base: setup parent upgrade mechanism eagerly

Fix #2447

repos/base-linux/src/include/base/internal/local_parent.h

@@ -65,9 +65,7 @@ class Genode::Local_parent : public Expanding_parent_client
 		 *                    promote requests to non-local
 		 *                    services
 		 */
-		Local_parent(Parent_capability parent_cap,
+		Local_parent(Parent_capability parent_cap, Allocator &);
-		             Emergency_ram_reserve &,
-		             Allocator &);
 };
 
 #endif /* _INCLUDE__BASE__INTERNAL__LOCAL_PARENT_H_ */

repos/base-linux/src/include/base/internal/platform_env.h

@@ -101,8 +101,7 @@ class Genode::Platform_env_base : public Env_deprecated
 /**
  * 'Platform_env' used by all processes except for core
  */
-class Genode::Platform_env : public Platform_env_base,
+class Genode::Platform_env : public Platform_env_base
-                             public Expanding_parent_client::Emergency_ram_reserve
 {
 	private:
 
@@ -113,14 +112,6 @@ class Genode::Platform_env : public Platform_env_base,
 
 		Heap _heap;
 
-		/*
-		 * Emergency RAM reserve
-		 *
-		 * See the comment of '_fallback_sig_cap()' in 'env/env.cc'.
-		 */
-		constexpr static size_t  _emergency_ram_size() { return 8*1024; }
-		Ram_dataspace_capability _emergency_ram_ds;
-
 		/**
 		 * Attach stack area to local address space (for non-hybrid components)
 		 */
@@ -139,13 +130,6 @@ class Genode::Platform_env : public Platform_env_base,
 		~Platform_env() { _parent().exit(0); }
 
 
-		/*************************************
-		 ** Emergency_ram_reserve interface **
-		 *************************************/
-
-		void release() { ram_session()->free(_emergency_ram_ds); }
-
-
 		/******************************
 		 ** Env_deprecated interface **
 		 ******************************/

repos/base-linux/src/lib/base/platform_env.cc

@@ -101,10 +101,9 @@ Parent::Close_result Local_parent::close(Client::Id id)
 
 
 Local_parent::Local_parent(Parent_capability parent_cap,
-                           Emergency_ram_reserve &reserve,
                            Allocator &alloc)
 :
-	Expanding_parent_client(parent_cap, reserve), _alloc(alloc)
+	Expanding_parent_client(parent_cap), _alloc(alloc)
 { }
 
 
@@ -148,7 +147,7 @@ static Parent_capability obtain_parent_cap()
 
 Local_parent &Platform_env::_parent()
 {
-	static Local_parent local_parent(obtain_parent_cap(), *this, _heap);
+	static Local_parent local_parent(obtain_parent_cap(), _heap);
 	return local_parent;
 }
 
@@ -157,8 +156,7 @@ Platform_env::Platform_env()
 :
 	Platform_env_base(static_cap_cast<Cpu_session>(_parent().session_cap(Parent::Env::cpu())),
 	                  static_cap_cast<Pd_session> (_parent().session_cap(Parent::Env::pd()))),
-	_heap(Platform_env_base::ram_session(), Platform_env_base::rm_session()),
+	_heap(Platform_env_base::ram_session(), Platform_env_base::rm_session())
-	_emergency_ram_ds(ram_session()->alloc(_emergency_ram_size()))
 {
 	_attach_stack_area();
 

repos/base/src/core/main.cc

@@ -92,6 +92,12 @@ Platform_generic *Genode::platform() { return platform_specific(); }
 Thread_capability Genode::main_thread_cap() { return Thread_capability(); }
 
 
+/**
+ * Dummy implementation for core that has no parent to ask for resources
+ */
+void Genode::init_parent_resource_requests(Genode::Env & env) {};
+
+
 /****************
  ** Core child **
  ****************/

repos/base/src/include/base/internal/expanding_parent_client.h

@@ -28,13 +28,6 @@ namespace Genode { class Expanding_parent_client; }
 
 class Genode::Expanding_parent_client : public Parent_client
 {
-	public:
-
-		struct Emergency_ram_reserve
-		{
-			virtual void release() = 0;
-		};
-
 	private:
 
 		/**
@@ -58,29 +51,43 @@ class Genode::Expanding_parent_client : public Parent_client
 		Lock _lock;
 
 		/**
-		 * Return signal context capability for the fallback signal handler
+		 * Signal context for the fallback signal handler
 		 */
-		Signal_context_capability _fallback_sig_cap();
+		Signal_context _fallback_sig_ctx;
+
+		/**
+		 * Signal context capability for the fallback signal handler
+		 */
+		Signal_context_capability _fallback_sig_cap;
+
+		/**
+		 * Signal receiver for the fallback signal handler
+		 */
+		Constructible<Signal_receiver> _fallback_sig_rcv;
 
 		/**
 		 * Block for resource response arriving at the fallback signal handler
 		 */
-		static void _wait_for_resource_response();
+		void _wait_for_resource_response() {
-
+			_fallback_sig_rcv->wait_for_signal(); }
-		/**
-		 * Emergency RAM reserve for constructing the fallback signal handler
-		 *
-		 * See the comment of '_fallback_sig_cap()' in 'env/env.cc'.
-		 */
-		Emergency_ram_reserve &_emergency_ram_reserve;
 
 	public:
 
-		Expanding_parent_client(Parent_capability cap,
+		Expanding_parent_client(Parent_capability cap)
-		                        Emergency_ram_reserve &emergency_ram_reserve)
+		: Parent_client(cap) { }
-		:
+
-			Parent_client(cap), _emergency_ram_reserve(emergency_ram_reserve)
+
-		{ }
+		/**
+		 * Downstreamed construction of the fallback signaling, used
+		 * when the environment is ready to construct a signal receiver
+		 */
+		void init_fallback_signal_handling()
+		{
+			if (!_fallback_sig_cap.valid()) {
+				_fallback_sig_rcv.construct();
+				_fallback_sig_cap = _fallback_sig_rcv->manage(&_fallback_sig_ctx);
+			}
+		}
 
 
 		/**********************
@@ -168,7 +175,7 @@ class Genode::Expanding_parent_client : public Parent_client
 			 * Install fallback signal handler not yet installed.
 			 */
 			if (_state == UNDEFINED) {
-				Parent_client::resource_avail_sigh(_fallback_sig_cap());
+				Parent_client::resource_avail_sigh(_fallback_sig_cap);
 				_state = BLOCKING_DEFAULT;
 			}
 

repos/base/src/include/base/internal/globals.h

@@ -36,6 +36,7 @@ namespace Genode {
 	void init_signal_thread(Env &);
 	void init_root_proxy(Env &);
 	void init_log();
+	void init_parent_resource_requests(Env &);
 	void exec_static_constructors();
 
 	void destroy_signal_thread();

repos/base/src/include/base/internal/platform_env.h

@@ -42,8 +42,7 @@ namespace Genode {
 }
 
 
-class Genode::Platform_env : public Platform_env_base,
+class Genode::Platform_env : public Platform_env_base
-                             public Expanding_parent_client::Emergency_ram_reserve
 {
 	private:
 
@@ -81,14 +80,6 @@ class Genode::Platform_env : public Platform_env_base,
 		 */
 		Attached_stack_area _stack_area { _parent_client, _resources.pd };
 
-		/*
-		 * Emergency RAM reserve
-		 *
-		 * See the comment of '_fallback_sig_cap()' in 'env/env.cc'.
-		 */
-		constexpr static size_t  _emergency_ram_size() { return 16*1024; }
-		Ram_dataspace_capability _emergency_ram_ds;
-
 	public:
 
 		/**
@@ -96,10 +87,9 @@ class Genode::Platform_env : public Platform_env_base,
 		 */
 		Platform_env()
 		:
-			_parent_client(Genode::parent_cap(), *this),
+			_parent_client(Genode::parent_cap()),
 			_resources(_parent_client),
-			_heap(&_resources.pd, &_resources.rm, Heap::UNLIMITED),
+			_heap(&_resources.pd, &_resources.rm, Heap::UNLIMITED)
-			_emergency_ram_ds(_resources.pd.alloc(_emergency_ram_size()))
 		{
 			env_stack_area_ram_allocator = &_resources.pd;
 			env_stack_area_region_map    = &_stack_area;
@@ -112,18 +102,6 @@ class Genode::Platform_env : public Platform_env_base,
 		void reinit_main_thread(Capability<Region_map> &) override;
 
 
-		/*************************************
-		 ** Emergency_ram_reserve interface **
-		 *************************************/
-
-		void release()
-		{
-			log("used before freeing emergency=", _resources.pd.used_ram());
-			_resources.pd.free(_emergency_ram_ds);
-			log("used after freeing emergency=", _resources.pd.used_ram());
-		}
-
-
 		/******************************
 		 ** Env_deprecated interface **
 		 ******************************/

repos/base/src/lib/base/entrypoint.cc

@@ -274,6 +274,12 @@ namespace {
 			Genode::call_global_static_constructors();
 			Genode::init_signal_transmitter(env);
 
+			/*
+			 * Now, as signaling is available, initialize the asynchronous
+			 * parent resource mechanism
+			 */
+			init_parent_resource_requests(env);
+
 			Component::construct(env);
 		}
 	};

repos/base/src/lib/base/env_deprecated.cc

@@ -34,47 +34,12 @@ namespace Genode {
 }
 
 
-static Genode::Signal_receiver *resource_sig_rec()
+void Genode::init_parent_resource_requests(Genode::Env & env)
 {
-	static Genode::Signal_receiver sig_rec;
+	/**
-	return &sig_rec;
+	 * Catch up asynchronous resource request and notification
-}
+	 * mechanism construction of the expanding parent environment
-
+	 */
-
+	using Parent = Expanding_parent_client;
-Genode::Signal_context_capability
+	static_cast<Parent*>(&env.parent())->init_fallback_signal_handling();
-Genode::Expanding_parent_client::_fallback_sig_cap()
-{
-	static Signal_context            _sig_ctx;
-	static Signal_context_capability _sig_cap;
-
-	/* create signal-context capability only once */
-	if (!_sig_cap.valid()) {
-
-		/*
-		 * Because the 'manage' function consumes meta data of the signal
-		 * session, calling it may result in an 'Out_of_ram' or 'Out_of_caps' error.
-		 * The 'manage' function handles this error by upgrading the session quota
-		 * accordingly. However, this upgrade, in turn, may result in the
-		 * depletion of the process' RAM quota. In this case, the process would
-		 * issue a resource request to the parent. But in order to do so, the
-		 * fallback signal handler has to be constructed. To solve this
-		 * hen-and-egg problem, we allocate a so-called emergency RAM reserve
-		 * immediately at the startup of the process as part of the
-		 * 'Platform_env'. When initializing the fallback signal handler, these
-		 * resources get released in order to ensure an eventual upgrade of the
-		 * signal session to succeed.
-		 *
-		 * The corner case is tested by 'os/src/test/resource_request'.
-		 */
-		_emergency_ram_reserve.release();
-		_sig_cap = resource_sig_rec()->manage(&_sig_ctx);
-	}
-
-	return _sig_cap;
-}
-
-
-void Genode::Expanding_parent_client::_wait_for_resource_response()
-{
-	resource_sig_rec()->wait_for_signal();
 }

repos/base/src/lib/base/env_reinit.cc

@@ -59,7 +59,7 @@ void Genode::Platform_env::reinit(Native_capability::Raw raw)
 	 * Re-initialize 'Platform_env' members
 	 */
 	Expanding_parent_client * const p = &_parent_client;
-	construct_at<Expanding_parent_client>(p, parent_cap(), *this);
+	construct_at<Expanding_parent_client>(p, parent_cap());
 	construct_at<Resources>(&_resources, _parent_client);
 
 	/*