From 6c56813b5e428967f28f77d27e87e3270e78ca63 Mon Sep 17 00:00:00 2001
From: Peter Lawrey <peter.lawrey@higherfrequencytrading.com>
Date: Mon, 18 May 2015 10:12:34 +0100
Subject: [PATCH] HCOLL-333 Change for read and update, write and upgrade to
 come.

---
 .../chronicle/hash/impl/BigSegmentHeader.java | 61 +++++++++++++++++--
 1 file changed, 57 insertions(+), 4 deletions(-)

diff --git a/src/main/java/net/openhft/chronicle/hash/impl/BigSegmentHeader.java b/src/main/java/net/openhft/chronicle/hash/impl/BigSegmentHeader.java
index e02488138..6261449b8 100644
--- a/src/main/java/net/openhft/chronicle/hash/impl/BigSegmentHeader.java
+++ b/src/main/java/net/openhft/chronicle/hash/impl/BigSegmentHeader.java
@@ -56,8 +56,9 @@ public final class BigSegmentHeader implements SegmentHeader {
 
     static final long DELETED_OFFSET = EXCLUSIVE_LOCK_HOLDER_THREAD_ID_OFFSET + 8L;
 
-    private BigSegmentHeader() {}
-    
+    private BigSegmentHeader() {
+    }
+
     @Override
     public long size(long address) {
         return UNSAFE.getInt(address + SIZE_OFFSET) & UNSIGNED_INT_MASK;
@@ -232,7 +233,16 @@ public final class BigSegmentHeader implements SegmentHeader {
     }
 
     private boolean tryReadLock0(long address, long time, TimeUnit unit) {
-        long end = System.nanoTime() + unit.toNanos(time);
+        long timeInNanos = unit.toNanos(time);
+        if (timeInNanos < 2000000) {
+            return tryReadLockNanos(address, timeInNanos);
+        } else {
+            return tryReadLockMillis(address, (timeInNanos + 900000) / 1000000);
+        }
+    }
+
+    private boolean tryReadLockNanos(long address, long timeInNanos) {
+        long end = System.nanoTime() + timeInNanos;
         do {
             if (tryReadLock(address))
                 return true;
@@ -240,6 +250,23 @@ public final class BigSegmentHeader implements SegmentHeader {
         return false;
     }
 
+    /**
+     * Use a timer which is more insensitive to jumps in time like GCs and context switches.
+     */
+    private boolean tryReadLockMillis(long address, long timeInMillis) {
+        long lastTime = System.currentTimeMillis();
+        do {
+            if (tryReadLock(address))
+                return true;
+            long now = System.currentTimeMillis();
+            if (now != lastTime) {
+                lastTime = now;
+                timeInMillis--;
+            }
+        } while (timeInMillis >= 0);
+        return false;
+    }
+
     @Override
     public boolean tryUpgradeReadToUpdateLock(long address) {
         int countWord = getCountWord(address);
@@ -288,7 +315,16 @@ public final class BigSegmentHeader implements SegmentHeader {
     }
 
     private boolean tryUpdateLock0(long address, long time, TimeUnit unit) {
-        long end = System.nanoTime() + unit.toNanos(time);
+        long timeInNanos = unit.toNanos(time);
+        if (timeInNanos < 2000000) {
+            return tryUpdateLockNanos(address, timeInNanos);
+        } else {
+            return tryUpdateLockMillis(address, (timeInNanos + 900000) / 1000000);
+        }
+    }
+
+    private boolean tryUpdateLockNanos(long address, long timeInNanos) {
+        long end = System.nanoTime() + timeInNanos;
         do {
             if (tryUpdateLock(address))
                 return true;
@@ -296,6 +332,23 @@ public final class BigSegmentHeader implements SegmentHeader {
         return false;
     }
 
+    /**
+     * Use a timer which is more insensitive to jumps in time like GCs and context switches.
+     */
+    private boolean tryUpdateLockMillis(long address, long timeInMillis) {
+        long lastTime = System.currentTimeMillis();
+        do {
+            if (tryUpdateLock(address))
+                return true;
+            long now = System.currentTimeMillis();
+            if (now != lastTime) {
+                lastTime = now;
+                timeInMillis--;
+            }
+        } while (timeInMillis >= 0);
+        return false;
+    }
+
     @Override
     public void writeLock(long address) {
         if (!tryWriteLock(address, 2, TimeUnit.SECONDS)) {