diff --git a/include/jemalloc/internal/arena_externs.h b/include/jemalloc/internal/arena_externs.h
index d0af91bf..d6556dae 100644
--- a/include/jemalloc/internal/arena_externs.h
+++ b/include/jemalloc/internal/arena_externs.h
@@ -60,8 +60,8 @@ bool	arena_ralloc_no_move(tsdn_t *tsdn, extent_t *extent, void *ptr,
     size_t oldsize, size_t size, size_t extra, bool zero);
 void	*arena_ralloc(tsdn_t *tsdn, arena_t *arena, extent_t *extent, void *ptr,
     size_t oldsize, size_t size, size_t alignment, bool zero, tcache_t *tcache);
-dss_prec_t	arena_dss_prec_get(tsdn_t *tsdn, arena_t *arena);
-bool	arena_dss_prec_set(tsdn_t *tsdn, arena_t *arena, dss_prec_t dss_prec);
+dss_prec_t	arena_dss_prec_get(arena_t *arena);
+bool	arena_dss_prec_set(arena_t *arena, dss_prec_t dss_prec);
 ssize_t	arena_decay_time_default_get(void);
 bool	arena_decay_time_default_set(ssize_t decay_time);
 void	arena_basic_stats_merge(tsdn_t *tsdn, arena_t *arena,
diff --git a/include/jemalloc/internal/arena_structs_b.h b/include/jemalloc/internal/arena_structs_b.h
index 8629446d..dde26894 100644
--- a/include/jemalloc/internal/arena_structs_b.h
+++ b/include/jemalloc/internal/arena_structs_b.h
@@ -156,7 +156,7 @@ struct arena_s {
 	 */
 	size_t			extent_sn_next;
 
-	/* Synchronization: lock. */
+	/* Synchronization: atomic. */
 	dss_prec_t		dss_prec;
 
 	/*
diff --git a/src/arena.c b/src/arena.c
index 5905306c..345c57df 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -1404,23 +1404,16 @@ arena_ralloc(tsdn_t *tsdn, arena_t *arena, extent_t *extent, void *ptr,
 }
 
 dss_prec_t
-arena_dss_prec_get(tsdn_t *tsdn, arena_t *arena) {
-	dss_prec_t ret;
-
-	malloc_mutex_lock(tsdn, &arena->lock);
-	ret = arena->dss_prec;
-	malloc_mutex_unlock(tsdn, &arena->lock);
-	return ret;
+arena_dss_prec_get(arena_t *arena) {
+	return (dss_prec_t)atomic_read_u((unsigned *)&arena->dss_prec);
 }
 
 bool
-arena_dss_prec_set(tsdn_t *tsdn, arena_t *arena, dss_prec_t dss_prec) {
+arena_dss_prec_set(arena_t *arena, dss_prec_t dss_prec) {
 	if (!have_dss) {
 		return (dss_prec != dss_prec_disabled);
 	}
-	malloc_mutex_lock(tsdn, &arena->lock);
-	arena->dss_prec = dss_prec;
-	malloc_mutex_unlock(tsdn, &arena->lock);
+	atomic_write_u((unsigned *)&arena->dss_prec, dss_prec);
 	return false;
 }
 
@@ -1442,7 +1435,7 @@ static void
 arena_basic_stats_merge_locked(arena_t *arena, unsigned *nthreads,
     const char **dss, ssize_t *decay_time, size_t *nactive, size_t *ndirty) {
 	*nthreads += arena_nthreads_get(arena, false);
-	*dss = dss_prec_names[arena->dss_prec];
+	*dss = dss_prec_names[arena_dss_prec_get(arena)];
 	*decay_time = arena->decay.time;
 	*nactive += atomic_read_zu(&arena->nactive);
 	*ndirty += extents_npages_get(&arena->extents_cached);
diff --git a/src/ctl.c b/src/ctl.c
index 403bc30c..0bf4258e 100644
--- a/src/ctl.c
+++ b/src/ctl.c
@@ -1767,11 +1767,11 @@ arena_i_dss_ctl(tsd_t *tsd, const size_t *mib, size_t miblen, void *oldp,
 	} else {
 		arena_t *arena = arena_get(tsd_tsdn(tsd), arena_ind, false);
 		if (arena == NULL || (dss_prec != dss_prec_limit &&
-		    arena_dss_prec_set(tsd_tsdn(tsd), arena, dss_prec))) {
+		    arena_dss_prec_set(arena, dss_prec))) {
 			ret = EFAULT;
 			goto label_return;
 		}
-		dss_prec_old = arena_dss_prec_get(tsd_tsdn(tsd), arena);
+		dss_prec_old = arena_dss_prec_get(arena);
 	}
 
 	dss = dss_prec_names[dss_prec_old];