rump: Stabilize rump libs and fs server

* Perform sanity check before calculating memory available to rump kernel
* Distinguish between 'Hard_context' and 'Hard_context_thread', so no dead
  threads (that will not be started) are created
* Install signal-handler for memory-resource requests. This way the fs server
  will not block forever when the quota is execeeded and a resource requests
  fails, leaving the rump kernels to perform necessary actions

Fixes #1127

dde_rump/include/util/allocator_fap.h

@@ -88,11 +88,11 @@ namespace Allocator {
 					/* lookup phys. address */
 					_ds_phys[_index] = Genode::Dataspace_client(_ds_cap[_index]).phys_addr();
 				} catch (Genode::Ram_session::Quota_exceeded) {
-					PERR("Backend allocator exhausted");
+					PWRN("Backend allocator exhausted");
 					_quota_exceeded = true;
 					return false;
 				} catch (Genode::Rm_session::Attach_failed) {
-					PERR("Backend VM region exhausted");
+					PWRN("Backend VM region exhausted");
 					_quota_exceeded = true;
 					return false;
 				}
@@ -116,7 +116,7 @@ namespace Allocator {
 			}
 
 			/**
-			 * Allocate 
+			 * Allocate
 			 */
 			bool alloc(size_t size, void **out_addr)
 			{
@@ -126,10 +126,8 @@ namespace Allocator {
 					return done;
 
 				done = _alloc_block();
-				if (!done) {
-					PERR("Backend allocator exhausted\n");
+				if (!done)
 					return false;
-				}
 
 				return _range.alloc(size, out_addr);
 			}

dde_rump/include/util/hard_context.h

@@ -33,14 +33,33 @@ namespace Timer {
 	class Connection;
 };
 
-class Hard_context : public Genode::Thread<sizeof(Genode::addr_t) * 2048>
+
+class Hard_context
 {
 	private:
 
-		func                      _func;
-		void                     *_arg;
-		int                       _cookie;
-		lwp                      *_lwp;
+		int  _cookie;
+		lwp *_lwp     = 0;
+
+	public:
+
+		Hard_context(int cookie)
+		: _cookie(cookie){ }
+
+		void set_lwp(lwp *l) { _lwp = l; }
+		lwp *get_lwp() { return _lwp; }
+
+		static Timer::Connection *timer();
+};
+
+
+class Hard_context_thread : public Hard_context,
+                            public Genode::Thread<sizeof(Genode::addr_t) * 2048>
+{
+	private:
+
+		func  _func;
+		void *_arg;
 
 	protected:
 
@@ -52,14 +71,10 @@ class Hard_context : public Genode::Thread<sizeof(Genode::addr_t) * 2048>
 
 	public:
 
-		Hard_context(char const *name, func f, void *arg, int cookie, bool run = true)
-		: Thread(name),
-			_func(f), _arg(arg), _cookie(cookie), _lwp(0) { if (run) start(); }
-
-		void set_lwp(lwp *l) { _lwp = l; }
-		lwp *get_lwp() { return _lwp; }
-
-		static Timer::Connection *timer();
+		Hard_context_thread(char const *name, func f, void *arg, int cookie, bool run = true)
+		: Hard_context(cookie), Thread(name),
+			_func(f), _arg(arg) { if (run) start(); }
 };
 
+
 #endif /* _INCLUDE__HARD_CONTEXT_H_ */

dde_rump/src/lib/rump/hypercall.cc

@@ -61,7 +61,7 @@ int rumpuser_init(int version, const struct rumpuser_hyperup *hyp)
  ** Threads **
  *************/
 
-static Hard_context _main_thread("main thread", 0, 0, 0, false);
+static Hard_context _main_thread(0);
 
 static Hard_context *myself()
 {
@@ -108,7 +108,7 @@ int rumpuser_thread_create(func f, void *arg, const char *name,
 	if (mustjoin)
 		*cookie = (void *)++count;
 
-	new (Genode::env()->heap()) Hard_context(name, f, arg, mustjoin ? count : 0);
+	new (Genode::env()->heap()) Hard_context_thread(name, f, arg, mustjoin ? count : 0);
 
 	return 0;
 }
@@ -123,6 +123,8 @@ void rumpuser_seterrno(int e) { errno = e; }
 
 int rumpuser_getparam(const char *name, void *buf, size_t buflen)
 {
+	enum { RESERVE_MEM = 2U * 1024 * 1024 };
+
 	/* support one cpu */
 	PDBG("%s", name);
 	if (!Genode::strcmp(name, "_RUMPUSER_NCPU")) {
@@ -139,11 +141,18 @@ int rumpuser_getparam(const char *name, void *buf, size_t buflen)
 	if (!Genode::strcmp(name, "RUMP_MEMLIMIT")) {
 
 		/* leave 2 MB for the Genode */
-		size_t rump_ram =  Genode::env()->ram_session()->avail() - (2 * 1024 * 1024);
+		size_t rump_ram =  Genode::env()->ram_session()->avail();
+
+		if (rump_ram <= RESERVE_MEM) {
+			PERR("Insufficient quota need left: %zu < %u bytes", rump_ram, RESERVE_MEM);
+			return -1;
+		}
+
+		rump_ram -= RESERVE_MEM;
 
 		/* convert to string */
 		Genode::snprintf((char *)buf, buflen, "%zu", rump_ram);
-		PINF("Asserting rump kernel %zu KB of RAM", rump_ram / 1024);
+		PERR("Asserting rump kernel %zu KB of RAM", rump_ram / 1024);
 		return 0;
 	}
 

dde_rump/src/lib/rump/io.cc

@@ -39,7 +39,7 @@ struct Packet : Genode::List<Packet>::Element
 };
 
 
-class Backend : public Hard_context
+class Backend : public Hard_context_thread
 {
 
 	private:
@@ -211,7 +211,7 @@ class Backend : public Hard_context
 	public:
 
 		Backend()
-		: Hard_context("block_io", 0, 0, 0, false),
+		: Hard_context_thread("block_io", 0, 0, 0, false),
 		_alloc(Genode::env()->heap()),
 		_session(&_alloc),
 		_alloc_sem(COUNT),

dde_rump/src/server/rump_fs/main.cc

@@ -426,7 +426,8 @@ class File_system::Root : public Root_component<Session_component>
 
 struct File_system::Main
 {
-	Server::Entrypoint &ep;
+	Server::Entrypoint             &ep;
+	Server::Signal_rpc_member<Main> resource_dispatcher;
 
 	/*
 	 * Initialize root interface
@@ -436,12 +437,17 @@ struct File_system::Main
 	Root fs_root = { ep, sliced_heap };
 
 
+	/* return immediately from resource requests */
+	void resource_handler(unsigned) { }
+
 	Main(Server::Entrypoint &ep)
 		:
-			ep(ep)
+			ep(ep),
+			resource_dispatcher(ep, *this, &Main::resource_handler)
 	{
 		File_system::init(ep);
 		env()->parent()->announce(ep.manage(fs_root));
+		env()->parent()->resource_avail_sigh(resource_dispatcher);
 	}
 };