.release = ATOMIC_INIT(false),
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};
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thd_t survivor_thd;
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thd_t peer_thd;
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thd_create(&survivor_thd, fork_worker_thd, &survivor_worker);
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thd_create(&peer_thd, fork_worker_thd, &peer_worker);
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while (!atomic_load_b(&survivor_worker.ready, ATOMIC_ACQUIRE)
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|| !atomic_load_b(&peer_worker.ready, ATOMIC_ACQUIRE)) {
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sleep_ns(1000);
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}
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expect_true(refresh_epoch(), "epoch refresh failed");
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size_t pre_survivor_bytes = 0;
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size_t pre_peer_bytes = 0;
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unsigned pre_survivor_nthreads = 0;
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unsigned pre_peer_nthreads = 0;
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expect_d_eq(read_arena_tcache_bytes(
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survivor_arena, &pre_survivor_bytes),
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0, "read survivor tcache_bytes pre-fork");
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expect_d_eq(read_arena_tcache_bytes(peer_arena, &pre_peer_bytes), 0,
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"read peer tcache_bytes pre-fork");
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expect_d_eq(read_arena_nthreads(
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survivor_arena, &pre_survivor_nthreads),
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0, "read survivor nthreads pre-fork");
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expect_d_eq(read_arena_nthreads(peer_arena, &pre_peer_nthreads), 0,
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"read peer nthreads pre-fork");
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expect_zu_gt(pre_survivor_bytes, 0,
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"Survivor arena should have cached bytes before fork");
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expect_zu_gt(pre_peer_bytes, 0,
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"Peer arena should have cached bytes before fork");
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expect_u_eq(pre_survivor_nthreads, 2,
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"Survivor arena should have two threads before fork");
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expect_u_eq(pre_peer_nthreads, 1,
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"Peer arena should have one thread before fork");
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pid_t pid = fork();
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if (pid == -1) {
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test_fail("Unexpected fork() failure");
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} else if (pid == 0) {
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if (!refresh_epoch()) {
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_exit(1);
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}
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size_t child_survivor_bytes = 0;
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size_t child_peer_bytes = 0;
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unsigned child_survivor_nthreads = 0;
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unsigned child_peer_nthreads = 0;
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if (read_arena_tcache_bytes(
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survivor_arena, &child_survivor_bytes) != 0) {
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_exit(2);
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}
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if (read_arena_tcache_bytes(peer_arena, &child_peer_bytes)
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!= 0) {
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_exit(3);
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}
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if (read_arena_nthreads(
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survivor_arena, &child_survivor_nthreads) != 0) {
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_exit(4);
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}
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if (read_arena_nthreads(peer_arena, &child_peer_nthreads)
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!= 0) {
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_exit(5);
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}
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if (child_survivor_nthreads != 1) {
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_exit(6);
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}
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if (child_peer_nthreads != 0) {
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_exit(7);
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}
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if (child_survivor_bytes == 0) {
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_exit(8);
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}
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/*
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* Don't compare child_survivor_bytes against pre_survivor_bytes:
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* on platforms where jemalloc is the default zone allocator
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* (macOS), internal allocations during the postfork handler
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* (e.g. pthread_mutex_init) can inflate the surviving thread's
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* tcache, making the child's bytes >= the pre-fork total.
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*/
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if (child_peer_bytes != 0) {
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_exit(9);
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}
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_exit(0);
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} else {
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wait_for_child_exit(pid);
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}
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expect_true(refresh_epoch(), "epoch refresh failed");
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size_t parent_survivor_bytes = 0;
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size_t parent_peer_bytes = 0;
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unsigned parent_survivor_nthreads = 0;
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unsigned parent_peer_nthreads = 0;
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expect_d_eq(read_arena_tcache_bytes(
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survivor_arena, &parent_survivor_bytes),
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0, "read survivor tcache_bytes post-fork");
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expect_d_eq(read_arena_tcache_bytes(peer_arena, &parent_peer_bytes), 0,
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"read peer tcache_bytes post-fork");
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expect_d_eq(read_arena_nthreads(
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survivor_arena, &parent_survivor_nthreads),
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0, "read survivor nthreads post-fork");
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expect_d_eq(read_arena_nthreads(peer_arena, &parent_peer_nthreads), 0,
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"read peer nthreads post-fork");
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expect_zu_eq(parent_survivor_bytes, pre_survivor_bytes,
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"Parent survivor arena cached bytes should be unchanged");
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expect_zu_eq(parent_peer_bytes, pre_peer_bytes,
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"Parent peer arena cached bytes should be unchanged");
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expect_u_eq(parent_survivor_nthreads, 2,
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"Parent survivor arena should still have two threads");
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expect_u_eq(parent_peer_nthreads, 1,
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"Parent peer arena should still have one thread");
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atomic_store_b(&survivor_worker.release, true, ATOMIC_RELEASE);
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atomic_store_b(&peer_worker.release, true, ATOMIC_RELEASE);
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thd_join(survivor_thd, NULL);
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thd_join(peer_thd, NULL);
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#else
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test_skip("fork(2) is irrelevant to Windows");
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#endif
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}
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TEST_END
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TEST_BEGIN(test_fork_postfork_double_fork) {
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#ifndef _WIN32
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test_skip_if(!config_stats);
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unsigned arena_ind;
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create_arena(&arena_ind);
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bind_thread_arena(arena_ind);
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populate_tcache();
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pid_t pid = fork();
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if (pid == -1) {
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test_fail("Unexpected fork() failure");
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} else if (pid == 0) {
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/* First child: verify nthreads, then fork again. */
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if (!refresh_epoch()) {
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_exit(1);
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}
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unsigned nthreads = 0;
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if (read_arena_nthreads(arena_ind, &nthreads) != 0) {
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_exit(2);
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}
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if (nthreads != 1) {
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_exit(3);
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}
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pid_t pid2 = fork();
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if (pid2 == -1) {
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_exit(4);
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} else if (pid2 == 0) {
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/* Grandchild: verify nthreads again. */
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if (!refresh_epoch()) {
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_exit(1);
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}
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unsigned gc_nthreads = 0;
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if (read_arena_nthreads(arena_ind, &gc_nthreads)
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!= 0) {
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_exit(2);
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}
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if (gc_nthreads != 1) {
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_exit(3);
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}
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_exit(0);
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} else {
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wait_for_child_exit(pid2);
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}
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_exit(0);
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} else {
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wait_for_child_exit(pid);
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}
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#else
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test_skip("fork(2) is irrelevant to Windows");
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#endif
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}
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TEST_END
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int
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main(void) {
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return test_no_reentrancy(test_fork, test_fork_child_usability,
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test_fork_multithreaded, test_fork_postfork_descriptor_relink);
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test_fork_multithreaded, test_fork_postfork_descriptor_relink,
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test_fork_postfork_descriptor_relink_multithreaded,
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test_fork_postfork_double_fork);
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}
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