Switch to fine-grained reentrancy support.

Previously we had a general detection and support of reentrancy, at the cost of
having branches and inc / dec operations on fast paths.  To avoid taxing fast
paths, we move the reentrancy operations onto tsd slow state, and only modify
reentrancy level around external calls (that might trigger reentrancy).

3 files changed, 55 insertions, 76 deletions

diff --git a/src/arena.c b/src/arena.c
index 4f5dcf6..5b540ce 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -1966,11 +1966,9 @@ arena_new(tsdn_t *tsdn, unsigned ind, extent_hooks_t *extent_hooks) {
 		 * If we're here, then arena 0 already exists, so bootstrapping
 		 * is done enough that we should have tsd.
 		 */
-		int8_t *reentrancy_level = tsd_reentrancy_levelp_get(tsdn_tsd(
-		    tsdn));
-		++*reentrancy_level;
+		pre_reentrancy(tsdn_tsd(tsdn));
 		hooks_arena_new_hook();
-		--*reentrancy_level;
+		post_reentrancy(tsdn_tsd(tsdn));
 	}
 
 	return arena;
diff --git a/src/jemalloc.c b/src/jemalloc.c
index 4bec2de..4c38517 100644
--- a/src/jemalloc.c
+++ b/src/jemalloc.c
@@ -1663,13 +1663,8 @@ imalloc_body(static_opts_t *sopts, dynamic_opts_t *dopts, tsd_t *tsd) {
 	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.
-	 */
-	int8_t *reentrancy_level = NULL;
+	/* Reentrancy is only checked on slow path. */
+	int8_t reentrancy_level;
 
 	/* Compute the amount of memory the user wants. */
 	if (unlikely(compute_size_with_overflow(sopts->may_overflow, dopts,
@@ -1716,12 +1711,11 @@ imalloc_body(static_opts_t *sopts, dynamic_opts_t *dopts, tsd_t *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) {
+	reentrancy_level = tsd_reentrancy_level_get(tsd);
+	if (reentrancy_level == 0) {
 		witness_assert_lockless(tsd_tsdn(tsd));
 	}
-	if (unlikely(*reentrancy_level > 1)) {
+	if (sopts->slow && unlikely(reentrancy_level > 0)) {
 		/*
 		 * We should never specify particular arenas or tcaches from
 		 * within our internal allocations.
@@ -1795,14 +1789,9 @@ imalloc_body(static_opts_t *sopts, dynamic_opts_t *dopts, tsd_t *tsd) {
 	}
 
 	/* Success! */
-	if (*reentrancy_level == 1) {
+	if (reentrancy_level == 0) {
 		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;
 
@@ -1826,10 +1815,6 @@ label_oom:
 		*dopts->result = NULL;
 	}
 
-	if (reentrancy_level != NULL) {
-		--*reentrancy_level;
-	}
-
 	return ENOMEM;
 
 	/*
@@ -1857,10 +1842,6 @@ label_invalid_alignment:
 		*dopts->result = NULL;
 	}
 
-	if (reentrancy_level != NULL) {
-		--*reentrancy_level;
-	}
-
 	return EINVAL;
 }
 
@@ -2053,8 +2034,11 @@ 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) {
-	if (*tsd_reentrancy_levelp_get(tsd) == 0) {
+	assert(slow_path || tsd_assert_fast(tsd));
+	if (tsd_reentrancy_level_get(tsd) == 0) {
 		witness_assert_lockless(tsd_tsdn(tsd));
+	} else {
+		assert(slow_path);
 	}
 
 	assert(ptr != NULL);
@@ -2088,8 +2072,11 @@ 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) {
-	if (*tsd_reentrancy_levelp_get(tsd) == 0) {
+	assert(slow_path || tsd_assert_fast(tsd));
+	if (tsd_reentrancy_level_get(tsd) == 0) {
 		witness_assert_lockless(tsd_tsdn(tsd));
+	} else {
+		assert(slow_path);
 	}
 
 	assert(ptr != NULL);
@@ -2129,14 +2116,14 @@ je_realloc(void *ptr, size_t size) {
 
 	if (unlikely(size == 0)) {
 		if (ptr != NULL) {
-			tsd_t *tsd;
-
 			/* realloc(ptr, 0) is equivalent to free(ptr). */
 			UTRACE(ptr, 0, 0);
-			tsd = tsd_fetch();
-			tcache_t *tcache = NULL;
-			if (likely(*tsd_reentrancy_levelp_get(tsd) == 0)) {
+			tcache_t *tcache;
+			tsd_t *tsd = tsd_fetch();
+			if (tsd_reentrancy_level_get(tsd) == 0) {
 				tcache = tcache_get(tsd);
+			} else {
+				tcache = NULL;
 			}
 			ifree(tsd, ptr, tcache, true);
 			return NULL;
@@ -2200,29 +2187,25 @@ je_free(void *ptr) {
 	UTRACE(ptr, 0, 0);
 	if (likely(ptr != NULL)) {
 		tsd_t *tsd = tsd_fetch();
-		if (*tsd_reentrancy_levelp_get(tsd) == 0) {
+		if (tsd_reentrancy_level_get(tsd) == 0) {
 			witness_assert_lockless(tsd_tsdn(tsd));
 		}
+
 		tcache_t *tcache;
 		if (likely(tsd_fast(tsd))) {
 			tsd_assert_fast(tsd);
-			if (likely(*tsd_reentrancy_levelp_get(tsd) == 0)) {
-				/* Getting tcache ptr unconditionally. */
-				tcache = tsd_tcachep_get(tsd);
-				assert(tcache == tcache_get(tsd));
-			} else {
-				tcache = NULL;
-			}
+			/* Unconditionally get tcache ptr on fast path. */
+			tcache = tsd_tcachep_get(tsd);
 			ifree(tsd, ptr, tcache, false);
 		} else {
-			if (likely(*tsd_reentrancy_levelp_get(tsd) == 0)) {
+			if (likely(tsd_reentrancy_level_get(tsd) == 0)) {
 				tcache = tcache_get(tsd);
 			} else {
 				tcache = NULL;
 			}
 			ifree(tsd, ptr, tcache, true);
 		}
-		if (*tsd_reentrancy_levelp_get(tsd) == 0) {
+		if (tsd_reentrancy_level_get(tsd) == 0) {
 			witness_assert_lockless(tsd_tsdn(tsd));
 		}
 	}
@@ -2707,33 +2690,32 @@ je_sallocx(const void *ptr, int flags) {
 
 JEMALLOC_EXPORT void JEMALLOC_NOTHROW
 je_dallocx(void *ptr, int flags) {
-	tsd_t *tsd;
-	tcache_t *tcache;
-
 	assert(ptr != NULL);
 	assert(malloc_initialized() || IS_INITIALIZER);
 
-	tsd = tsd_fetch();
+	tsd_t *tsd = tsd_fetch();
 	bool fast = tsd_fast(tsd);
 	witness_assert_lockless(tsd_tsdn(tsd));
+
+	tcache_t *tcache;
 	if (unlikely((flags & MALLOCX_TCACHE_MASK) != 0)) {
 		/* Not allowed to be reentrant and specify a custom tcache. */
-		assert(*tsd_reentrancy_levelp_get(tsd) == 0);
+		assert(tsd_reentrancy_level_get(tsd) == 0);
 		if ((flags & MALLOCX_TCACHE_MASK) == MALLOCX_TCACHE_NONE) {
 			tcache = NULL;
 		} else {
 			tcache = tcaches_get(tsd, MALLOCX_TCACHE_GET(flags));
 		}
 	} else {
-		if (likely(*tsd_reentrancy_levelp_get(tsd) == 0)) {
-			if (likely(fast)) {
-				tcache = tsd_tcachep_get(tsd);
-				assert(tcache == tcache_get(tsd));
-			} else {
+		if (likely(fast)) {
+			tcache = tsd_tcachep_get(tsd);
+			assert(tcache == tcache_get(tsd));
+		} else {
+			if (likely(tsd_reentrancy_level_get(tsd) == 0)) {
 				tcache = tcache_get(tsd);
+			}  else {
+				tcache = NULL;
 			}
-		} else {
-			tcache = NULL;
 		}
 	}
 
@@ -2749,10 +2731,9 @@ je_dallocx(void *ptr, int flags) {
 
 JEMALLOC_ALWAYS_INLINE_C size_t
 inallocx(tsdn_t *tsdn, size_t size, int flags) {
-	size_t usize;
-
 	witness_assert_lockless(tsdn);
 
+	size_t usize;
 	if (likely((flags & MALLOCX_LG_ALIGN_MASK) == 0)) {
 		usize = s2u(size);
 	} else {
@@ -2764,36 +2745,34 @@ inallocx(tsdn_t *tsdn, size_t size, int flags) {
 
 JEMALLOC_EXPORT void JEMALLOC_NOTHROW
 je_sdallocx(void *ptr, size_t size, int flags) {
-	tsd_t *tsd;
-	size_t usize;
-	tcache_t *tcache;
-
 	assert(ptr != NULL);
 	assert(malloc_initialized() || IS_INITIALIZER);
-	tsd = tsd_fetch();
+
+	tsd_t *tsd = tsd_fetch();
 	bool fast = tsd_fast(tsd);
-	usize = inallocx(tsd_tsdn(tsd), size, flags);
+	size_t usize = inallocx(tsd_tsdn(tsd), size, flags);
 	assert(usize == isalloc(tsd_tsdn(tsd), ptr));
-
 	witness_assert_lockless(tsd_tsdn(tsd));
+
+	tcache_t *tcache;
 	if (unlikely((flags & MALLOCX_TCACHE_MASK) != 0)) {
 		/* Not allowed to be reentrant and specify a custom tcache. */
-		assert(*tsd_reentrancy_levelp_get(tsd) == 0);
+		assert(tsd_reentrancy_level_get(tsd) == 0);
 		if ((flags & MALLOCX_TCACHE_MASK) == MALLOCX_TCACHE_NONE) {
 			tcache = NULL;
 		} else {
 			tcache = tcaches_get(tsd, MALLOCX_TCACHE_GET(flags));
 		}
 	} else {
-		if (likely(*tsd_reentrancy_levelp_get(tsd) == 0)) {
-			if (likely(fast)) {
-				tcache = tsd_tcachep_get(tsd);
-				assert(tcache == tcache_get(tsd));
-			} else {
+		if (likely(fast)) {
+			tcache = tsd_tcachep_get(tsd);
+			assert(tcache == tcache_get(tsd));
+		} else {
+			if (likely(tsd_reentrancy_level_get(tsd) == 0)) {
 				tcache = tcache_get(tsd);
+			} else {
+				tcache = NULL;
 			}
-		} else {
-			tcache = NULL;
 		}
 	}
 
diff --git a/src/tsd.c b/src/tsd.c
index bdd3f3c..cb7dd3f 100644
--- a/src/tsd.c
+++ b/src/tsd.c
@@ -15,7 +15,8 @@ malloc_tsd_data(, , tsd_t, TSD_INITIALIZER)
 void
 tsd_slow_update(tsd_t *tsd) {
 	if (tsd_nominal(tsd)) {
-		if (malloc_slow || !tsd->tcache_enabled) {
+		if (malloc_slow || !tsd->tcache_enabled ||
+		    tsd_reentrancy_level_get(tsd) > 0) {
 			tsd->state = tsd_state_nominal_slow;
 		} else {
 			tsd->state = tsd_state_nominal;
@@ -28,6 +29,7 @@ tsd_fetch_slow(tsd_t *tsd) {
 	if (tsd->state == tsd_state_nominal_slow) {
 		/* On slow path but no work needed. */
 		assert(malloc_slow || !tsd_tcache_enabled_get(tsd) ||
+		    tsd_reentrancy_level_get(tsd) > 0 ||
 		    *tsd_arenas_tdata_bypassp_get(tsd));
 	} else if (tsd->state == tsd_state_uninitialized) {
 		tsd->state = tsd_state_nominal;