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8370715: JFR: Races are possible when dumping recordings

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Reviewed-by: egahlin, stuefe
This commit is contained in:
Robert Toyonaga 2025-12-04 13:56:17 +00:00 committed by Thomas Stuefe
parent bcbdf90fce
commit c4ec983da5
2 changed files with 88 additions and 1 deletions
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10
src/jdk.jfr/share/classes/jdk/jfr/internal/PlatformRecording.java
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@ -34,6 +34,7 @@ import static jdk.jfr.internal.LogTag.JFR;
import java.io.IOException;
import java.io.InputStream;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.nio.file.NoSuchFileException;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
@ -744,7 +745,14 @@ public final class PlatformRecording implements AutoCloseable {
}
private void transferChunks(WriteablePath path) throws IOException {
try (ChunksChannel cc = new ChunksChannel(chunks); FileChannel fc = FileChannel.open(path.getReal(), StandardOpenOption.WRITE, StandardOpenOption.APPEND)) {
// Before writing, wipe the file if it already exists.
try (ChunksChannel cc = new ChunksChannel(chunks); FileChannel fc = FileChannel.open(path.getReal(), StandardOpenOption.WRITE, StandardOpenOption.TRUNCATE_EXISTING, StandardOpenOption.CREATE)) {
// Mitigate races against other processes
FileLock l = fc.tryLock();
if (l == null) {
Logger.log(LogTag.JFR, LogLevel.INFO, "Dump operation skipped for recording \"" + name + "\" (" + id + "). File " + path.getRealPathText() + " is locked by other dump operation or activity.");
return;
}
long bytes = cc.transferTo(fc);
Logger.log(LogTag.JFR, LogLevel.INFO, "Transferred " + bytes + " bytes from the disk repository");
// No need to force if no data was transferred, which avoids IOException when device is /dev/null

79
test/jdk/jdk/jfr/api/recording/dump/TestDumpOverwrite.java Normal file
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@ -0,0 +1,79 @@
/*
* Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package jdk.jfr.api.recording.dump;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import jdk.jfr.Recording;
import jdk.jfr.consumer.RecordedEvent;
import jdk.jfr.consumer.RecordingFile;
import jdk.test.lib.Asserts;
import jdk.test.lib.jfr.SimpleEventHelper;
import jdk.test.lib.jfr.Events;
/**
* @test
* @summary Test that multiple dumps to the same file by ongoing recordings do not mangle data.
* @requires vm.flagless
* @requires vm.hasJFR
* @library /test/lib
* @run main/othervm jdk.jfr.api.recording.dump.TestDumpOverwrite
*/
public class TestDumpOverwrite {
private static Path DUMP_PATH = Paths.get(".", "rec_TestDumpOverwrite.jfr");
public static void main(String[] args) throws Exception {
Recording recording1 = new Recording();
Recording recording2 = new Recording();
SimpleEventHelper.enable(recording1, true);
SimpleEventHelper.enable(recording2, true);
recording1.setDestination(DUMP_PATH);
recording2.setDestination(DUMP_PATH);
int actualId = 0;
recording1.start();
SimpleEventHelper.createEvent(actualId++);
recording2.start();
SimpleEventHelper.createEvent(actualId++);
// This is results in the initial write to the dump destination
recording2.stop();
SimpleEventHelper.createEvent(actualId++);
recording2.close();
SimpleEventHelper.createEvent(actualId++);
// This should first wipe the data previously written by recording2.
recording1.stop();
recording1.close();
Asserts.assertTrue(Files.exists(DUMP_PATH), "Recording file does not exist: " + DUMP_PATH);
// Verify events are read in order without duplicates (otherwise chunks may be out of order).
// If the dump file is not being overwritten correctly, we will see event ids: 1, 0, 1, 2, 3.
int expectedId = 0;
for (RecordedEvent event : RecordingFile.readAllEvents(DUMP_PATH)) {
Events.assertField(event, "id").equal(expectedId++);
}
Asserts.assertTrue(expectedId == actualId, "incorrect number of events found");
}
}