From 064af42167bf4fc9aaea2702d80ce08074b889c0 Mon Sep 17 00:00:00 2001
From: Ben Pfaff <blp@nicira.com>
Date: Wed, 8 Jul 2009 13:19:16 -0700
Subject: Import from old repository commit
 61ef2b42a9c4ba8e1600f15bb0236765edc2ad45.

---
 .../linux-2.6/compat-2.6/include/linux/timer.h     | 96 ++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 datapath/linux-2.6/compat-2.6/include/linux/timer.h

(limited to 'datapath/linux-2.6/compat-2.6/include/linux/timer.h')

diff --git a/datapath/linux-2.6/compat-2.6/include/linux/timer.h b/datapath/linux-2.6/compat-2.6/include/linux/timer.h
new file mode 100644
index 00000000..6c3a9b0f
--- /dev/null
+++ b/datapath/linux-2.6/compat-2.6/include/linux/timer.h
@@ -0,0 +1,96 @@
+#ifndef __LINUX_TIMER_WRAPPER_H
+#define __LINUX_TIMER_WRAPPER_H 1
+
+#include_next <linux/timer.h>
+
+#include <linux/version.h>
+
+#ifndef RHEL_RELEASE_VERSION
+#define RHEL_RELEASE_VERSION(X,Y) ( 0 )
+#endif
+#if ((LINUX_VERSION_CODE < KERNEL_VERSION(2,6,20)) && \
+     (!defined(RHEL_RELEASE_CODE) || \
+      (RHEL_RELEASE_CODE < RHEL_RELEASE_VERSION(5,1))))
+
+extern unsigned long volatile jiffies;
+
+/**
+ * __round_jiffies - function to round jiffies to a full second
+ * @j: the time in (absolute) jiffies that should be rounded
+ * @cpu: the processor number on which the timeout will happen
+ *
+ * __round_jiffies() rounds an absolute time in the future (in jiffies)
+ * up or down to (approximately) full seconds. This is useful for timers
+ * for which the exact time they fire does not matter too much, as long as
+ * they fire approximately every X seconds.
+ *
+ * By rounding these timers to whole seconds, all such timers will fire
+ * at the same time, rather than at various times spread out. The goal
+ * of this is to have the CPU wake up less, which saves power.
+ *
+ * The exact rounding is skewed for each processor to avoid all
+ * processors firing at the exact same time, which could lead
+ * to lock contention or spurious cache line bouncing.
+ *
+ * The return value is the rounded version of the @j parameter.
+ */
+static inline unsigned long __round_jiffies(unsigned long j, int cpu)
+{
+	int rem;
+	unsigned long original = j;
+
+	/*
+	 * We don't want all cpus firing their timers at once hitting the
+	 * same lock or cachelines, so we skew each extra cpu with an extra
+	 * 3 jiffies. This 3 jiffies came originally from the mm/ code which
+	 * already did this.
+	 * The skew is done by adding 3*cpunr, then round, then subtract this
+	 * extra offset again.
+	 */
+	j += cpu * 3;
+
+	rem = j % HZ;
+
+	/*
+	 * If the target jiffie is just after a whole second (which can happen
+	 * due to delays of the timer irq, long irq off times etc etc) then
+	 * we should round down to the whole second, not up. Use 1/4th second
+	 * as cutoff for this rounding as an extreme upper bound for this.
+	 */
+	if (rem < HZ/4) /* round down */
+		j = j - rem;
+	else /* round up */
+		j = j - rem + HZ;
+
+	/* now that we have rounded, subtract the extra skew again */
+	j -= cpu * 3;
+
+	if (j <= jiffies) /* rounding ate our timeout entirely; */
+		return original;
+	return j;
+}
+
+
+/**
+ * round_jiffies - function to round jiffies to a full second
+ * @j: the time in (absolute) jiffies that should be rounded
+ *
+ * round_jiffies() rounds an absolute time in the future (in jiffies)
+ * up or down to (approximately) full seconds. This is useful for timers
+ * for which the exact time they fire does not matter too much, as long as
+ * they fire approximately every X seconds.
+ *
+ * By rounding these timers to whole seconds, all such timers will fire
+ * at the same time, rather than at various times spread out. The goal
+ * of this is to have the CPU wake up less, which saves power.
+ *
+ * The return value is the rounded version of the @j parameter.
+ */
+static inline unsigned long round_jiffies(unsigned long j)
+{
+	return __round_jiffies(j, 0);  // FIXME
+}
+
+#endif /* linux kernel < 2.6.20 */
+
+#endif
-- 
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