eclipse-sailing-analytics/sailing-analytics
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reduced likelihood of deadlocks by copying mark roundings in locked area before pulling any other locks

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This commit is contained in:
Axel Uhl committed 2012-12-18 22:28:55 +01:00
1 parent dfd1bc0df0
commit db57bdc6eb
3 files changed
+42 -34
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java/com.sap.sailing.domain/src/com/sap/sailing/domain/base/Course.java
+2
View File
@@ -78,4 +78,6 @@ public interface Course extends Named {
Iterable<Leg> getLegsAdjacentTo(Mark mark);
Leg getFirstLeg();
}
java/com.sap.sailing.domain/src/com/sap/sailing/domain/base/impl/CourseImpl.java
+5
View File
@@ -204,6 +204,11 @@ public class CourseImpl extends NamedImpl implements Course {
}
}
@Override
public Leg getFirstLeg() {
return legs.get(0);
}
@Override
public List<Leg> getLegs() {
lockForRead();
java/com.sap.sailing.domain/src/com/sap/sailing/domain/tracking/impl/TrackedRaceImpl.java
+35 -34
View File
@@ -82,6 +82,7 @@ import com.sap.sailing.domain.tracking.Wind;
import com.sap.sailing.domain.tracking.WindStore;
import com.sap.sailing.domain.tracking.WindTrack;
import com.sap.sailing.domain.tracking.WindWithConfidence;
import com.sap.sailing.util.impl.ArrayListNavigableSet;
import com.sap.sailing.util.impl.LockUtil;
import com.sap.sailing.util.impl.NamedReentrantReadWriteLock;
import com.sap.sailing.util.impl.SmartFutureCache;
@@ -729,36 +730,38 @@ public abstract class TrackedRaceImpl implements TrackedRace, CourseListener {
@Override
public TrackedLegOfCompetitor getTrackedLeg(Competitor competitor, TimePoint at) {
NavigableSet<MarkPassing> roundings = getMarkPassings(competitor);
lockForRead(roundings);
try {
NavigableSet<MarkPassing> localRoundings = new ArrayListNavigableSet<>(roundings.size(), new TimedComparator());
localRoundings.addAll(roundings);
} finally {
unlockAfterRead(roundings);
}
TrackedLegOfCompetitor result = null;
if (roundings != null) {
TrackedLeg trackedLeg;
// obtain last waypoint before obtaining mark passings monitor because obtaining the last waypoint
// obtains the read lock for the course
final Waypoint lastWaypoint = getRace().getCourse().getLastWaypoint();
lockForRead(roundings);
try {
MarkPassing lastBeforeOrAt = roundings.floor(new DummyMarkPassingWithTimePointOnly(at));
// already finished the race?
if (lastBeforeOrAt != null) {
// and not at or after last mark passing
if (lastWaypoint != lastBeforeOrAt.getWaypoint()) {
trackedLeg = getTrackedLegStartingAt(lastBeforeOrAt.getWaypoint());
} else {
// exactly *at* last mark passing?
if (!roundings.isEmpty() && at.equals(roundings.last().getTimePoint())) {
// exactly at finish line; return last leg
trackedLeg = getTrackedLegFinishingAt(lastBeforeOrAt.getWaypoint());
} else {
// no, then we're after the last mark passing
trackedLeg = null;
}
}
MarkPassing lastBeforeOrAt = roundings.floor(new DummyMarkPassingWithTimePointOnly(at));
// already finished the race?
if (lastBeforeOrAt != null) {
// and not at or after last mark passing
if (lastWaypoint != lastBeforeOrAt.getWaypoint()) {
trackedLeg = getTrackedLegStartingAt(lastBeforeOrAt.getWaypoint());
} else {
// before beginning of race
trackedLeg = null;
// exactly *at* last mark passing?
if (!roundings.isEmpty() && at.equals(roundings.last().getTimePoint())) {
// exactly at finish line; return last leg
trackedLeg = getTrackedLegFinishingAt(lastBeforeOrAt.getWaypoint());
} else {
// no, then we're after the last mark passing
trackedLeg = null;
}
}
} finally {
unlockAfterRead(roundings);
} else {
// before beginning of race
trackedLeg = null;
}
if (trackedLeg != null) {
result = trackedLeg.getTrackedLeg(competitor);
@@ -1193,12 +1196,16 @@ public abstract class TrackedRaceImpl implements TrackedRace, CourseListener {
@Override
public Wind call() {
Wind result;
Leg firstLeg = getRace().getCourse().getLegs().iterator().next();
Position firstLegEnd = getApproximatePosition(firstLeg.getTo(), at);
Position firstLegStart = getApproximatePosition(firstLeg.getFrom(), at);
if (firstLegStart != null && firstLegEnd != null) {
result = new WindImpl(firstLegStart, at, new KnotSpeedWithBearingImpl(1.0,
firstLegEnd.getBearingGreatCircle(firstLegStart)));
Leg firstLeg = getRace().getCourse().getFirstLeg();
if (firstLeg != null) {
Position firstLegEnd = getApproximatePosition(firstLeg.getTo(), at);
Position firstLegStart = getApproximatePosition(firstLeg.getFrom(), at);
if (firstLegStart != null && firstLegEnd != null) {
result = new WindImpl(firstLegStart, at, new KnotSpeedWithBearingImpl(1.0,
firstLegEnd.getBearingGreatCircle(firstLegStart)));
} else {
result = null;
}
} else {
result = null;
}
@@ -1209,12 +1216,6 @@ public abstract class TrackedRaceImpl implements TrackedRace, CourseListener {
}
}
if (newFuture != null) {
// FIXME locking problem: this method is sometimes called by code holding the course's read lock.
// If a writer is waiting for the write lock, further read locks aren't granted due to the "fair" locking policy.
// To finish the future, a read lock on the course needs to be obtained in the getLegs() call. This isn't granted
// until the writer times out and tries again. Moving the future execution into a thread doesn't help because the
// future.get() below will again block until the future has finished which can't happen because the writer cannot
// obtain the write lock, and the new read lock isn't granted.
newFuture.run();
future = newFuture;
}