From 8a256a9f6f277be1a2fe266b4578e7e0b403ee92 Mon Sep 17 00:00:00 2001
From: "Bjoern B. Brandenburg" <bbb@cs.unc.edu>
Date: Tue, 19 Feb 2008 13:13:57 -0500
Subject: litmus: synchronous task release API

This adds the internals for two new systems calls:
	- sys_wait_for_ts_release()
	- sys_release_ts()

The first system call  suspends a task until the task systems is
released with the second system call.
---
 include/litmus/rt_param.h |  1 +
 litmus/sync.c             | 85 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 86 insertions(+)
 create mode 100644 litmus/sync.c

diff --git a/include/litmus/rt_param.h b/include/litmus/rt_param.h
index 9fb5b19b78..1f94e45578 100644
--- a/include/litmus/rt_param.h
+++ b/include/litmus/rt_param.h
@@ -30,6 +30,7 @@ typedef enum {
 struct rt_task {
 	lt_t 		exec_cost;
 	lt_t 		period;
+	lt_t		phase;
 	unsigned int  	cpu;
 	task_class_t  	cls;
 };
diff --git a/litmus/sync.c b/litmus/sync.c
new file mode 100644
index 0000000000..fccde19236
--- /dev/null
+++ b/litmus/sync.c
@@ -0,0 +1,85 @@
+/* litmus/sync.c - Support for synchronous and asynchronous task system releases.
+ *
+ *
+ */
+
+#include <asm/atomic.h>
+#include <asm/uaccess.h>
+#include <linux/spinlock.h>
+#include <linux/list.h>
+#include <linux/sched.h>
+#include <linux/completion.h>
+
+#include <litmus/litmus.h>
+#include <litmus/jobs.h>
+
+static DECLARE_COMPLETION(ts_release);
+
+static long do_wait_for_ts_release(void)
+{
+	long ret = 0;
+
+	/* If the interruption races with a release, the completion object
+	 * may have a non-zero counter. To avoid this problem, this should
+	 * be replaced by wait_for_completion().
+	 *
+	 * For debugging purposes, this is interruptible for now.
+	 */
+	ret = wait_for_completion_interruptible(&ts_release);
+
+	return ret;
+}
+
+
+static long do_release_ts(lt_t start)
+{
+	long ret = 0;
+	int  task_count = 0;
+	long flags;
+	struct list_head	*pos;
+	struct task_struct 	*t;
+
+
+	spin_lock_irqsave(&ts_release.wait.lock, flags);
+
+	list_for_each(pos, &ts_release.wait.task_list) {
+		t = (struct task_struct*) list_entry(pos,
+						     struct __wait_queue,
+						     task_list)->private;
+		task_count++;
+		release_at(t, start + t->rt_param.task_params.phase);
+	}
+
+	spin_unlock_irqrestore(&ts_release.wait.lock, flags);
+
+	complete_n(&ts_release, task_count);
+
+	return ret;
+}
+
+
+asmlinkage long sys_wait_for_ts_release(void)
+{
+	long ret = -EPERM;
+	struct task_struct *t = current;
+
+	if (is_realtime(t))
+		ret = do_wait_for_ts_release();
+
+	return ret;
+}
+
+
+asmlinkage long sys_release_ts(lt_t __user *__delay)
+{
+	long ret;
+	lt_t delay;
+
+	/* FIXME: check capabilities... */
+
+	ret = copy_from_user(&delay, __delay, sizeof(lt_t));
+	if (ret == 0)
+		ret = do_release_ts(sched_clock() + delay);
+
+	return ret;
+}
-- 
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