Make OID and MSGID increments atomic

db/jsobj.cpp

@@ -1430,7 +1430,7 @@ namespace mongo {
     }
     
     void OID::init() {
-        static unsigned inc = (unsigned) security.getNonce();
+        static WrappingInt inc = (unsigned) security.getNonce();
         unsigned t = (unsigned) time(0);
         char *T = (char *) &t;
         data[0] = T[3];
@@ -1440,9 +1440,8 @@ namespace mongo {
 
         (unsigned&) data[4] = _machine;
 
-        // TODO: use compiler intrinsic atomic increment instead of inc++
-        int old_inc = inc++;
-        T = (char *) &old_inc;
+        int new_inc = inc.atomicIncrement();
+        T = (char *) &new_inc;
         char * raw = (char*)&b;
         raw[0] = T[3];
         raw[1] = T[2];

util/goodies.h

@@ -19,6 +19,10 @@
 
 #pragma once
 
+#if defined(__MSCV__)
+#  include <windows.h>
+#endif
+
 namespace mongo {
 
 #if !defined(_WIN32) && !defined(NOEXECINFO)
@@ -112,14 +116,22 @@ namespace mongo {
             x = 0;
         }
         WrappingInt(unsigned z) : x(z) { }
-        unsigned x;
+        volatile unsigned x;
         operator unsigned() const {
             return x;
         }
-        WrappingInt& operator++() {
-            x++;
-            return *this;
+
+        WrappingInt atomicIncrement(){
+#if defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4)
+            return __sync_add_and_fetch(&x, 1);
+#elif defined(__MSCV__)
+            return InterlockedIncrement((long*)&x); //long is 32bits in Win64
+#else
+#  warning "OID and MSGID generation will not be thread safe"
+            return ++inc;
+#endif
         }
+
         static int diff(unsigned a, unsigned b) {
             return a-b;
         }

util/message.cpp

@@ -429,8 +429,7 @@ again:
     } msgstart;
     
     MSGID nextMessageId(){
-        MSGID msgid = NextMsgId;
-        ++NextMsgId;
+        MSGID msgid = NextMsgId.atomicIncrement();
         
         if ( usingClientIds ){
             msgid = msgid & 0xFFFF;