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--- libmalloc/libmalloc-317.100.9/src/magazine_small.c
+++ libmalloc/libmalloc-283.100.6/src/magazine_small.c
@@ -72,13 +72,13 @@
 {
 #if CONFIG_SMALL_USES_HYPER_SHIFT
 	if (os_likely(_os_cpu_number_override == -1)) {
-		return _malloc_cpu_number() >> hyper_shift;
+		return _os_cpu_number() >> hyper_shift;
 	} else {
 		return _os_cpu_number_override >> hyper_shift;
 	}
 #else // CONFIG_SMALL_USES_HYPER_SHIFT
 	if (os_likely(_os_cpu_number_override == -1)) {
-		return _malloc_cpu_number();
+		return _os_cpu_number();
 	} else {
 		return _os_cpu_number_override;
 	}
@@ -994,30 +994,18 @@
 	for (mag_index = 0; mag_index < rack->num_magazines; mag_index++) {
 		size_t index;
 		for (index = 0; index < rack->region_generation->num_regions_allocated; ++index) {
-			rack_region_lock(rack);
+			SZONE_LOCK(SMALL_SZONE_FROM_RACK(rack));
 
 			region_t small = rack->region_generation->hashed_regions[index];
 			if (!small || small == HASHRING_REGION_DEALLOCATED) {
-				rack_region_unlock(rack);
+				SZONE_UNLOCK(SMALL_SZONE_FROM_RACK(rack));
 				continue;
 			}
 
-			region_trailer_t *trailer = REGION_TRAILER_FOR_SMALL_REGION(small);
-			// Make sure that the owning magazine doesn't try and take this out
-			// from under our feet.
-			trailer->dispose_flags |= RACK_DISPOSE_DELAY;
-			rack_region_unlock(rack);
-
 			magazine_t *mag_ptr = mag_lock_zine_for_region_trailer(rack->magazines,
-					trailer, MAGAZINE_INDEX_FOR_SMALL_REGION(small));
-
-			// If acquiring the region lock was enough to prevent the owning
-			// magazine from deallocating the region, free it now so we don't
-			// do wasted work.
-			if (rack_region_maybe_dispose(rack, small, SMALL_REGION_SIZE, trailer)) {
-				SZONE_MAGAZINE_PTR_UNLOCK(mag_ptr);
-				continue;
-			}
+					REGION_TRAILER_FOR_SMALL_REGION(small),
+					MAGAZINE_INDEX_FOR_SMALL_REGION(small));
+			SZONE_UNLOCK(SMALL_SZONE_FROM_RACK(rack));
 
 			/* Ordering is important here, the magazine of a region may potentially change
 			 * during mag_lock_zine_for_region_trailer, so src_mag_index must be taken
@@ -1155,18 +1143,31 @@
 	int objects_in_use = small_free_detach_region(rack, depot_ptr, sparse_region);
 
 	if (0 == objects_in_use) {
-		if (!rack_region_remove(rack, sparse_region, node)) {
+		// Invalidate the hash table entry for this region with HASHRING_REGION_DEALLOCATED.
+		// Using HASHRING_REGION_DEALLOCATED preserves the collision chain, using HASHRING_OPEN_ENTRY (0) would not.
+		rgnhdl_t pSlot = hash_lookup_region_no_lock(rack->region_generation->hashed_regions,
+													rack->region_generation->num_regions_allocated,
+													rack->region_generation->num_regions_allocated_shift,
+													sparse_region);
+		if (NULL == pSlot) {
+			malloc_zone_error(rack->debug_flags, true, "small_free_try_depot_unmap_no_lock hash lookup failed: %p\n", sparse_region);
 			return NULL;
 		}
+		*pSlot = HASHRING_REGION_DEALLOCATED;
 		depot_ptr->num_bytes_in_magazine -= SMALL_HEAP_SIZE;
+		// Atomically increment num_regions_dealloc
+#ifdef __LP64___
+		OSAtomicIncrement64(&rack->num_regions_dealloc);
+#else
+		OSAtomicIncrement32((int32_t *)&rack->num_regions_dealloc);
+#endif
 
 		// Caller will transfer ownership of the region back to the OS with no locks held
 		MAGMALLOC_DEALLOCREGION(SMALL_SZONE_FROM_RACK(rack), (void *)sparse_region, (int)SMALL_REGION_SIZE); // DTrace USDT Probe
 		return sparse_region;
 
 	} else {
-		malloc_zone_error(rack->debug_flags, true,
-				"small_free_try_depot_unmap_no_lock objects_in_use not zero: %d\n", objects_in_use);
+		malloc_zone_error(rack->debug_flags, true, "small_free_try_depot_unmap_no_lock objects_in_use not zero: %d\n", objects_in_use);
 		return NULL;
 	}
 }
@@ -1231,13 +1232,10 @@
 	MAGMALLOC_RECIRCREGION(SMALL_SZONE_FROM_RACK(rack), (int)mag_index, (void *)sparse_region, SMALL_REGION_SIZE,
 						   (int)BYTES_USED_FOR_SMALL_REGION(sparse_region)); // DTrace USDT Probe
 
-#if CONFIG_AGGRESSIVE_MADVISE
-	if (!aggressive_madvise_enabled)
-#endif
-	{
-		// Mark free'd dirty pages with MADV_FREE to reduce memory pressure
-		small_free_scan_madvise_free(rack, depot_ptr, sparse_region);
-	}
+#if !CONFIG_AGGRESSIVE_MADVISE
+	// Mark free'd dirty pages with MADV_FREE to reduce memory pressure
+	small_free_scan_madvise_free(rack, depot_ptr, sparse_region);
+#endif
 
 	// If the region is entirely empty vm_deallocate() it outside the depot lock
 	region_t r_dealloc = small_free_try_depot_unmap_no_lock(rack, depot_ptr, node);
@@ -1284,14 +1282,11 @@
 			return small_free_do_recirc_to_depot(rack, small_mag_ptr, mag_index);
 		}
 	} else {
-#if CONFIG_AGGRESSIVE_MADVISE
-		if (!aggressive_madvise_enabled)
-#endif
-		{
-			// We are free'ing into the depot, so madvise as we do so unless we were madvising every incoming
-			// allocation anyway.
-			small_madvise_free_range_no_lock(rack, small_mag_ptr, region, freee, msize, headptr, headsize);
-		}
+#if !CONFIG_AGGRESSIVE_MADVISE
+		// We are free'ing into the depot, so madvise as we do so unless we were madvising every incoming
+		// allocation anyway.
+		small_madvise_free_range_no_lock(rack, small_mag_ptr, region, freee, msize, headptr, headsize);
+#endif
 
 		if (0 < bytes_used || 0 < node->pinned_to_depot) {
 			/* Depot'd region is still live. Leave it in place on the Depot's recirculation list
@@ -1386,9 +1381,7 @@
 	trailer->bytes_used = (unsigned int)bytes_used;
 
 #if CONFIG_AGGRESSIVE_MADVISE
-	if (aggressive_madvise_enabled) {
-		small_madvise_free_range_no_lock(rack, small_mag_ptr, region, freee, msize, original_ptr, original_size);
-	}
+	small_madvise_free_range_no_lock(rack, small_mag_ptr, region, freee, msize, original_ptr, original_size);
 #endif
 
 	// Caller must do SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr) if this function
@@ -2211,6 +2204,9 @@
 static MALLOC_NOINLINE void
 free_small_botch(rack_t *rack, void *ptr)
 {
+	mag_index_t mag_index = MAGAZINE_INDEX_FOR_SMALL_REGION(SMALL_REGION_FOR_PTR(ptr));
+	magazine_t *small_mag_ptr = &(rack->magazines[mag_index]);
+	SZONE_MAGAZINE_PTR_UNLOCK(small_mag_ptr);
 	malloc_zone_error(rack->debug_flags, true, "double free for ptr %p\n", ptr);
 }
 
@@ -2243,7 +2239,6 @@
 
 		/* check that we don't already have this pointer in the cache */
 		if (ptr == ptr2) {
-			SZONE_MAGAZINE_PTR_UNLOCK(small_mag_ptr);
 			free_small_botch(rack, ptr);
 			return;
 		}