From 19a51abf337d35b3bdbbac22d8c513f4fd8b6c57 Mon Sep 17 00:00:00 2001
From: Qi Wang <interwq@gwu.edu>
Date: Mon, 4 Nov 2019 16:44:37 -0800
Subject: [PATCH] Avoid arena->offset_state when tsd not available for prng.

Use stack locals and remove the offset_state in arena.
---
 include/jemalloc/internal/arena_structs.h |  8 --------
 src/arena.c                               | 12 ------------
 src/extent.c                              |  4 ++--
 3 files changed, 2 insertions(+), 22 deletions(-)

diff --git a/include/jemalloc/internal/arena_structs.h b/include/jemalloc/internal/arena_structs.h
index 54889dc8..bc8c0394 100644
--- a/include/jemalloc/internal/arena_structs.h
+++ b/include/jemalloc/internal/arena_structs.h
@@ -118,14 +118,6 @@ struct arena_s {
 	/* Synchronization: internal. */
 	prof_accum_t		prof_accum;
 
-	/*
-	 * PRNG state for cache index randomization of large allocation base
-	 * pointers.
-	 *
-	 * Synchronization: atomic.
-	 */
-	atomic_zu_t		offset_state;
-
 	/*
 	 * Extent serial number generator state.
 	 *
diff --git a/src/arena.c b/src/arena.c
index e4dd4770..fa18d144 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -1981,18 +1981,6 @@ arena_new(tsdn_t *tsdn, unsigned ind, extent_hooks_t *extent_hooks) {
 		}
 	}
 
-	if (config_cache_oblivious) {
-		/*
-		 * A nondeterministic seed based on the address of arena reduces
-		 * the likelihood of lockstep non-uniform cache index
-		 * utilization among identical concurrent processes, but at the
-		 * cost of test repeatability.  For debug builds, instead use a
-		 * deterministic seed.
-		 */
-		atomic_store_zu(&arena->offset_state, config_debug ? ind :
-		    (size_t)(uintptr_t)arena, ATOMIC_RELAXED);
-	}
-
 	atomic_store_zu(&arena->extent_sn_next, 0, ATOMIC_RELAXED);
 
 	atomic_store_u(&arena->dss_prec, (unsigned)extent_dss_prec_get(),
diff --git a/src/extent.c b/src/extent.c
index 4bb358d4..50a81055 100644
--- a/src/extent.c
+++ b/src/extent.c
@@ -187,8 +187,8 @@ extent_addr_randomize(tsdn_t *tsdn, arena_t *arena, extent_t *extent,
 			r = (size_t)prng_lg_range_u64(
 			    tsd_offset_statep_get(tsd), lg_range);
 		} else {
-			r = prng_lg_range_zu(&arena->offset_state, lg_range,
-			    true);
+			uint64_t stack_value = (uint64_t)(uintptr_t)&r;
+			r = (size_t)prng_lg_range_u64(&stack_value, lg_range);
 		}
 		uintptr_t random_offset = ((uintptr_t)r) << (LG_PAGE -
 		    lg_range);