base-hw: handle cap-slab exhaust in Thread::start

This interim solution for issue #5256 solves the problem for the
thread.run script.

Issue #5256

repos/base-hw/include/hw_native_pd/client.h

@@ -27,6 +27,9 @@ struct Genode::Hw_native_pd_client : Rpc_client<Pd_session::Native_pd>
 
 	void upgrade_cap_slab() override {
 		call<Rpc_upgrade_cap_slab>(); }
+
+	size_t avail_cap_slab() override {
+		return call<Rpc_avail_cap_slab>(); }
 };
 
 #endif /* _INCLUDE__HW_NATIVE_PD__CLIENT_H_ */

repos/base-hw/include/hw_native_pd/hw_native_pd.h

@@ -21,6 +21,7 @@
 struct Genode::Pd_session::Native_pd : Interface
 {
 	virtual void upgrade_cap_slab() = 0;
+	virtual size_t avail_cap_slab() = 0;
 
 
 	/*********************
@@ -29,7 +30,8 @@ struct Genode::Pd_session::Native_pd : Interface
 
 	GENODE_RPC_THROW(Rpc_upgrade_cap_slab, void, upgrade_cap_slab,
 	                 GENODE_TYPE_LIST(Out_of_ram, Out_of_caps));
-	GENODE_RPC_INTERFACE(Rpc_upgrade_cap_slab);
+	GENODE_RPC(Rpc_avail_cap_slab, size_t, avail_cap_slab);
+	GENODE_RPC_INTERFACE(Rpc_upgrade_cap_slab, Rpc_avail_cap_slab);
 };
 
 #endif /* _INCLUDE__HW_NATIVE_PD__HW_NATIVE_PD_H_ */

repos/base-hw/src/core/native_pd_component.cc

@@ -23,6 +23,12 @@ void Native_pd_component::upgrade_cap_slab()
 }
 
 
+size_t Native_pd_component::avail_cap_slab()
+{
+	return _pd_session._pd->avail_slab();
+}
+
+
 Native_pd_component::Native_pd_component(Pd_session_component &pd, char const *)
 :
 	_pd_session(pd)

repos/base-hw/src/core/native_pd_component.h

@@ -41,6 +41,7 @@ class Core::Native_pd_component : public Rpc_object<Pd_session::Native_pd>
 		~Native_pd_component();
 
 		void upgrade_cap_slab() override;
+		size_t avail_cap_slab() override;
 };
 
 #endif /* _CORE__INCLUDE__NATIVE_PD_COMPONENT_H_ */

repos/base-hw/src/core/platform_pd.h

@@ -163,6 +163,7 @@ class Core::Cap_space
 		Cap_slab & capability_slab() { return _slab; }
 
 		void upgrade_slab(Allocator &alloc);
+		size_t avail_slab() { return _slab.avail_entries(); }
 };
 
 
@@ -208,6 +209,7 @@ class Core::Platform_pd : public Hw::Address_space, private Cap_space
 
 		using Cap_space::capability_slab;
 		using Cap_space::upgrade_slab;
+		using Cap_space::avail_slab;
 
 		/**
 		 * Bind thread to protection domain

repos/base-hw/src/include/base/internal/native_env.h

@@ -14,12 +14,16 @@
 #ifndef _INCLUDE__BASE__INTERNAL__NATIVE_ENV_H_
 #define _INCLUDE__BASE__INTERNAL__NATIVE_ENV_H_
 
+#include <base/stdint.h>
+
 namespace Genode {
 
 	/**
 	 * Upgrade quota of the PD session's capability slab allocator
 	 */
 	void upgrade_capability_slab();
+
+	size_t avail_capability_slab();
 };
 
 #endif /* _INCLUDE__BASE__INTERNAL__NATIVE_ENV_H_ */

repos/base-hw/src/lib/base/capability_slab.cc

@@ -32,6 +32,12 @@ void Genode::init_cap_slab(Pd_session &pd, Parent &parent)
 }
 
 
+size_t Genode::avail_capability_slab()
+{
+	return native_pd_ptr ? native_pd_ptr->avail_cap_slab() : 0UL;
+}
+
+
 void Genode::upgrade_capability_slab()
 {
 	if (!native_pd_ptr || !parent_ptr) {

repos/base-hw/src/lib/base/thread_start.cc

@@ -22,6 +22,7 @@
 /* base-internal includes */
 #include <base/internal/stack_allocator.h>
 #include <base/internal/native_utcb.h>
+#include <base/internal/native_env.h>
 #include <base/internal/globals.h>
 
 using namespace Genode;
@@ -106,6 +107,9 @@ void Thread::_deinit_platform_thread()
 
 Thread::Start_result Thread::start()
 {
+	while (avail_capability_slab() < 5)
+		upgrade_capability_slab();
+
 	return _thread_cap.convert<Start_result>(
 		[&] (Thread_capability cap) {
 			Cpu_thread_client cpu_thread(cap);