hw: implement priority-based scheduling (fix #945)

base-hw/src/core/include/platform_thread.h

@@ -52,6 +52,7 @@ namespace Genode {
 		Ram_dataspace_capability _utcb;
 		char                     _name[NAME_MAX_LEN];
 		char                     _kernel_thread[sizeof(Kernel::Thread)];
+		unsigned                 _priority;
 
 		/*
 		 * Wether this thread is the main thread of a program.
@@ -196,6 +197,8 @@ namespace Genode {
 			bool main_thread() const { return _main_thread; }
 
 			Tlb * tlb() const { return _tlb; }
+
+			unsigned priority() { return _priority; }
 	};
 }
 

base-hw/src/core/kernel.cc

@@ -125,7 +125,11 @@ namespace Kernel
 			 */
 			Vm(Genode::Cpu_state_modes * const state,
 			   Signal_context * const context)
-			: _state(state), _context(context) { }
+			: _state(state), _context(context)
+			{
+				/* set VM to least priority by now */
+				priority = 0;
+			}
 
 
 			/**************************

base-hw/src/core/kernel/priority.h

@@ -0,0 +1,46 @@
+/*
+ * \brief   Priority definition for scheduling
+ * \author  Stefan Kalkowski
+ * \date    2013-11-08
+ */
+
+/*
+ * Copyright (C) 2013 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+#ifndef _KERNEL__PRIORITY_H_
+#define _KERNEL__PRIORITY_H_
+
+#include <util/misc_math.h>
+
+namespace Kernel
+{
+	class Priority;
+}
+
+
+class Kernel::Priority
+{
+	private:
+
+		unsigned _prio;
+
+	public:
+
+		enum { MAX = 255 };
+
+		Priority(unsigned prio = MAX) : _prio(Genode::min(prio, MAX)) { }
+
+		Priority &operator=(unsigned const &prio)
+		{
+			_prio = Genode::min(prio, MAX);
+			return *this;
+		}
+
+		operator unsigned() const { return _prio; }
+};
+
+#endif /* _KERNEL__PRIORITY_H_ */

base-hw/src/core/kernel/scheduler.h

@@ -15,6 +15,7 @@
 #define _KERNEL__SCHEDULER_H_
 
 /* core includes */
+#include <kernel/priority.h>
 #include <assert.h>
 
 namespace Kernel
@@ -155,34 +156,44 @@ class Kernel::Scheduler
 		/**
 		 * Capability to be item in a scheduler through inheritance
 		 */
-		class Item : public Double_list<T>::Item { };
+		struct Item : public Double_list<T>::Item
+		{
+			Priority priority;
+		};
 
 	protected:
 
 		T * const      _idle;
-		Double_list<T> _items;
+		T *            _current;
+		Double_list<T> _items[Priority::MAX+1];
 
 	public:
 
 		/**
 		 * Constructor
 		 */
-		Scheduler(T * const idle) : _idle(idle) { }
+		Scheduler(T * const idle) : _idle(idle), _current(0) { }
 
 		/**
 		 * Get currently scheduled item
 		 */
-		T * head() const
+		T * head()
 		{
-			T * const i = _items.head();
-			if (i) { return i; }
+			for (int i = Priority::MAX; i >= 0 ; i--) {
+				_current = _items[i].head();
+				if (_current) return _current;
+			}
 			return _idle;
 		}
 
 		/**
 		 * End turn of currently scheduled item
 		 */
-		void yield() { _items.head_to_tail(); }
+		void yield()
+		{
+			if (!_current) return;
+			_items[_current->priority].head_to_tail();
+		}
 
 		/**
 		 * Include 'i' in scheduling
@@ -190,13 +201,13 @@ class Kernel::Scheduler
 		void insert(T * const i)
 		{
 			assert(i != _idle);
-			_items.insert_tail(i);
+			_items[i->priority].insert_tail(i);
 		}
 
 		/**
 		 * Exclude 'i' from scheduling
 		 */
-		void remove(T * const i) { _items.remove(i); }
+		void remove(T * const i) { _items[i->priority].remove(i); }
 };
 
 #endif /* _KERNEL__SCHEDULER_H_ */

base-hw/src/core/kernel/thread.cc

@@ -75,3 +75,13 @@ Kernel::Thread::prepare_to_start(void * const        ip,
 		      this->pd_id(), pd_label(), id(), label());
 	}
 }
+
+
+Kernel::Thread::Thread(Platform_thread * const platform_thread)
+: _platform_thread(platform_thread), _state(AWAIT_START),
+  _pager(0), _pd_id(0), _phys_utcb(0), _virt_utcb(0),
+  _signal_receiver(0)
+{
+	priority = _platform_thread ? _platform_thread->priority()
+	                            : Kernel::Priority::MAX;
+}

base-hw/src/core/kernel/thread.h

@@ -309,12 +309,7 @@ class Kernel::Thread
 		 *
 		 * \param platform_thread  userland backend of execution context
 		 */
-		Thread(Platform_thread * const platform_thread)
-		:
-			_platform_thread(platform_thread), _state(AWAIT_START),
-			_pager(0), _pd_id(0), _phys_utcb(0), _virt_utcb(0),
-			_signal_receiver(0)
-		{ }
+		Thread(Platform_thread * const platform_thread);
 
 		/**
 		 * Return wether the thread is a core thread

base-hw/src/core/platform_thread.cc

@@ -77,7 +77,9 @@ Platform_thread::Platform_thread(const char * name,
                                  size_t const stack_size, unsigned const pd_id)
 :
 	_thread_base(thread_base), _stack_size(stack_size),
-	_pd_id(pd_id), _rm_client(0), _virt_utcb(0), _main_thread(0)
+	_pd_id(pd_id), _rm_client(0), _virt_utcb(0),
+	_priority(Kernel::Priority::MAX),
+	_main_thread(0)
 {
 	strncpy(_name, name, NAME_MAX_LEN);
 
@@ -100,7 +102,9 @@ Platform_thread::Platform_thread(const char * name, unsigned int priority,
                                  addr_t utcb)
 :
 	_thread_base(0), _stack_size(0), _pd_id(0), _rm_client(0),
-	_virt_utcb((Native_utcb *)utcb), _main_thread(0)
+	_virt_utcb((Native_utcb *)utcb),
+	_priority(Cpu_session::scale_priority(Kernel::Priority::MAX, priority)),
+	_main_thread(0)
 {
 	strncpy(_name, name, NAME_MAX_LEN);