From dc7e61e60fb6957717a978131c3dc2dca58cf44c Mon Sep 17 00:00:00 2001
From: midipix <writeonce@midipix.org>
Date: Thu, 9 Aug 2018 04:14:31 -0400
Subject: __ntapi_blt_possess(): use an inlined cmpxchg loop.

---
 src/blitter/ntapi_blt_block.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/blitter/ntapi_blt_block.c b/src/blitter/ntapi_blt_block.c
index 12dc2f7..803e723 100644
--- a/src/blitter/ntapi_blt_block.c
+++ b/src/blitter/ntapi_blt_block.c
@@ -135,14 +135,21 @@ int32_t __fastcall __ntapi_blt_possess(
 	size_t		byte;
 	uintptr_t 	test;
 	uintptr_t	mask;
+	uintptr_t	cmp;
+	uintptr_t	xchg;
 
 	bit  = *blkid % (8*sizeof(size_t));
 	byte = *blkid / (8*sizeof(size_t));
+	mask = (uintptr_t)1 << bit;
+
+	do {
+		cmp  = blitter->bitmap[byte];
+		xchg = cmp & ~mask;
 
-	mask = ((uintptr_t)1 << bit);
-	test  = at_locked_and(
-		(intptr_t *)&blitter->bitmap[byte],
-		~mask);
+		test = at_locked_cas(
+			(intptr_t *)&blitter->bitmap[byte],
+			cmp,xchg);
+	} while (test != cmp);
 
 	if (test & mask) {
 		at_locked_dec(&blitter->info.blocks_avail);
-- 
cgit v1.2.3