From 001b0695092a800d68a4c9078c051f4fd2ff0d3d Mon Sep 17 00:00:00 2001
From: Norman Feske <norman.feske@genode-labs.com>
Date: Mon, 16 Mar 2015 16:44:11 +0100
Subject: [PATCH] Simplify base/semaphore.h, fix #1453

---
 repos/base/include/base/semaphore.h   | 110 ++++----------------------
 repos/os/include/os/timed_semaphore.h |   2 +-
 2 files changed, 17 insertions(+), 95 deletions(-)

diff --git a/repos/base/include/base/semaphore.h b/repos/base/include/base/semaphore.h
index 7adeb09435..f0908f0b01 100644
--- a/repos/base/include/base/semaphore.h
+++ b/repos/base/include/base/semaphore.h
@@ -16,96 +16,27 @@
 #define _INCLUDE__BASE__SEMAPHORE_H_
 
 #include <base/lock.h>
-#include <util/list.h>
 #include <util/fifo.h>
 
-namespace Genode {
-
-	struct Semaphore_queue;
-	class Fifo_semaphore_queue;
-
-	template <typename, typename> class Semaphore_template;
-}
+namespace Genode { class Semaphore; }
 
 
-/**
- * Semaphore queue interface
- */
-struct Genode::Semaphore_queue
-{
-	/**
-	 * Semaphore-queue elements
-	 *
-	 * A queue element represents a thread blocking on the
-	 * semaphore.
-	 */
-	class Element : Lock
-	{
-		public:
-
-			/**
-			 * Constructor
-			 */
-			Element() : Lock(LOCKED) { }
-
-			void block()   { lock();   }
-			void wake_up() { unlock(); }
-	};
-
-	/**
-	 * Add new queue member that is going to block
-	 */
-	void enqueue(Element *e);
-
-	/**
-	 * Dequeue queue member to wake up next
-	 */
-	Element *dequeue();
-};
-
-
-/**
- * First-in-first-out variant of the semaphore-queue interface
- */
-class Genode::Fifo_semaphore_queue : public Semaphore_queue
-{
-	public:
-
-		class Element : public Semaphore_queue::Element,
-		                public Fifo<Element>::Element { };
-
-	private:
-
-		Fifo<Element> _fifo;
-
-	public:
-
-		void enqueue(Element *e) { _fifo.enqueue(e); }
-
-		Element *dequeue()  { return _fifo.dequeue(); }
-};
-
-
-/**
- * Semaphore base template
- *
- * \param QT  semaphore wait queue type implementing the
- *            'Semaphore_queue' interface
- * \param QTE wait-queue element type implementing the
- *            'Semaphore_queue::Element' interface
- *
- * The queuing policy is defined via the QT and QTE types.
- * This way, the platform-specific semaphore-queueing policies
- * such as priority-sorted queueing can be easily supported.
- */
-template <typename QT, typename QTE>
-class Genode::Semaphore_template
+class Genode::Semaphore
 {
 	protected:
 
 		int  _cnt;
 		Lock _meta_lock;
-		QT   _queue;
+
+		struct Element : Fifo<Element>::Element
+		{
+			Lock lock { Lock::LOCKED };
+
+			void block()   { lock.lock();   }
+			void wake_up() { lock.unlock(); }
+		};
+
+		Fifo<Element> _queue;
 
 	public:
 
@@ -114,9 +45,9 @@ class Genode::Semaphore_template
 		 *
 		 * \param n  initial counter value of the semphore
 		 */
-		Semaphore_template(int n = 0) : _cnt(n) { }
+		Semaphore(int n = 0) : _cnt(n) { }
 
-		~Semaphore_template()
+		~Semaphore()
 		{
 			/* synchronize destruction with unfinished 'up()' */
 			try { _meta_lock.lock(); } catch (...) { }
@@ -133,7 +64,7 @@ class Genode::Semaphore_template
 			 * Remove element from queue and wake up the corresponding
 			 * blocking thread
 			 */
-			Semaphore_queue::Element * element = _queue.dequeue();
+			Element * element = _queue.dequeue();
 			if (element)
 				element->wake_up();
 		}
@@ -148,7 +79,7 @@ class Genode::Semaphore_template
 				 * Create semaphore queue element representing the thread
 				 * in the wait queue.
 				 */
-				QTE queue_element;
+				Element queue_element;
 				_queue.enqueue(&queue_element);
 				_meta_lock.unlock();
 
@@ -170,13 +101,4 @@ class Genode::Semaphore_template
 		int cnt() { return _cnt; }
 };
 
-
-namespace Genode {
-
-	/**
-	 * Semaphore with default behaviour
-	 */
-	typedef Semaphore_template<Fifo_semaphore_queue, Fifo_semaphore_queue::Element> Semaphore;
-}
-
 #endif /* _INCLUDE__BASE__SEMAPHORE_H_ */
diff --git a/repos/os/include/os/timed_semaphore.h b/repos/os/include/os/timed_semaphore.h
index b46cd7ce7f..b01b297c77 100644
--- a/repos/os/include/os/timed_semaphore.h
+++ b/repos/os/include/os/timed_semaphore.h
@@ -82,7 +82,7 @@ class Genode::Timed_semaphore : public Semaphore
 {
 	private:
 
-		typedef Fifo_semaphore_queue::Element Element;
+		typedef Semaphore::Element Element;
 
 		/**
 		 * Aborts blocking on the semaphore, raised when a timeout occured.