diff --git a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/internal/pdom/tests/PDOMBugsTest.java b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/internal/pdom/tests/PDOMBugsTest.java
index 1b1d79a1805..b07a836d4db 100644
--- a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/internal/pdom/tests/PDOMBugsTest.java
+++ b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/internal/pdom/tests/PDOMBugsTest.java
@@ -120,4 +120,58 @@ public class PDOMBugsTest extends BaseTestCase {
 			pdom.releaseReadLock();
 		}
 	}
+	
+	public void testInterruptingAcquireReadLock() throws Exception {
+		final PDOM pdom= (PDOM) CCoreInternals.getPDOMManager().getPDOM(cproject);
+		final boolean[] ok= {false};
+		pdom.acquireWriteLock();
+		try {
+			Thread other= new Thread() {
+				public void run() {
+					try {
+						pdom.acquireReadLock();
+					} catch (InterruptedException e) {
+						ok[0]= true;
+					} 
+				}
+			};
+			other.start();
+			other.interrupt();
+			other.join();
+			assertTrue("thread was not interrupted", ok[0]);
+		}
+		finally {
+			pdom.releaseWriteLock();
+		}
+		pdom.acquireWriteLock();
+		pdom.releaseWriteLock();
+	}
+	
+	public void testInterruptingAcquireWriteLock() throws Exception {
+		final PDOM pdom= (PDOM) CCoreInternals.getPDOMManager().getPDOM(cproject);
+		final boolean[] ok= {false};
+		pdom.acquireReadLock();
+		try {
+			Thread other= new Thread() {
+				public void run() {
+					try {
+						pdom.acquireReadLock();
+						pdom.acquireWriteLock(1);
+					} catch (InterruptedException e) {
+						ok[0]= true;
+						pdom.releaseReadLock();
+					} 
+				}
+			};
+			other.start();
+			other.interrupt();
+			other.join();
+			assertTrue("thread was not interrupted", ok[0]);
+		}
+		finally {
+			pdom.releaseReadLock();
+		}
+		pdom.acquireWriteLock();
+		pdom.releaseWriteLock();
+	}
 }
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/pdom/PDOM.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/pdom/PDOM.java
index 8ae4a6ddc5d..a2b94dc7f31 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/pdom/PDOM.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/pdom/PDOM.java
@@ -504,9 +504,13 @@ public class PDOM extends PlatformObject implements IIndexFragment, IPDOM {
 	public void acquireReadLock() throws InterruptedException {
 		synchronized (mutex) {
 			++waitingReaders;
-			while (lockCount < 0)
-				mutex.wait();
-			--waitingReaders;
+			try {
+				while (lockCount < 0)
+					mutex.wait();
+			}
+			finally {
+				--waitingReaders;
+			}
 			++lockCount;
 		}
 	}
@@ -530,18 +534,18 @@ public class PDOM extends PlatformObject implements IIndexFragment, IPDOM {
 			if (giveupReadLocks > 0) {
 				// giveup on read locks
 				assert lockCount >= giveupReadLocks: "Not enough locks to release"; //$NON-NLS-1$
-				if (lockCount >= giveupReadLocks) {
-					lockCount-= giveupReadLocks;
-				}
-				else if (lockCount >= 0) {
-					lockCount= 0;
+				if (lockCount < giveupReadLocks) {
+					giveupReadLocks= lockCount;
 				}
 			}
+			else {
+				giveupReadLocks= 0;
+			}
 
 			// Let the readers go first
-			while (lockCount != 0 || waitingReaders > 0)
+			while (lockCount > giveupReadLocks || waitingReaders > 0)
 				mutex.wait();
-			--lockCount;
+			lockCount= -1;
 			db.setWritable();
 		}
 	}