From 41b99a6b51615651f18c0c216d3d137ed23602b8 Mon Sep 17 00:00:00 2001
From: Norman Feske <norman.feske@genode-labs.com>
Date: Thu, 7 May 2015 14:22:42 +0200
Subject: [PATCH] sel4: use yielding spinlock for 'Genode::Lock'

---
 .../base-sel4/include/base/cancelable_lock.h  | 56 +++++++++++++++++++
 repos/base-sel4/lib/mk/base-common.inc        |  1 -
 repos/base-sel4/src/base/lock/lock.cc         | 44 +++++++++++++++
 repos/base-sel4/src/base/lock/lock_helper.h   | 26 +++------
 4 files changed, 108 insertions(+), 19 deletions(-)
 create mode 100644 repos/base-sel4/include/base/cancelable_lock.h
 create mode 100644 repos/base-sel4/src/base/lock/lock.cc

diff --git a/repos/base-sel4/include/base/cancelable_lock.h b/repos/base-sel4/include/base/cancelable_lock.h
new file mode 100644
index 0000000000..c684501dab
--- /dev/null
+++ b/repos/base-sel4/include/base/cancelable_lock.h
@@ -0,0 +1,56 @@
+/*
+ * \brief  Basic locking primitive
+ * \author Norman Feske
+ * \date   2006-07-26
+ */
+
+/*
+ * Copyright (C) 2006-2013 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 _INCLUDE__BASE__CANCELABLE_LOCK_H_
+#define _INCLUDE__BASE__CANCELABLE_LOCK_H_
+
+#include <base/lock_guard.h>
+#include <base/blocking.h>
+
+namespace Genode {
+
+	class Cancelable_lock
+	{
+		private:
+
+			int volatile _lock;
+
+		public:
+
+			enum State { LOCKED, UNLOCKED };
+
+			/**
+			 * Constructor
+			 */
+			explicit Cancelable_lock(State initial = UNLOCKED);
+
+			/**
+			 * Try to aquire lock an block while lock is not free
+			 *
+			 * This function may throw a Genode::Blocking_canceled exception.
+			 */
+			void lock();
+
+			/**
+			 * Release lock
+			 */
+			void unlock();
+
+			/**
+			 * Lock guard
+			 */
+			typedef Genode::Lock_guard<Cancelable_lock> Guard;
+	};
+}
+
+#endif /* _INCLUDE__BASE__CANCELABLE_LOCK_H_ */
diff --git a/repos/base-sel4/lib/mk/base-common.inc b/repos/base-sel4/lib/mk/base-common.inc
index 5a71e30220..449ff80647 100644
--- a/repos/base-sel4/lib/mk/base-common.inc
+++ b/repos/base-sel4/lib/mk/base-common.inc
@@ -27,7 +27,6 @@ SRC_CC += thread/thread_bootstrap.cc
 #SRC_CC += env/cap_map.cc
 
 INC_DIR +=  $(REP_DIR)/src/base/lock
-INC_DIR += $(BASE_DIR)/src/base/lock
 INC_DIR += $(BASE_DIR)/src/base/thread
 
 vpath %.cc $(REP_DIR)/src/base
diff --git a/repos/base-sel4/src/base/lock/lock.cc b/repos/base-sel4/src/base/lock/lock.cc
new file mode 100644
index 0000000000..f123f7bd6d
--- /dev/null
+++ b/repos/base-sel4/src/base/lock/lock.cc
@@ -0,0 +1,44 @@
+/*
+ * \brief  Lock implementation
+ * \author Norman Feske
+ * \date   2007-10-15
+ */
+
+/*
+ * Copyright (C) 2007-2013 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.
+ */
+
+/* Genode includes */
+#include <base/cancelable_lock.h>
+#include <cpu/atomic.h>
+#include <cpu/memory_barrier.h>
+
+/* seL4 includes */
+#include <sel4/interfaces/sel4_client.h>
+
+using namespace Genode;
+
+
+Cancelable_lock::Cancelable_lock(Cancelable_lock::State initial)
+: _lock(UNLOCKED)
+{
+	if (initial == LOCKED)
+		lock();
+}
+
+
+void Cancelable_lock::lock()
+{
+	while (!Genode::cmpxchg(&_lock, UNLOCKED, LOCKED))
+		seL4_Yield();
+}
+
+
+void Cancelable_lock::unlock()
+{
+	Genode::memory_barrier();
+	_lock = UNLOCKED;
+}
diff --git a/repos/base-sel4/src/base/lock/lock_helper.h b/repos/base-sel4/src/base/lock/lock_helper.h
index 4d09ef2f81..bc357ea92a 100644
--- a/repos/base-sel4/src/base/lock/lock_helper.h
+++ b/repos/base-sel4/src/base/lock/lock_helper.h
@@ -1,31 +1,21 @@
+
 /*
  * \brief  seL4-specific helper functions for the Lock implementation
  * \author Norman Feske
- * \date   2014-10-14
+ * \date   2015-05-07
+ *
+ * Based on the lock implementation of base-fiasco/src/base/lock/.
  */
 
 /*
- * Copyright (C) 2014 Genode Labs GmbH
+ * Copyright (C) 2015 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.
  */
 
-/* Genode includes */
-#include <base/native_types.h>
-#include <base/thread.h>
+/* seL4 includes */
+#include <sel4/interfaces/sel4_client.h>
 
 
-static inline void thread_yield() { }
-
-
-static inline bool thread_check_stopped_and_restart(Genode::Thread_base *)
-{
-	return false;
-}
-
-
-static inline void thread_switch_to(Genode::Thread_base *thread_base) { }
-
-
-static inline void thread_stop_myself() { }
+static inline void thread_yield() { seL4_Yield(); }