Added support for recursive write mutexes. Added read/write mutex upgrade.

3 files changed, 69 insertions, 35 deletions

diff --git a/cpp/src/IceUtil/.depend b/cpp/src/IceUtil/.depend
index 9690231d38c..8ce3722f926 100644
--- a/cpp/src/IceUtil/.depend
+++ b/cpp/src/IceUtil/.depend
@@ -2,7 +2,7 @@ Exception.o: Exception.cpp ../../include/IceUtil/Exception.h ../../include/IceUt
 Unicode.o: Unicode.cpp ../../include/IceUtil/Unicode.h ../../include/IceUtil/Config.h
 UUID.o: UUID.cpp ../../include/IceUtil/UUID.h ../../include/IceUtil/Config.h
 RecMutex.o: RecMutex.cpp ../../include/IceUtil/RecMutex.h ../../include/IceUtil/Config.h ../../include/IceUtil/Lock.h ../../include/IceUtil/Exception.h
-RWRecMutex.o: RWRecMutex.cpp ../../include/IceUtil/RWRecMutex.h ../../include/IceUtil/Mutex.h ../../include/IceUtil/Config.h ../../include/IceUtil/Exception.h ../../include/IceUtil/Lock.h ../../include/IceUtil/Cond.h
+RWRecMutex.o: RWRecMutex.cpp ../../include/IceUtil/RWRecMutex.h ../../include/IceUtil/Mutex.h ../../include/IceUtil/Config.h ../../include/IceUtil/Exception.h ../../include/IceUtil/Lock.h ../../include/IceUtil/Cond.h ../../include/IceUtil/Thread.h ../../include/IceUtil/Shared.h ../../include/IceUtil/Handle.h
 Cond.o: Cond.cpp ../../include/IceUtil/Cond.h ../../include/IceUtil/Config.h ../../include/IceUtil/Exception.h
 Thread.o: Thread.cpp ../../include/IceUtil/Thread.h ../../include/IceUtil/Shared.h ../../include/IceUtil/Config.h ../../include/IceUtil/Handle.h ../../include/IceUtil/Exception.h
 OutputUtil.o: OutputUtil.cpp ../../include/IceUtil/OutputUtil.h ../../include/IceUtil/Config.h
diff --git a/cpp/src/IceUtil/RWRecMutex.cpp b/cpp/src/IceUtil/RWRecMutex.cpp
index dd87a1ae245..b664381df5c 100644
--- a/cpp/src/IceUtil/RWRecMutex.cpp
+++ b/cpp/src/IceUtil/RWRecMutex.cpp
@@ -1,8 +1,8 @@
 // **********************************************************************
 //
 // Copyright (c) 2001
-// IONA Technologies, Inc.
-// Waltham, MA, USA
+// MutableRealms, Inc.
+// Huntsville, AL, USA
 //
 // All Rights Reserved
 //
@@ -61,6 +61,16 @@ IceUtil::RWRecMutex::writeLock() const
     Mutex::Lock lock(_mutex);
 
     //
+    // If the mutex is already write locked by this writer then
+    // decrement _count, and return.
+    //
+    if (_count < 0 && _writerControl == ThreadControl())
+    {
+	--_count;
+	return;
+    }
+
+    //
     // Wait for the lock to become available and increment the number
     // of waiting writers.
     //
@@ -91,6 +101,16 @@ IceUtil::RWRecMutex::tryWriteLock() const
     Mutex::Lock lock(_mutex);
 
     //
+    // If the mutex is already write locked by this writer then
+    // decrement _count, and return.
+    //
+    if (_count < 0 && _writerControl == ThreadControl())
+    {
+	--_count;
+	return;
+    }
+
+    //
     // If there are readers or other writers then the call would block.
     //
     if (_count != 0)
@@ -124,7 +144,15 @@ IceUtil::RWRecMutex::unlock() const
 	    //
 	    // Writer called unlock
 	    //
-	    _count = 0;
+	    ++_count;
+
+	    //
+	    // If the write lock wasn't totally released we're done.
+	    //
+	    if (_count != 0)
+	    {
+		return;
+	    }
 	}
 	else
 	{
@@ -163,3 +191,40 @@ IceUtil::RWRecMutex::unlock() const
 	_readers.broadcast();
     }
 }
+
+void
+IceUtil::RWRecMutex::upgrade() const
+{
+    Mutex::Lock lock(_mutex);
+
+    //
+    // Reader called unlock
+    //
+    assert(_count > 0);
+    --_count;
+
+    //
+    // Wait to acquire the write lock.
+    //
+    while (_count != 0)
+    {
+	_waitingWriters++;
+	try
+	{
+	    _writers.wait(lock);
+	}
+	catch(...)
+	{
+	    --_waitingWriters;
+	    throw;
+	}
+	_waitingWriters--;
+
+	
+    }
+
+    //
+    // Got the lock, indicate it's held by a writer.
+    //
+    _count = -1;
+}
diff --git a/cpp/src/IceUtil/Thread.cpp b/cpp/src/IceUtil/Thread.cpp
index 717ccb66622..6648c22da1d 100644
--- a/cpp/src/IceUtil/Thread.cpp
+++ b/cpp/src/IceUtil/Thread.cpp
@@ -307,34 +307,3 @@ IceUtil::Thread::operator<(const Thread& rhs) const
 
 #endif
 
-#ifdef never
-void ice_atomic_inc(ice_atomic_t *v)
-{
-    __asm__ __volatile__(
-	"lock ; incl %0"
-	:"=m" (v->counter)
-	:"m" (v->counter));
-}
-
-int ice_atomic_dec_and_test(ice_atomic_t *v)
-{
-    
-    unsigned char c;
-    __asm__ __volatile__(
-	"lock ; decl %0; sete %1"
-	:"=m" (v->counter), "=qm" (c)
-	:"m" (v->counter) : "memory");
-    return c != 0;
-}
-
-int ice_atomic_exchange_add(int i, ice_atomic_t* v)
-{
-    int tmp = i;
-    __asm__ __volatile__(
-	"lock ; xadd %0,(%2)"
-	:"+r"(tmp), "=m"(v->counter)
-	:"r"(v), "m"(v->counter)
-	: "memory");
-    return tmp + i;
-}
-#endif