From 9b38b2cdebc2bde00e85fc4ed8ed7bef400f6c8c Mon Sep 17 00:00:00 2001
From: Nathan Harmata <nharmata@google.com>
Date: Thu, 27 Aug 2015 16:11:07 +0000
Subject: Be resilient to a non-decreasing clock in
 BlazeRuntime#recordLastExecutionTime. Also add @Nullable annotations as
 appropriate.

Fixes #394.

--
MOS_MIGRATED_REVID=101685096
---
 .../com/google/devtools/build/lib/buildtool/SkyframeBuilder.java    | 4 +++-
 .../java/com/google/devtools/build/lib/runtime/BlazeRuntime.java    | 6 +++++-
 .../google/devtools/build/lib/skyframe/FilesystemValueChecker.java  | 5 +++--
 .../com/google/devtools/build/lib/skyframe/SkyframeExecutor.java    | 2 +-
 4 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/src/main/java/com/google/devtools/build/lib/buildtool/SkyframeBuilder.java b/src/main/java/com/google/devtools/build/lib/buildtool/SkyframeBuilder.java
index 0ab5e8059c..fd91a9358b 100644
--- a/src/main/java/com/google/devtools/build/lib/buildtool/SkyframeBuilder.java
+++ b/src/main/java/com/google/devtools/build/lib/buildtool/SkyframeBuilder.java
@@ -66,6 +66,8 @@ import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicBoolean;
 
+import javax.annotation.Nullable;
+
 /**
  * A {@link Builder} implementation driven by Skyframe.
  */
@@ -103,7 +105,7 @@ public class SkyframeBuilder implements Builder {
       Executor executor,
       Set<ConfiguredTarget> builtTargets,
       boolean explain,
-      Range<Long> lastExecutionTimeRange)
+      @Nullable Range<Long> lastExecutionTimeRange)
       throws BuildFailedException, AbruptExitException, TestExecException, InterruptedException {
     skyframeExecutor.prepareExecution(checkOutputFiles, lastExecutionTimeRange);
     skyframeExecutor.setFileCache(fileCache);
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/BlazeRuntime.java b/src/main/java/com/google/devtools/build/lib/runtime/BlazeRuntime.java
index 3a4f3e1d90..ddd3cb1585 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/BlazeRuntime.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/BlazeRuntime.java
@@ -168,6 +168,7 @@ public final class BlazeRuntime {
   private Path workingDirectory;
   private long commandStartTime;
 
+  @Nullable
   private Range<Long> lastExecutionStartFinish = null;
 
   private final SkyframeExecutor skyframeExecutor;
@@ -408,7 +409,10 @@ public final class BlazeRuntime {
   }
 
   public void recordLastExecutionTime() {
-    lastExecutionStartFinish = Range.closed(commandStartTime, clock.currentTimeMillis());
+    long currentTimeMillis = clock.currentTimeMillis();
+    lastExecutionStartFinish = currentTimeMillis >= commandStartTime
+        ? Range.closed(commandStartTime, currentTimeMillis)
+        : null;
   }
 
   /**
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/FilesystemValueChecker.java b/src/main/java/com/google/devtools/build/lib/skyframe/FilesystemValueChecker.java
index 9e00da1ce4..3c414d8126 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/FilesystemValueChecker.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/FilesystemValueChecker.java
@@ -67,20 +67,21 @@ class FilesystemValueChecker {
       SkyFunctionName.functionIs(SkyFunctions.ACTION_EXECUTION);
 
   private final TimestampGranularityMonitor tsgm;
+  @Nullable
   private final Range<Long> lastExecutionTimeRange;
   private final Supplier<Map<SkyKey, SkyValue>> valuesSupplier;
   private AtomicInteger modifiedOutputFilesCounter = new AtomicInteger(0);
   private AtomicInteger modifiedOutputFilesIntraBuildCounter = new AtomicInteger(0);
 
   FilesystemValueChecker(Supplier<Map<SkyKey, SkyValue>> valuesSupplier,
-      TimestampGranularityMonitor tsgm, Range<Long> lastExecutionTimeRange) {
+      TimestampGranularityMonitor tsgm, @Nullable Range<Long> lastExecutionTimeRange) {
     this.valuesSupplier = valuesSupplier;
     this.tsgm = tsgm;
     this.lastExecutionTimeRange = lastExecutionTimeRange;
   }
 
   FilesystemValueChecker(final MemoizingEvaluator evaluator, TimestampGranularityMonitor tsgm,
-      Range<Long> lastExecutionTimeRange) {
+      @Nullable Range<Long> lastExecutionTimeRange) {
     this.tsgm = tsgm;
     this.lastExecutionTimeRange = lastExecutionTimeRange;
 
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java b/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java
index c6b5a22f82..907a89a939 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java
@@ -1634,7 +1634,7 @@ public abstract class SkyframeExecutor implements WalkableGraphFactory {
   }
 
   public void prepareExecution(boolean checkOutputFiles,
-      Range<Long> lastExecutionTimeRange) throws AbruptExitException,
+      @Nullable Range<Long> lastExecutionTimeRange) throws AbruptExitException,
       InterruptedException {
     maybeInjectEmbeddedArtifacts();
 
-- 
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