diff --git a/repos/base-linux/src/core/platform.cc b/repos/base-linux/src/core/platform.cc
index d32695bfc..cd488eb78 100644
--- a/repos/base-linux/src/core/platform.cc
+++ b/repos/base-linux/src/core/platform.cc
@@ -187,15 +187,6 @@ size_t Region_map_mmap::_dataspace_size(Capability<Dataspace> ds_cap)
 	if (!ds_cap.valid())
 		return Local_capability<Dataspace>::deref(ds_cap)->size();
 
-	/* use RPC if called from a different thread */
-	if (!core_env()->entrypoint()->is_myself()) {
-		/* release Region_map_mmap::_lock during RPC */
-		_lock.unlock();
-		Genode::size_t size = Dataspace_client(ds_cap).size();
-		_lock.lock();
-		return size;
-	}
-
 	/* use local function call if called from the entrypoint */
 	return core_env()->entrypoint()->apply(ds_cap, [] (Dataspace *ds) {
 		return ds ? ds->size() : 0; });
@@ -204,15 +195,6 @@ size_t Region_map_mmap::_dataspace_size(Capability<Dataspace> ds_cap)
 
 int Region_map_mmap::_dataspace_fd(Capability<Dataspace> ds_cap)
 {
-	if (!core_env()->entrypoint()->is_myself()) {
-		/* release Region_map_mmap::_lock during RPC */
-		_lock.unlock();
-		Untyped_capability fd_cap = Linux_dataspace_client(ds_cap).fd();
-		int socket = Capability_space::ipc_cap_data(fd_cap).dst.socket;
-		_lock.lock();
-		return socket;
-	}
-
 	Capability<Linux_dataspace> lx_ds_cap = static_cap_cast<Linux_dataspace>(ds_cap);
 
 	/*
@@ -231,14 +213,6 @@ int Region_map_mmap::_dataspace_fd(Capability<Dataspace> ds_cap)
 
 bool Region_map_mmap::_dataspace_writable(Dataspace_capability ds_cap)
 {
-	if (!core_env()->entrypoint()->is_myself()) {
-		/* release Region_map_mmap::_lock during RPC */
-		_lock.unlock();
-		bool writable = Dataspace_client(ds_cap).writable();
-		_lock.lock();
-		return writable;
-	}
-
 	return core_env()->entrypoint()->apply(ds_cap, [] (Dataspace *ds) {
 		return ds ? ds->writable() : false; });
 }
diff --git a/repos/base-linux/src/include/base/internal/region_map_mmap.h b/repos/base-linux/src/include/base/internal/region_map_mmap.h
index 29da3c4b3..37c0f79f8 100644
--- a/repos/base-linux/src/include/base/internal/region_map_mmap.h
+++ b/repos/base-linux/src/include/base/internal/region_map_mmap.h
@@ -35,7 +35,6 @@ class Genode::Region_map_mmap : public Region_map, public Dataspace
 {
 	private:
 
-		Lock            _lock;    /* protect '_rmap' */
 		Region_registry _rmap;
 		bool      const _sub_rm;  /* false if region map is root */
 		size_t    const _size;
diff --git a/repos/base-linux/src/lib/base/region_map_mmap.cc b/repos/base-linux/src/lib/base/region_map_mmap.cc
index 6af7d6520..915dde73d 100644
--- a/repos/base-linux/src/lib/base/region_map_mmap.cc
+++ b/repos/base-linux/src/lib/base/region_map_mmap.cc
@@ -60,6 +60,16 @@ static bool is_sub_rm_session(Dataspace_capability ds)
 }
 
 
+/**
+ * Lock for protecting mmap/unmap sequences and region-map meta data
+ */
+static Lock &lock()
+{
+	static Lock lock;
+	return lock;
+}
+
+
 addr_t Region_map_mmap::_reserve_local(bool           use_local_addr,
                                        addr_t         local_addr,
                                        Genode::size_t size)
@@ -164,7 +174,7 @@ Region_map::Local_addr Region_map_mmap::attach(Dataspace_capability ds,
                                                Region_map::Local_addr local_addr,
                                                bool executable)
 {
-	Lock::Guard lock_guard(_lock);
+	Lock::Guard lock_guard(lock());
 
 	/* only support attach_at for sub RM sessions */
 	if (_sub_rm && !use_local_addr) {
@@ -306,7 +316,7 @@ Region_map::Local_addr Region_map_mmap::attach(Dataspace_capability ds,
 
 void Region_map_mmap::detach(Region_map::Local_addr local_addr)
 {
-	Lock::Guard lock_guard(_lock);
+	Lock::Guard lock_guard(lock());
 
 	/*
 	 * Cases
diff --git a/repos/base/src/lib/base/thread.cc b/repos/base/src/lib/base/thread.cc
index cfa662761..189f3ef1e 100644
--- a/repos/base/src/lib/base/thread.cc
+++ b/repos/base/src/lib/base/thread.cc
@@ -77,14 +77,6 @@ void Stack::size(size_t const size)
 Stack *
 Thread::_alloc_stack(size_t stack_size, char const *name, bool main_thread)
 {
-	/*
-	 * Synchronize stack list when creating new threads from multiple threads
-	 *
-	 * XXX: remove interim fix
-	 */
-	static Lock alloc_lock;
-	Lock::Guard _lock_guard(alloc_lock);
-
 	/* allocate stack */
 	Stack *stack = Stack_allocator::stack_allocator().alloc(this, main_thread);
 	if (!stack)