[RFC 01/31] mars: add new module lamport

[Thomas Schoebel-Theuer]

Signed-off-by: Thomas Schoebel-Theuer <tst@xxxxxxxxxxxxxxxxxx>
---
 drivers/staging/mars/lamport.c | 61 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/brick/lamport.h  | 26 ++++++++++++++++++
 2 files changed, 87 insertions(+)
 create mode 100644 drivers/staging/mars/lamport.c
 create mode 100644 include/linux/brick/lamport.h

diff --git a/drivers/staging/mars/lamport.c b/drivers/staging/mars/lamport.c
new file mode 100644
index 0000000..373093f
--- /dev/null
+++ b/drivers/staging/mars/lamport.c
@@ -0,0 +1,61 @@
+/*
+ * MARS Long Distance Replication Software
+ *
+ * Copyright (C) 2010-2014 Thomas Schoebel-Theuer
+ * Copyright (C) 2011-2014 1&1 Internet AG
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/semaphore.h>
+
+#include <linux/brick/lamport.h>
+
+/*  TODO: replace with spinlock if possible (first check) */
+struct semaphore lamport_sem = __SEMAPHORE_INITIALIZER(lamport_sem, 1);
+struct timespec lamport_now = {};
+
+void get_lamport(struct timespec *now)
+{
+	int diff;
+
+	down(&lamport_sem);
+
+	*now = CURRENT_TIME;
+	diff = timespec_compare(now, &lamport_now);
+	if (diff >= 0) {
+		timespec_add_ns(now, 1);
+		memcpy(&lamport_now, now, sizeof(lamport_now));
+		timespec_add_ns(&lamport_now, 1);
+	} else {
+		timespec_add_ns(&lamport_now, 1);
+		memcpy(now, &lamport_now, sizeof(*now));
+	}
+
+	up(&lamport_sem);
+}
+
+void set_lamport(struct timespec *old)
+{
+	int diff;
+
+	down(&lamport_sem);
+
+	diff = timespec_compare(old, &lamport_now);
+	if (diff >= 0) {
+		memcpy(&lamport_now, old, sizeof(lamport_now));
+		timespec_add_ns(&lamport_now, 1);
+	}
+
+	up(&lamport_sem);
+}
diff --git a/include/linux/brick/lamport.h b/include/linux/brick/lamport.h
new file mode 100644
index 0000000..9aac0ce
--- /dev/null
+++ b/include/linux/brick/lamport.h
@@ -0,0 +1,26 @@
+/*
+ * MARS Long Distance Replication Software
+ *
+ * Copyright (C) 2010-2014 Thomas Schoebel-Theuer
+ * Copyright (C) 2011-2014 1&1 Internet AG
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef LAMPORT_H
+#define LAMPORT_H
+
+#include <linux/time.h>
+
+extern void get_lamport(struct timespec *now);
+extern void set_lamport(struct timespec *old);
+
+#endif
-- 
2.6.4

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