Prefer aligned_alloc over posix_memalign

aligned_alloc is more cleaner and portable.

Author: AZero13

src/allocator.c

@@ -531,43 +531,42 @@ _dispatch_alloc_maybe_madvise_page(dispatch_continuation_t c)
 		return;
 	}
 	// Are all the continuations in this page unallocated?
-	volatile bitmap_t *page_bitmaps;
+	bitmap_t *page_bitmaps;
 	get_maps_and_indices_for_continuation((dispatch_continuation_t)page, NULL,
-			NULL, (bitmap_t **)&page_bitmaps, NULL);
+			NULL, &page_bitmaps, NULL);
 	unsigned int i;
 	for (i = 0; i < BITMAPS_PER_PAGE; i++) {
-		if (page_bitmaps[i] != 0) {
+		if (os_atomic_load(&page_bitmaps[i], relaxed) != 0) {
 			return;
 		}
 	}
 	// They are all unallocated, so we could madvise the page. Try to
 	// take ownership of them all.
-	int last_locked = 0;
-	do {
-		if (!os_atomic_cmpxchg(&page_bitmaps[last_locked], BITMAP_C(0),
+	for (i = 0; i < BITMAPS_PER_PAGE; i++) {
+		if (!os_atomic_cmpxchg(&page_bitmaps[i], BITMAP_C(0),
 				BITMAP_ALL_ONES, relaxed)) {
 			// We didn't get one; since there is a cont allocated in
 			// the page, we can't madvise. Give up and unlock all.
-			goto unlock;
+			break;
 		}
-	} while (++last_locked < (signed)BITMAPS_PER_PAGE);
+	}
+
+	if (i >= BITMAPS_PER_PAGE) {
 #if DISPATCH_DEBUG
-	//fprintf(stderr, "%s: madvised page %p for cont %p (next = %p), "
-	//		"[%u+1]=%u bitmaps at %p\n", __func__, page, c, c->do_next,
-	//		last_locked-1, BITMAPS_PER_PAGE, &page_bitmaps[0]);
-	// Scribble to expose use-after-free bugs
-	// madvise (syscall) flushes these stores
-	memset(page, DISPATCH_ALLOCATOR_SCRIBBLE, DISPATCH_ALLOCATOR_PAGE_SIZE);
+		// fprintf(stderr, "%s: madvised page %p for cont %p (next = %p), "
+		//		"[%u+1]=%u bitmaps at %p\n", __func__, page, c, c->do_next,
+		//		last_locked-1, BITMAPS_PER_PAGE, &page_bitmaps[0]);
+		//  Scribble to expose use-after-free bugs
+		//  madvise (syscall) flushes these stores
+		memset(page, DISPATCH_ALLOCATOR_SCRIBBLE, DISPATCH_ALLOCATOR_PAGE_SIZE);
 #endif
-	(void)dispatch_assume_zero(madvise(page, DISPATCH_ALLOCATOR_PAGE_SIZE,
-			MADV_FREE));
-
-unlock:
-	while (last_locked > 1) {
-		page_bitmaps[--last_locked] = BITMAP_C(0);
+		// madvise the page
+		(void)dispatch_assume_zero(madvise(page, DISPATCH_ALLOCATOR_PAGE_SIZE,
+				MADV_FREE));
 	}
-	if (last_locked) {
-		os_atomic_store(&page_bitmaps[0], BITMAP_C(0), relaxed);
+
+	while (i) {
+		os_atomic_store(&page_bitmaps[--i], BITMAP_C(0), relaxed);
 	}
 	return;
 }

src/io.c

@@ -2374,10 +2374,7 @@ _dispatch_operation_perform(dispatch_operation_t op)
 			}
 			op->buf = _aligned_malloc(op->buf_siz, siInfo.dwPageSize);
 #else
-			err = posix_memalign(&op->buf, (size_t)PAGE_SIZE, op->buf_siz);
-			if (err != 0) {
-				goto error;
-			}
+			op->buf = aligned_alloc((size_t)PAGE_SIZE, op->buf_siz)
 #endif
 			_dispatch_op_debug("buffer allocated", op);
 		} else if (op->direction == DOP_DIR_WRITE) {

tests/dispatch_io.c

@@ -398,7 +398,7 @@ test_async_read(char *path, size_t size, int option, dispatch_queue_t queue,
 				buffer = _aligned_malloc(size, si.dwPageSize);
 #else
 				size_t pagesize = (size_t)sysconf(_SC_PAGESIZE);
-				posix_memalign((void **)&buffer, pagesize, size);
+				buffer = aligned_alloc(pagesize, size);
 #endif
 				ssize_t r = dispatch_test_fd_read(fd, buffer, size);
 				if (r == -1) {

tests/dispatch_read2.c

@@ -91,7 +91,7 @@ dispatch_read2(dispatch_fd_t fd,
 		buffer = _aligned_malloc(bufsiz, pagesize);
 #else
 		size_t pagesize = (size_t)sysconf(_SC_PAGESIZE);
-		posix_memalign((void **)&buffer, pagesize, bufsiz);
+		buffer = aligned_alloc(pagesize, bufsiz);
 #endif
 		ssize_t actual = dispatch_test_fd_read(fd, buffer, bufsiz);
 		if (actual == -1) {