linux-kernel - [PATCH 02/50] mars: add new file drivers/block/mars/lamport.c

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Message-Id: <1404251250-22992-3-git-send-email-tst@schoebel-theuer.de>
Date:	Tue,  1 Jul 2014 23:46:42 +0200
From:	Thomas Schoebel-Theuer <tst@...oebel-theuer.de>
To:	linux-kernel@...r.kernel.org
Subject: [PATCH 02/50] mars: add new file drivers/block/mars/lamport.c

Signed-off-by: Thomas Schoebel-Theuer <tst@...oebel-theuer.de>
---
 drivers/block/mars/lamport.c | 48 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 drivers/block/mars/lamport.c

diff --git a/drivers/block/mars/lamport.c b/drivers/block/mars/lamport.c
new file mode 100644
index 0000000..67484c5
--- /dev/null
+++ b/drivers/block/mars/lamport.c
@@ -0,0 +1,48 @@
+/*  (c) 2010 Thomas Schoebel-Theuer / 1&1 Internet AG */
+
+#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);
+}
+EXPORT_SYMBOL_GPL(get_lamport);
+
+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);
+}
+EXPORT_SYMBOL_GPL(set_lamport);
-- 
2.0.0

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