--- libmalloc/libmalloc-283/tests/magazine_rack.c
+++ libmalloc/libmalloc-409.81.2/tests/magazine_rack.c
@@ -8,6 +8,9 @@
 
 #include <darwintest.h>
 #include "magazine_testing.h"
+
+// Stubs
+malloc_zero_policy_t malloc_zero_policy = MALLOC_ZERO_POLICY_DEFAULT;
 
 T_GLOBAL_META(T_META_RUN_CONCURRENTLY(true));
 
@@ -33,3 +36,90 @@
 	rack_destroy(&rack);
 	T_ASSERT_NULL(rack.magazines, "magazine deinit");
 }
+
+void *
+pressure_thread(void *arg)
+{
+	T_LOG("pressure thread started\n");
+	while (1) {
+		malloc_zone_pressure_relief(0, 0);
+	}
+}
+
+void *
+thread(void *arg)
+{
+	uintptr_t sz = (uintptr_t)arg;
+	T_LOG("thread started (allocation size: %lu bytes)\n", sz);
+	void *temp = malloc(sz);
+
+	uint64_t c = 100;
+	while (c-- > 0) {
+		uint32_t num = arc4random_uniform(100000);
+		void **allocs = malloc(sizeof(void *) * num);
+
+		for (int i=0; i<num; i++) {
+			allocs[i] = malloc(sz);
+		}
+		for (int i=0; i<num; i++) {
+			free(allocs[num - 1 - i]);
+		}
+		free((void *)allocs);
+	}
+	free(temp);
+	return NULL;
+}
+
+T_DECL(rack_tiny_region_remove, "exercise region deallocation race (rdar://66713029)")
+{
+	pthread_t p1;
+	pthread_create(&p1, NULL, pressure_thread, NULL);
+
+	const int threads = 8;
+	pthread_t p[threads];
+
+	for (int i=0; i<threads; i++) {
+		pthread_create(&p[i], NULL, thread, (void *)128);
+	}
+	for (int i=0; i<threads; i++) {
+		pthread_join(p[i], NULL);
+	}
+	T_PASS("finished without crashing");
+}
+
+T_DECL(rack_small_region_remove, "exercise region deallocation race (rdar://66713029)")
+{
+	pthread_t p1;
+	pthread_create(&p1, NULL, pressure_thread, NULL);
+
+	const int threads = 8;
+	pthread_t p[threads];
+
+	for (int i=0; i<threads; i++) {
+		pthread_create(&p[i], NULL, thread, (void *)1024);
+	}
+	for (int i=0; i<threads; i++) {
+		pthread_join(p[i], NULL);
+	}
+	T_PASS("finished without crashing");
+}
+
+T_DECL(rack_medium_region_remove, "exercise region deallocation race (rdar://66713029)",
+	   T_META_ENVVAR("MallocMediumZone=1"),
+	   T_META_ENVVAR("MallocMediumActivationThreshold=1"),
+	   T_META_ENABLED(CONFIG_MEDIUM_ALLOCATOR))
+{
+	pthread_t p1;
+	pthread_create(&p1, NULL, pressure_thread, NULL);
+
+	const int threads = 8;
+	pthread_t p[threads];
+
+	for (int i=0; i<threads; i++) {
+		pthread_create(&p[i], NULL, thread, (void *)65536);
+	}
+	for (int i=0; i<threads; i++) {
+		pthread_join(p[i], NULL);
+	}
+	T_PASS("finished without crashing");
+}