diff --git a/base-linux/include/base/platform_env.h b/base-linux/include/base/platform_env.h
index d485c88555..8611b9c921 100644
--- a/base-linux/include/base/platform_env.h
+++ b/base-linux/include/base/platform_env.h
@@ -199,12 +199,12 @@ namespace Genode {
 					/**
 					 * Map dataspace into local address space
 					 */
-					static void *_map_local(Dataspace_capability ds,
-					                        Genode::size_t       size,
-					                        addr_t               offset,
-					                        bool                 use_local_addr,
-					                        addr_t               local_addr,
-					                        bool                 executable);
+					void *_map_local(Dataspace_capability ds,
+					                 Genode::size_t       size,
+					                 addr_t               offset,
+					                 bool                 use_local_addr,
+					                 addr_t               local_addr,
+					                 bool                 executable);
 
 					/**
 					 * Determine size of dataspace
@@ -214,17 +214,17 @@ namespace Genode {
 					 * dataspace size is determined via an RPC to core
 					 * (calling 'Dataspace::size()').
 					 */
-					static size_t _dataspace_size(Capability<Dataspace>);
+					size_t _dataspace_size(Capability<Dataspace>);
 
 					/**
 					 * Determine file descriptor of dataspace
 					 */
-					static int _dataspace_fd(Capability<Dataspace>);
+					int _dataspace_fd(Capability<Dataspace>);
 
 					/**
 					 * Determine whether dataspace is writable
 					 */
-					static bool _dataspace_writable(Capability<Dataspace>);
+					bool _dataspace_writable(Capability<Dataspace>);
 
 				public:
 
diff --git a/base-linux/src/core/platform.cc b/base-linux/src/core/platform.cc
index 6906e46a94..ed402d06c7 100644
--- a/base-linux/src/core/platform.cc
+++ b/base-linux/src/core/platform.cc
@@ -111,8 +111,13 @@ Platform_env_base::Rm_session_mmap::_dataspace_size(Capability<Dataspace> ds_cap
 		return Dataspace_capability::deref(ds_cap)->size();
 
 	/* use RPC if called from a different thread */
-	if (!core_env()->entrypoint()->is_myself())
-		return Dataspace_client(ds_cap).size();
+	if (!core_env()->entrypoint()->is_myself()) {
+		/* release Rm_session_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 */
 	Dataspace *ds = core_env()->entrypoint()->lookup(ds_cap);
@@ -122,8 +127,13 @@ Platform_env_base::Rm_session_mmap::_dataspace_size(Capability<Dataspace> ds_cap
 
 int Platform_env_base::Rm_session_mmap::_dataspace_fd(Capability<Dataspace> ds_cap)
 {
-	if (!core_env()->entrypoint()->is_myself())
-		return Linux_dataspace_client(ds_cap).fd().dst().socket;
+	if (!core_env()->entrypoint()->is_myself()) {
+		/* release Rm_session_mmap::_lock during RPC */
+		_lock.unlock();
+		int socket = Linux_dataspace_client(ds_cap).fd().dst().socket;
+		_lock.lock();
+		return socket;
+	}
 
 	Capability<Linux_dataspace> lx_ds_cap = static_cap_cast<Linux_dataspace>(ds_cap);
 
@@ -135,8 +145,13 @@ int Platform_env_base::Rm_session_mmap::_dataspace_fd(Capability<Dataspace> ds_c
 
 bool Platform_env_base::Rm_session_mmap::_dataspace_writable(Dataspace_capability ds_cap)
 {
-	if (!core_env()->entrypoint()->is_myself())
-		return Dataspace_client(ds_cap).writable();
+	if (!core_env()->entrypoint()->is_myself()) {
+		/* release Rm_session_mmap::_lock during RPC */
+		_lock.unlock();
+		bool writable = Dataspace_client(ds_cap).writable();
+		_lock.lock();
+		return writable;
+	}
 
 	Dataspace *ds = core_env()->entrypoint()->lookup(ds_cap);