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Fix race condition in ThreadJob.waitForRun #659
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ThreadJob.waitForRun() suffers from a race condition. Between checking
for a blocking job with a conflicting scheduling rule and starting to
wait on the state lock of that blocking job to get notified when the
scheduling rule is released, the blocking job may have already changed
its state and acquired a different scheduling rule, such that no
conflict exists anymore. Since this condition is not reevaluated but
waiting on the lock object is started without a timeout, the blocked job
unnecessarily waits for the initially blocking job to change its state
again, i.e., to finish its execution.

With this change, the scheduling rules of blocking and blocked thread
are checked for conflicts again before starting to wait on the state
lock in the blocked job. This leads to a reevaluation of the block
condition in case the scheduling rule of the blocking job has changed in
between and avoids the job to unnecessarily block until the blocking job
finishes.

Fixes #659.
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HeikoKlare committed Sep 13, 2023
1 parent 418fcfc commit c641bf0
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Showing 3 changed files with 30 additions and 8 deletions.
Original file line number Diff line number Diff line change
Expand Up @@ -141,6 +141,17 @@ public void testIndividualProjectBuilds_ProjectRelaxedRule() throws Exception {
});
}

@Test
public void testIndividualProjectBuilds_WithManyProjects_ProjectRelaxedRule() throws Exception {
int numberOfParallelBuilds = 60;
var longRunningProjects = createMultipleTestProjects(numberOfParallelBuilds, BuildDurationType.LONG_RUNNING,
RuleType.CURRENT_PROJECT_RELAXED);
executeIndividualFullProjectBuilds(numberOfParallelBuilds, () -> {
assertBuildsToStart(getAllProjects());
assertMinimumNumberOfSimultaneousBuilds(longRunningProjects.size());
});
}

@Test
public void testWorkspaceBuild_NoConflictRule() throws Exception {
int numberOfParallelBuilds = 3;
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2 changes: 1 addition & 1 deletion runtime/bundles/org.eclipse.core.jobs/META-INF/MANIFEST.MF
Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@ Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: %pluginName
Bundle-SymbolicName: org.eclipse.core.jobs; singleton:=true
Bundle-Version: 3.15.0.qualifier
Bundle-Version: 3.15.100.qualifier
Bundle-Vendor: %providerName
Bundle-Localization: plugin
Export-Package: org.eclipse.core.internal.jobs;x-internal:=true,
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Original file line number Diff line number Diff line change
Expand Up @@ -15,8 +15,14 @@

import java.util.List;
import org.eclipse.core.internal.runtime.RuntimeLog;
import org.eclipse.core.runtime.*;
import org.eclipse.core.runtime.jobs.*;
import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.OperationCanceledException;
import org.eclipse.core.runtime.Status;
import org.eclipse.core.runtime.jobs.ISchedulingRule;
import org.eclipse.core.runtime.jobs.Job;
import org.eclipse.core.runtime.jobs.LockListener;

/**
* Captures the implicit job state for a given thread.
Expand Down Expand Up @@ -317,11 +323,16 @@ private static ThreadJob waitForRun(final ThreadJob threadJob, IProgressMonitor
// The actual exit conditions are listed above at the beginning of
// this while loop
int state = blockingJob.getState();
//ensure we don't wait forever if the blocker is waiting, because it might have yielded to me
if (state == Job.RUNNING && canBlock) {
blockingJob.jobStateLock.wait();
} else if (state != Job.NONE) {
blockingJob.jobStateLock.wait(250);
// Check that blockingJob has not acquired a different, non-conflicting
// scheduling rule since checking for conflicts by JobManager
if (state != Job.NONE && blockingJob.getRule().isConflicting(threadJob.getRule())) {
// ensure we don't wait forever if the blocker is waiting, because it might have
// yielded to me
if (state == Job.RUNNING && canBlock) {
blockingJob.jobStateLock.wait();
} else {
blockingJob.jobStateLock.wait(250);
}
}
} catch (InterruptedException e) {
// This thread may be interrupted via two common scenarios. 1) If
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