From 6d9e1270cadfb7850c8bc2e50168db8f0a82efef Mon Sep 17 00:00:00 2001
From: Joel Dice <git@seibutsu.mailsnare.net>
Date: Sun, 29 Nov 2009 09:08:07 -0700
Subject: [PATCH] fix race conditions in atomic operations

---
 src/heap.cpp    | 5 ++++-
 src/machine.cpp | 7 +++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/heap.cpp b/src/heap.cpp
index 740b9985af..5dcd75f7c2 100644
--- a/src/heap.cpp
+++ b/src/heap.cpp
@@ -76,7 +76,10 @@ markBitAtomic(uintptr_t* map, unsigned i)
 {
   uintptr_t* p = map + wordOf(i);
   uintptr_t v = static_cast<uintptr_t>(1) << bitOf(i);
-  while (not atomicCompareAndSwap(p, *p, *p | v)) { }
+  for (uintptr_t old = *p;
+       not atomicCompareAndSwap(p, old, old | v);
+       old = *p)
+  { }
 }
 #endif // USE_ATOMIC_OPERATIONS
 
diff --git a/src/machine.cpp b/src/machine.cpp
index 62c4649659..b9ae880225 100644
--- a/src/machine.cpp
+++ b/src/machine.cpp
@@ -24,9 +24,12 @@ const unsigned NoByte = 0xFFFF;
 
 #ifdef USE_ATOMIC_OPERATIONS
 void
-atomicIncrement(unsigned* p, int v)
+atomicIncrement(uint32_t* p, int v)
 {
-  while (not atomicCompareAndSwap32(p, *p, *p + v)) { }
+  for (uint32_t old = *p;
+       not atomicCompareAndSwap32(p, old, old + v);
+       old = *p)
+  { }
 }
 #endif