From 703fbc0ff584e00899b5b30aa927c55ecc89dabf Mon Sep 17 00:00:00 2001
From: David Goldblatt <davidgoldblatt@fb.com>
Date: Mon, 2 Dec 2019 16:45:40 -0800
Subject: [PATCH] Introduce unsafe reentrancy guards.

We have to work to circumvent the safety checks in pre_reentrancy when going
down extent hook pathways.  Instead, let's explicitly have checked and unchecked
guards.
---
 .../internal/jemalloc_internal_inlines_a.h    | 16 ++----------
 include/jemalloc/internal/tsd.h               | 26 +++++++++++++++++++
 2 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/include/jemalloc/internal/jemalloc_internal_inlines_a.h b/include/jemalloc/internal/jemalloc_internal_inlines_a.h
index fedbd862..98a64780 100644
--- a/include/jemalloc/internal/jemalloc_internal_inlines_a.h
+++ b/include/jemalloc/internal/jemalloc_internal_inlines_a.h
@@ -151,24 +151,12 @@ static inline void
 pre_reentrancy(tsd_t *tsd, arena_t *arena) {
 	/* arena is the current context.  Reentry from a0 is not allowed. */
 	assert(arena != arena_get(tsd_tsdn(tsd), 0, false));
-
-	bool fast = tsd_fast(tsd);
-	assert(tsd_reentrancy_level_get(tsd) < INT8_MAX);
-	++*tsd_reentrancy_levelp_get(tsd);
-	if (fast) {
-		/* Prepare slow path for reentrancy. */
-		tsd_slow_update(tsd);
-		assert(tsd_state_get(tsd) == tsd_state_nominal_slow);
-	}
+	tsd_pre_reentrancy_raw(tsd);
 }
 
 static inline void
 post_reentrancy(tsd_t *tsd) {
-	int8_t *reentrancy_level = tsd_reentrancy_levelp_get(tsd);
-	assert(*reentrancy_level > 0);
-	if (--*reentrancy_level == 0) {
-		tsd_slow_update(tsd);
-	}
+	tsd_post_reentrancy_raw(tsd);
 }
 
 #endif /* JEMALLOC_INTERNAL_INLINES_A_H */
diff --git a/include/jemalloc/internal/tsd.h b/include/jemalloc/internal/tsd.h
index b7ce7ca2..3465a2d4 100644
--- a/include/jemalloc/internal/tsd.h
+++ b/include/jemalloc/internal/tsd.h
@@ -446,4 +446,30 @@ tsd_state_nocleanup(tsd_t *tsd) {
 	    tsd_state_get(tsd) == tsd_state_minimal_initialized;
 }
 
+/*
+ * These "raw" tsd reentrancy functions don't have any debug checking to make
+ * sure that we're not touching arena 0.  Better is to call pre_reentrancy and
+ * post_reentrancy if this is possible.
+ */
+static inline void
+tsd_pre_reentrancy_raw(tsd_t *tsd) {
+	bool fast = tsd_fast(tsd);
+	assert(tsd_reentrancy_level_get(tsd) < INT8_MAX);
+	++*tsd_reentrancy_levelp_get(tsd);
+	if (fast) {
+		/* Prepare slow path for reentrancy. */
+		tsd_slow_update(tsd);
+		assert(tsd_state_get(tsd) == tsd_state_nominal_slow);
+	}
+}
+
+static inline void
+tsd_post_reentrancy_raw(tsd_t *tsd) {
+	int8_t *reentrancy_level = tsd_reentrancy_levelp_get(tsd);
+	assert(*reentrancy_level > 0);
+	if (--*reentrancy_level == 0) {
+		tsd_slow_update(tsd);
+	}
+}
+
 #endif /* JEMALLOC_INTERNAL_TSD_H */