Add basic reentrancy-checking support, and allow arena_new to reenter.

This checks whether or not we're reentrant using thread-local data, and, if we
are, moves certain internal allocations to use arena 0 (which should be properly
initialized after bootstrapping).

The immediate thing this allows is spinning up threads in arena_new, which will
enable spinning up background threads there.

include/jemalloc/internal/hooks.h

@@ -1,8 +1,8 @@
 #ifndef JEMALLOC_INTERNAL_HOOKS_H
 #define JEMALLOC_INTERNAL_HOOKS_H
 
-extern void (*hooks_arena_new_hook)();
-extern void (*hooks_libc_hook)();
+extern JEMALLOC_EXPORT void (*hooks_arena_new_hook)();
+extern JEMALLOC_EXPORT void (*hooks_libc_hook)();
 
 #define JEMALLOC_HOOK(fn, hook) ((void)(hook != NULL && (hook(), 0)), fn)
 

include/jemalloc/internal/jemalloc_internal.h.in

@@ -1013,6 +1013,11 @@ arena_choose_impl(tsd_t *tsd, arena_t *arena, bool internal) {
 		return arena;
 	}
 
+	/* During reentrancy, arena 0 is the safest bet. */
+	if (*tsd_reentrancy_levelp_get(tsd) > 1) {
+		return arena_get(tsd_tsdn(tsd), 0, true);
+	}
+
 	ret = internal ? tsd_iarena_get(tsd) : tsd_arena_get(tsd);
 	if (unlikely(ret == NULL)) {
 		ret = arena_choose_hard(tsd, internal);
@@ -1193,7 +1198,9 @@ idalloctm(tsdn_t *tsdn, void *ptr, tcache_t *tcache, bool is_internal,
 	if (config_stats && is_internal) {
 		arena_internal_sub(iaalloc(tsdn, ptr), isalloc(tsdn, ptr));
 	}
-
+	if (!is_internal && *tsd_reentrancy_levelp_get(tsdn_tsd(tsdn)) != 0) {
+		tcache = NULL;
+	}
 	arena_dalloc(tsdn, ptr, tcache, slow_path);
 }
 

include/jemalloc/internal/private_symbols.txt

@@ -232,6 +232,7 @@ hash_rotl_64
 hash_x64_128
 hash_x86_128
 hash_x86_32
+hooks_arena_new_hook
 hooks_libc_hook
 iaalloc
 ialloc
@@ -537,6 +538,9 @@ tsd_init_head
 tsd_narenas_tdata_get
 tsd_narenas_tdata_set
 tsd_narenas_tdatap_get
+tsd_reentrancy_level_get
+tsd_reentrancy_level_set
+tsd_reentrancy_levelp_get
 tsd_wrapper_get
 tsd_wrapper_set
 tsd_nominal

include/jemalloc/internal/tsd_structs.h

@@ -65,7 +65,8 @@ struct tsd_init_head_s {
     O(witnesses,		witness_list_t,	no,	no,	yes)	\
     O(rtree_leaf_elm_witnesses,	rtree_leaf_elm_witness_tsd_t,		\
 						no,	no,	no)	\
-    O(witness_fork,		bool,		yes,	no,	no)
+    O(witness_fork,		bool,		yes,	no,	no)	\
+    O(reentrancy_level,		int,		no,	no,	no)
 
 #define TSD_INITIALIZER {						\
     tsd_state_uninitialized,						\
@@ -82,7 +83,8 @@ struct tsd_init_head_s {
     TCACHE_ZERO_INITIALIZER,						\
     ql_head_initializer(witnesses),					\
     RTREE_ELM_WITNESS_TSD_INITIALIZER,					\
-    false								\
+    false,								\
+    0									\
 }
 
 struct tsd_s {

src/arena.c

@@ -1952,6 +1952,19 @@ arena_new(tsdn_t *tsdn, unsigned ind, extent_hooks_t *extent_hooks) {
 
 	arena->base = base;
 
+	/* We don't support reetrancy for arena 0 bootstrapping. */
+	if (ind != 0 && hooks_arena_new_hook) {
+		/*
+		 * If we're here, then arena 0 already exists, so bootstrapping
+		 * is done enough that we should have tsd.
+		 */
+		int *reentrancy_level = tsd_reentrancy_levelp_get(tsdn_tsd(
+		    tsdn));
+		++*reentrancy_level;
+		hooks_arena_new_hook();
+		--*reentrancy_level;
+	}
+
 	return arena;
 label_error:
 	if (ind != 0) {

src/jemalloc.c

@@ -1656,6 +1656,14 @@ imalloc_body(static_opts_t *sopts, dynamic_opts_t *dopts) {
 	szind_t ind = 0;
 	size_t usize = 0;
 
+	/*
+	 * For reentrancy checking, we get the old reentrancy level from tsd and
+	 * reset it once we're done.  In case of early bailout though, we never
+	 * bother getting the old level, so we shouldn't try to reset it.  This
+	 * is indicated by leaving the pointer as NULL.
+	 */
+	int *reentrancy_level = NULL;
+
 	/* Initialize (if we can't prove we don't have to). */
 	if (sopts->slow) {
 		if (unlikely(malloc_init())) {
@@ -1708,7 +1716,27 @@ imalloc_body(static_opts_t *sopts, dynamic_opts_t *dopts) {
 	 * some reason.  Let's grab it right away.
 	 */
 	tsd = tsd_fetch();
-	witness_assert_lockless(tsd_tsdn(tsd));
+
+	/*
+	 * If we need to handle reentrancy, we can do it out of a
+	 * known-initialized arena (i.e. arena 0).
+	 */
+	reentrancy_level = tsd_reentrancy_levelp_get(tsd);
+	++*reentrancy_level;
+	if (*reentrancy_level == 1) {
+		witness_assert_lockless(tsd_tsdn(tsd));
+	}
+	if (unlikely(*reentrancy_level > 1)) {
+		/*
+		 * We should never specify particular arenas or tcaches from
+		 * within our internal allocations.
+		 */
+		assert(dopts->tcache_ind == TCACHE_IND_AUTOMATIC);
+		assert(dopts->arena_ind = ARENA_IND_AUTOMATIC);
+		dopts->tcache_ind = TCACHE_IND_NONE;
+		/* We know that arena 0 has already been initialized. */
+		dopts->arena_ind = 0;
+	}
 
 	/* If profiling is on, get our profiling context. */
 	if (config_prof && opt_prof) {
@@ -1769,9 +1797,15 @@ imalloc_body(static_opts_t *sopts, dynamic_opts_t *dopts) {
 		UTRACE(0, size, allocation);
 	}
 
-	witness_assert_lockless(tsd_tsdn(tsd));
-
 	/* Success! */
+	if (*reentrancy_level == 1) {
+		witness_assert_lockless(tsd_tsdn(tsd));
+	}
+	/*
+	 * If we got here, we never bailed out on a failure path, so
+	 * reentrancy_level is non-null.
+	 */
+	--*reentrancy_level;
 	*dopts->result = allocation;
 	return 0;
 
@@ -1795,6 +1829,10 @@ label_oom:
 		*dopts->result = NULL;
 	}
 
+	if (reentrancy_level != NULL) {
+		--*reentrancy_level;
+	}
+
 	return ENOMEM;
 
 	/*
@@ -1822,6 +1860,10 @@ label_invalid_alignment:
 		*dopts->result = NULL;
 	}
 
+	if (reentrancy_level != NULL) {
+		--*reentrancy_level;
+	}
+
 	return EINVAL;
 }
 
@@ -1996,7 +2038,9 @@ irealloc_prof(tsd_t *tsd, void *old_ptr, size_t old_usize, size_t usize) {
 
 JEMALLOC_ALWAYS_INLINE_C void
 ifree(tsd_t *tsd, void *ptr, tcache_t *tcache, bool slow_path) {
-	witness_assert_lockless(tsd_tsdn(tsd));
+	if (*tsd_reentrancy_levelp_get(tsd) == 0) {
+		witness_assert_lockless(tsd_tsdn(tsd));
+	}
 
 	assert(ptr != NULL);
 	assert(malloc_initialized() || IS_INITIALIZER);
@@ -2021,7 +2065,9 @@ ifree(tsd_t *tsd, void *ptr, tcache_t *tcache, bool slow_path) {
 
 JEMALLOC_ALWAYS_INLINE_C void
 isfree(tsd_t *tsd, void *ptr, size_t usize, tcache_t *tcache, bool slow_path) {
-	witness_assert_lockless(tsd_tsdn(tsd));
+	if (*tsd_reentrancy_levelp_get(tsd) == 0) {
+		witness_assert_lockless(tsd_tsdn(tsd));
+	}
 
 	assert(ptr != NULL);
 	assert(malloc_initialized() || IS_INITIALIZER);
@@ -2056,7 +2102,11 @@ je_realloc(void *ptr, size_t size) {
 			/* realloc(ptr, 0) is equivalent to free(ptr). */
 			UTRACE(ptr, 0, 0);
 			tsd = tsd_fetch();
-			ifree(tsd, ptr, tcache_get(tsd), true);
+			tcache_t *tcache = NULL;
+			if (likely(*tsd_reentrancy_levelp_get(tsd) == 0)) {
+				tcache = tcache_get(tsd);
+			}
+			ifree(tsd, ptr, tcache, true);
 			return NULL;
 		}
 		size = 1;
@@ -2111,13 +2161,21 @@ je_free(void *ptr) {
 	UTRACE(ptr, 0, 0);
 	if (likely(ptr != NULL)) {
 		tsd_t *tsd = tsd_fetch();
-		witness_assert_lockless(tsd_tsdn(tsd));
-		if (likely(!malloc_slow)) {
-			ifree(tsd, ptr, tcache_get(tsd), false);
-		} else {
-			ifree(tsd, ptr, tcache_get(tsd), true);
+		if (*tsd_reentrancy_levelp_get(tsd) == 0) {
+			witness_assert_lockless(tsd_tsdn(tsd));
+		}
+		tcache_t *tcache = NULL;
+		if (likely(*tsd_reentrancy_levelp_get(tsd) == 0)) {
+			tcache = tcache_get(tsd);
+		}
+		if (likely(!malloc_slow)) {
+			ifree(tsd, ptr, tcache, false);
+		} else {
+			ifree(tsd, ptr, tcache, true);
+		}
+		if (*tsd_reentrancy_levelp_get(tsd) == 0) {
+			witness_assert_lockless(tsd_tsdn(tsd));
 		}
-		witness_assert_lockless(tsd_tsdn(tsd));
 	}
 }
 
@@ -2599,13 +2657,19 @@ je_dallocx(void *ptr, int flags) {
 	tsd = tsd_fetch();
 	witness_assert_lockless(tsd_tsdn(tsd));
 	if (unlikely((flags & MALLOCX_TCACHE_MASK) != 0)) {
+		/* Not allowed to be reentrant and specify a custom tcache. */
+		assert(*tsd_reentrancy_levelp_get(tsd) == 0);
 		if ((flags & MALLOCX_TCACHE_MASK) == MALLOCX_TCACHE_NONE) {
 			tcache = NULL;
 		} else {
 			tcache = tcaches_get(tsd, MALLOCX_TCACHE_GET(flags));
 		}
 	} else {
-		tcache = tcache_get(tsd);
+		if (likely(*tsd_reentrancy_levelp_get(tsd) == 0)) {
+			tcache = tcache_get(tsd);
+		} else {
+			tcache = NULL;
+		}
 	}
 
 	UTRACE(ptr, 0, 0);
@@ -2646,13 +2710,19 @@ je_sdallocx(void *ptr, size_t size, int flags) {
 
 	witness_assert_lockless(tsd_tsdn(tsd));
 	if (unlikely((flags & MALLOCX_TCACHE_MASK) != 0)) {
+		/* Not allowed to be reentrant and specify a custom tcache. */
+		assert(*tsd_reentrancy_levelp_get(tsd) == 0);
 		if ((flags & MALLOCX_TCACHE_MASK) == MALLOCX_TCACHE_NONE) {
 			tcache = NULL;
 		} else {
 			tcache = tcaches_get(tsd, MALLOCX_TCACHE_GET(flags));
 		}
 	} else {
-		tcache = tcache_get(tsd);
+		if (likely(*tsd_reentrancy_levelp_get(tsd) == 0)) {
+			tcache = tcache_get(tsd);
+		} else {
+			tcache = NULL;
+		}
 	}
 
 	UTRACE(ptr, 0, 0);

test/src/test.c

@@ -10,31 +10,56 @@ static const char *	test_name = "";
 /* Reentrancy testing helpers. */
 
 #define NUM_REENTRANT_ALLOCS 20
-static bool reentrant = false;
-static bool hook_ran = false;
-static void *to_free[NUM_REENTRANT_ALLOCS];
+typedef enum {
+	non_reentrant = 0,
+	libc_reentrant = 1,
+	arena_new_reentrant = 2
+} reentrancy_t;
+static reentrancy_t reentrancy;
+
+static bool libc_hook_ran = false;
+static bool arena_new_hook_ran = false;
+
+static const char *
+reentrancy_t_str(reentrancy_t r) {
+	switch (r) {
+	case non_reentrant:
+		return "non-reentrant";
+	case libc_reentrant:
+		return "libc-reentrant";
+	case arena_new_reentrant:
+		return "arena_new-reentrant";
+	default:
+		unreachable();
+	}
+}
 
 static void
-reentrancy_hook() {
-	hook_ran = true;
-	hooks_libc_hook = NULL;
+do_hook(bool *hook_ran, void (**hook)()) {
+	*hook_ran = true;
+	*hook = NULL;
 
-	void *to_free_local[NUM_REENTRANT_ALLOCS];
 	size_t alloc_size = 1;
 	for (int i = 0; i < NUM_REENTRANT_ALLOCS; i++) {
-		to_free[i] = malloc(alloc_size);
-		to_free_local[i] = malloc(alloc_size);
+		free(malloc(alloc_size));
 		alloc_size *= 2;
 	}
-	for (int i = 0; i < NUM_REENTRANT_ALLOCS; i++) {
-		free(to_free_local[i]);
-	}
+}
+
+static void
+libc_reentrancy_hook() {
+	do_hook(&libc_hook_ran, &hooks_libc_hook);
+}
+
+static void
+arena_new_reentrancy_hook() {
+	do_hook(&arena_new_hook_ran, &hooks_arena_new_hook);
 }
 
 /* Actual test infrastructure. */
 bool
 test_is_reentrant() {
-	return reentrant;
+	return reentrancy != non_reentrant;
 }
 
 JEMALLOC_FORMAT_PRINTF(1, 2)
@@ -81,9 +106,8 @@ p_test_init(const char *name) {
 void
 p_test_fini(void) {
 	test_counts[test_status]++;
-	malloc_printf("%s: %s (%s)\n", test_name,
-	    test_status_string(test_status),
-	    reentrant ? "reentrant" : "non-reentrant");
+	malloc_printf("%s (%s): %s\n", test_name, reentrancy_t_str(reentrancy),
+	    test_status_string(test_status));
 }
 
 static test_status_t
@@ -106,24 +130,28 @@ p_test_impl(bool do_malloc_init, bool do_reentrant, test_t *t, va_list ap) {
 	ret = test_status_pass;
 	for (; t != NULL; t = va_arg(ap, test_t *)) {
 		/* Non-reentrant run. */
-		reentrant = false;
+		reentrancy = non_reentrant;
+		hooks_arena_new_hook = hooks_libc_hook = NULL;
 		t();
 		if (test_status > ret) {
 			ret = test_status;
 		}
 		/* Reentrant run. */
 		if (do_reentrant) {
-			reentrant = true;
-			hooks_libc_hook = &reentrancy_hook;
+			reentrancy = libc_reentrant;
+			hooks_arena_new_hook = NULL;
+			hooks_libc_hook = &libc_reentrancy_hook;
 			t();
 			if (test_status > ret) {
 				ret = test_status;
 			}
-			if (hook_ran) {
-				hook_ran = false;
-				for (int i = 0; i < NUM_REENTRANT_ALLOCS; i++) {
-					free(to_free[i]);
-				}
+
+			reentrancy = arena_new_reentrant;
+			hooks_libc_hook = NULL;
+			hooks_arena_new_hook = &arena_new_reentrancy_hook;
+			t();
+			if (test_status > ret) {
+				ret = test_status;
 			}
 		}
 	}

test/stress/microbench.c

@@ -156,7 +156,7 @@ TEST_END
 
 int
 main(void) {
-	return test(
+	return test_no_reentrancy(
 	    test_malloc_vs_mallocx,
 	    test_free_vs_dallocx,
 	    test_dallocx_vs_sdallocx,

test/unit/stats.c

@@ -351,7 +351,7 @@ TEST_END
 
 int
 main(void) {
-	return test(
+	return test_no_reentrancy(
 	    test_stats_summary,
 	    test_stats_large,
 	    test_stats_arenas_summary,

test/unit/tsd.c

@@ -79,7 +79,6 @@ thd_start(void *arg) {
 }
 
 TEST_BEGIN(test_tsd_main_thread) {
-	test_skip_if(test_is_reentrant());
 	thd_start((void *)(uintptr_t)0xa5f3e329);
 }
 TEST_END
@@ -144,7 +143,7 @@ main(void) {
 	data_tsd_boot();
 	data_test_started = true;
 
-	return test(
+	return test_no_reentrancy(
 	    test_tsd_main_thread,
 	    test_tsd_sub_thread,
 	    test_tsd_reincarnation);