1 files changed, 78 insertions, 16 deletions

diff --git a/cpp/src/IceUtil/Shared.cpp b/cpp/src/IceUtil/Shared.cpp
index f18b9385798..1121ab3c823 100644
--- a/cpp/src/IceUtil/Shared.cpp
+++ b/cpp/src/IceUtil/Shared.cpp
@@ -10,7 +10,79 @@
 #include <IceUtil/Shared.h>
 
 using namespace IceUtil;
-using namespace IceUtilInternal;
+
+#ifdef ICE_HAS_ATOMIC_FUNCTIONS
+
+namespace IceUtilInternal
+{
+
+//
+// Linux only. Unfortunately, asm/atomic.h builds non-SMP safe code
+// with non-SMP kernels. This means that executables compiled with a
+// non-SMP kernel would fail randomly due to concurrency errors with
+// reference counting on SMP hosts. Therefore the relevent pieces of
+// atomic.h are more-or-less duplicated.
+//
+
+/*
+ * atomicInc - increment ice_atomic variable
+ * @v: pointer of type AtomicCounter
+ * 
+ * Atomically increments @v by 1. Note that the guaranteed useful
+ * range of an AtomicCounter is only 24 bits.
+ *
+ * Inlined because this operation is performance critical.
+ */
+static inline void atomicInc(volatile int* counter)
+{
+    __asm__ __volatile__(
+	"lock ; incl %0"
+	:"=m" (*counter)
+	:"m" (*counter));
+}
+
+/**
+ * atomicDecAndTest - decrement and test
+ * @v: pointer of type AtomicCounter
+ * 
+ * Atomically decrements @v by 1 and returns true if the result is 0,
+ * or false for all other cases. Note that the guaranteed useful
+ * range of an AtomicCounter is only 24 bits.
+ *
+ * Inlined because this operation is performance critical.
+ */
+static inline int atomicDecAndTest(volatile int* counter)
+{
+    unsigned char c;
+    __asm__ __volatile__(
+	"lock ; decl %0; sete %1"
+	:"=m" (*counter), "=qm" (c)
+	:"m" (*counter) : "memory");
+    return c != 0;
+}
+
+/**
+ * atomicExchangeAdd - same as InterlockedExchangeAdd. This
+ * didn't come from atomic.h (the code was derived from similar code
+ * in /usr/include/asm/rwsem.h)
+ *
+ * Inlined because this operation is performance critical.
+ */
+static inline int atomicExchangeAdd(volatile int* counter, int i)
+{
+    int tmp = i;
+    __asm__ __volatile__(
+	"lock ; xadd %0,(%2)"
+	:"+r"(tmp), "=m"(*counter)
+	:"r"(counter), "m"(*counter)
+	: "memory");
+    return tmp + i;
+}
+
+}
+
+#endif
+
 
 IceUtil::SimpleShared::SimpleShared() :
     _ref(0),
@@ -25,25 +97,15 @@ IceUtil::SimpleShared::SimpleShared(const SimpleShared&) :
 }
 
 IceUtil::Shared::Shared() :
-#ifndef ICE_HAS_ATOMIC_FUNCTIONS
     _ref(0),
-#endif
     _noDelete(false)
 {
-#ifdef ICE_HAS_ATOMIC_FUNCTIONS
-    _ref.atomicSet(0);
-#endif
 }
 
 IceUtil::Shared::Shared(const Shared&) :
-#ifndef ICE_HAS_ATOMIC_FUNCTIONS
     _ref(0),
-#endif
     _noDelete(false)
 {
-#ifdef ICE_HAS_ATOMIC_FUNCTIONS
-    _ref.atomicSet(0);
-#endif
 }
 
 void 
@@ -53,8 +115,8 @@ IceUtil::Shared::__incRef()
     assert(InterlockedExchangeAdd(&_ref, 0) >= 0);
     InterlockedIncrement(&_ref);
 #elif defined(ICE_HAS_ATOMIC_FUNCTIONS)
-    assert(_ref.atomicExchangeAdd(&_ref) >= 0);
-    _ref.atomicInc();
+    assert(IceUtilInternal::atomicExchangeAdd(&_ref, 0) >= 0);
+    IceUtilInternal::atomicInc(&_ref);
 #else
     _mutex.lock();
     assert(_ref >= 0);
@@ -74,8 +136,8 @@ IceUtil::Shared::__decRef()
         delete this;
     }
 #elif defined(ICE_HAS_ATOMIC_FUNCTIONS)
-    assert(_ref.atomicExchangeAdd(0) > 0);
-    if(_ref.atomicDecAndTest() && !_noDelete)
+    assert(IceUtilInternal::atomicExchangeAdd(&_ref, 0) > 0);
+    if(IceUtilInternal::atomicDecAndTest(&_ref) && !_noDelete)
     {
         _noDelete = true;
         delete this;
@@ -103,7 +165,7 @@ IceUtil::Shared::__getRef() const
 #if defined(_WIN32)
     return InterlockedExchangeAdd(const_cast<LONG*>(&_ref), 0);
 #elif defined(ICE_HAS_ATOMIC_FUNCTIONS)
-    return const_cast<IceUtilInternal::AtomicCounter*>(&_ref)->atomicExchangeAdd(0);
+    return IceUtilInternal::atomicExchangeAdd(const_cast<volatile int*>(&_ref), 0);
 #else
     _mutex.lock();
     int ref = _ref;