Use semaphores instead of condition variables

src/net.cpp

@@ -35,7 +35,7 @@ void ThreadOpenAddedConnections2(void* parg);
 void ThreadMapPort2(void* parg);
 #endif
 void ThreadDNSAddressSeed2(void* parg);
-bool OpenNetworkConnection(const CAddress& addrConnect);
+bool OpenNetworkConnection(const CAddress& addrConnect, bool fUseGrant = true);
 
 
 
@@ -64,10 +64,7 @@ map<CInv, int64> mapAlreadyAskedFor;
 set<CNetAddr> setservAddNodeAddresses;
 CCriticalSection cs_setservAddNodeAddresses;
 
-static CWaitableCriticalSection csOutbound;
-static int nOutbound = 0;
-static CConditionVariable condOutbound;
-
+static CSemaphore *semOutbound = NULL;
 
 unsigned short GetListenPort()
 {
@@ -368,10 +365,6 @@ CNode* ConnectNode(CAddress addrConnect, int64 nTimeout)
             LOCK(cs_vNodes);
             vNodes.push_back(pnode);
         }
-        {
-            WAITABLE_LOCK(csOutbound);
-            nOutbound++;
-        }
 
         pnode->nTimeConnected = GetTime();
         return pnode;
@@ -517,14 +510,9 @@ void ThreadSocketHandler2(void* parg)
                     // remove from vNodes
                     vNodes.erase(remove(vNodes.begin(), vNodes.end(), pnode), vNodes.end());
 
-                    if (!pnode->fInbound)
-                        {
-                            WAITABLE_LOCK(csOutbound);
-                            nOutbound--;
-
-                            // Connection slot(s) were removed, notify connection creator(s)
-                            NOTIFY(condOutbound);
-                        }
+                    if (pnode->fHasGrant)
+                        semOutbound->post();
+                    pnode->fHasGrant = false;
 
                     // close socket and cleanup
                     pnode->CloseSocketDisconnect();
@@ -1201,7 +1189,7 @@ void ThreadOpenConnections2(void* parg)
             {
                 CAddress addr(CService(strAddr, GetDefaultPort(), fAllowDNS));
                 if (addr.IsValid())
-                    OpenNetworkConnection(addr);
+                    OpenNetworkConnection(addr, false);
                 for (int i = 0; i < 10 && i < nLoop; i++)
                 {
                     Sleep(500);
@@ -1222,13 +1210,9 @@ void ThreadOpenConnections2(void* parg)
         if (fShutdown)
             return;
 
-        // Limit outbound connections
-        int nMaxOutbound = min(MAX_OUTBOUND_CONNECTIONS, (int)GetArg("-maxconnections", 125));
+
         vnThreadsRunning[THREAD_OPENCONNECTIONS]--;
-        {
-            WAITABLE_LOCK(csOutbound);
-            WAIT(condOutbound, fShutdown || nOutbound < nMaxOutbound);
-        }
+        semOutbound->wait();
         vnThreadsRunning[THREAD_OPENCONNECTIONS]++;
         if (fShutdown)
             return;
@@ -1261,11 +1245,15 @@ void ThreadOpenConnections2(void* parg)
 
         // Only connect to one address per a.b.?.? range.
         // Do this here so we don't have to critsect vNodes inside mapAddresses critsect.
+        int nOutbound = 0;
         set<vector<unsigned char> > setConnected;
         {
             LOCK(cs_vNodes);
-            BOOST_FOREACH(CNode* pnode, vNodes)
+            BOOST_FOREACH(CNode* pnode, vNodes) {
                 setConnected.insert(pnode->addr.GetGroup());
+                if (!pnode->fInbound)
+                    nOutbound++;
+            }
         }
 
         int64 nANow = GetAdjustedTime();
@@ -1296,6 +1284,8 @@ void ThreadOpenConnections2(void* parg)
 
         if (addrConnect.IsValid())
             OpenNetworkConnection(addrConnect);
+        else
+            semOutbound->post();
     }
 }
 
@@ -1358,6 +1348,7 @@ void ThreadOpenAddedConnections2(void* parg)
         }
         BOOST_FOREACH(vector<CService>& vserv, vservConnectAddresses)
         {
+            semOutbound->wait();
             OpenNetworkConnection(CAddress(*(vserv.begin())));
             Sleep(500);
             if (fShutdown)
@@ -1373,7 +1364,14 @@ void ThreadOpenAddedConnections2(void* parg)
     }
 }
 
-bool OpenNetworkConnection(const CAddress& addrConnect)
+bool static ReleaseGrant(bool fUseGrant) {
+    if (fUseGrant)
+        semOutbound->post();
+    return false;
+}
+
+// only call this function when semOutbound has been waited for
+bool OpenNetworkConnection(const CAddress& addrConnect, bool fUseGrant)
 {
     //
     // Initiate outbound network connection
@@ -1382,7 +1380,7 @@ bool OpenNetworkConnection(const CAddress& addrConnect)
         return false;
     if ((CNetAddr)addrConnect == (CNetAddr)addrLocalHost || !addrConnect.IsIPv4() ||
         FindNode((CNetAddr)addrConnect) || CNode::IsBanned(addrConnect))
-        return false;
+        return ReleaseGrant(fUseGrant);
 
     vnThreadsRunning[THREAD_OPENCONNECTIONS]--;
     CNode* pnode = ConnectNode(addrConnect);
@@ -1390,7 +1388,13 @@ bool OpenNetworkConnection(const CAddress& addrConnect)
     if (fShutdown)
         return false;
     if (!pnode)
-        return false;
+        return ReleaseGrant(fUseGrant);
+    if (pnode->fHasGrant) {
+        // node already has connection grant, release the one that was passed to us
+        ReleaseGrant(fUseGrant);
+    } else {
+        pnode->fHasGrant = fUseGrant;
+    }
     pnode->fNetworkNode = true;
 
     return true;
@@ -1567,6 +1571,12 @@ bool BindListenPort(string& strError)
 
 void StartNode(void* parg)
 {
+    if (semOutbound == NULL) {
+        // initialize semaphore
+        int nMaxOutbound = min(MAX_OUTBOUND_CONNECTIONS, (int)GetArg("-maxconnections", 125));
+        semOutbound = new CSemaphore(nMaxOutbound);
+    }
+
 #ifdef USE_UPNP
 #if USE_UPNP
     fUseUPnP = GetBoolArg("-upnp", true);
@@ -1693,7 +1703,8 @@ bool StopNode()
     fShutdown = true;
     nTransactionsUpdated++;
     int64 nStart = GetTime();
-    NOTIFY_ALL(condOutbound);
+    for (int i=0; i<MAX_OUTBOUND_CONNECTIONS; i++)
+         semOutbound->post();
     do
     {
         int nThreadsRunning = 0;

src/net.h

@@ -127,6 +127,7 @@ public:
     bool fNetworkNode;
     bool fSuccessfullyConnected;
     bool fDisconnect;
+    bool fHasGrant; // whether to call semOutbound.post() at disconnect
 protected:
     int nRefCount;
 
@@ -171,6 +172,7 @@ public:
         nVersion = 0;
         strSubVer = "";
         fClient = false; // set by version message
+        fHasGrant = false;
         fInbound = fInboundIn;
         fNetworkNode = false;
         fSuccessfullyConnected = false;

src/util.h

@@ -23,7 +23,7 @@ typedef int pid_t; /* define for windows compatiblity */
 #include <boost/filesystem/path.hpp>
 #include <boost/interprocess/sync/interprocess_recursive_mutex.hpp>
 #include <boost/interprocess/sync/scoped_lock.hpp>
-#include <boost/interprocess/sync/interprocess_condition.hpp>
+#include <boost/interprocess/sync/interprocess_semaphore.hpp>
 #include <boost/interprocess/sync/lock_options.hpp>
 #include <boost/date_time/gregorian/gregorian_types.hpp>
 #include <boost/date_time/posix_time/posix_time_types.hpp>
@@ -270,24 +270,10 @@ public:
 };
 
 typedef CMutexLock<CCriticalSection> CCriticalBlock;
-typedef CMutexLock<CWaitableCriticalSection> CWaitableCriticalBlock;
-typedef boost::interprocess::interprocess_condition CConditionVariable;
-
-/** Wait for a given condition inside a WAITABLE_CRITICAL_BLOCK */
-#define WAIT(name,condition) \
-   do { while(!(condition)) { (name).wait(waitablecriticalblock.GetLock()); } } while(0)
-
-/** Notify waiting threads that a condition may hold now */
-#define NOTIFY(name) \
-   do { (name).notify_one(); } while(0)
-
-#define NOTIFY_ALL(name) \
-   do { (name).notify_all(); } while(0)
 
 #define LOCK(cs) CCriticalBlock criticalblock(cs, #cs, __FILE__, __LINE__)
 #define LOCK2(cs1,cs2) CCriticalBlock criticalblock1(cs1, #cs1, __FILE__, __LINE__),criticalblock2(cs2, #cs2, __FILE__, __LINE__)
 #define TRY_LOCK(cs,name) CCriticalBlock name(cs, #cs, __FILE__, __LINE__, true)
-#define WAITABLE_LOCK(cs) CWaitableCriticalBlock waitablecriticalblock(cs, #cs, __FILE__, __LINE__)
 
 #define ENTER_CRITICAL_SECTION(cs) \
     { \
@@ -301,6 +287,7 @@ typedef boost::interprocess::interprocess_condition CConditionVariable;
         LeaveCritical(); \
     }
 
+typedef boost::interprocess::interprocess_semaphore CSemaphore;
 
 inline std::string i64tostr(int64 n)
 {