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8282947: JFR: Dump on shutdown live-locks in some conditions
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Reviewed-by: phh
Backport-of: 63eb0b7e8606dd9cd145e92eeeb744ff5b7be569
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Jiří Vaněk authored and Paul Hohensee committed Feb 15, 2023
1 parent c183dc5 commit ec53e00
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Showing 3 changed files with 65 additions and 4 deletions.
7 changes: 5 additions & 2 deletions jdk/src/share/classes/jdk/jfr/internal/ChunksChannel.java
Expand Up @@ -96,10 +96,13 @@ public long transferTo(FileChannel out) throws IOException {
assert current != null;

long rem = current.getSize();

while (rem > 0) {
long n = Math.min(rem, 1024 * 1024);
long w = out.transferFrom(channel, pos, n);
// Prevent endless loop
if (w == 0) {
return out.size();
}
pos += w;
rem -= w;
}
Expand All @@ -111,7 +114,7 @@ public long transferTo(FileChannel out) throws IOException {
current = null;
}
if (!nextChannel()) {
return pos;
return out.size();
}
}
}
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8 changes: 6 additions & 2 deletions jdk/src/share/classes/jdk/jfr/internal/PlatformRecording.java
Expand Up @@ -682,8 +682,12 @@ public void dumpStopped(WriteableUserPath userPath) throws IOException {
synchronized (recorder) {
userPath.doPriviligedIO(() -> {
try (ChunksChannel cc = new ChunksChannel(chunks); FileChannel fc = FileChannel.open(userPath.getReal(), StandardOpenOption.WRITE, StandardOpenOption.APPEND)) {
cc.transferTo(fc);
fc.force(true);
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
if (bytes != 0) {
fc.force(true);
}
}
return null;
});
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54 changes: 54 additions & 0 deletions jdk/test/jdk/jfr/api/recording/dump/TestDumpDevNull.java
@@ -0,0 +1,54 @@
/*
* Copyright (c) 2022, 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.io.File;

import jdk.jfr.Recording;

/**
* @test
* @summary Tests that it's possible to dump to /dev/null without a livelock
* @key jfr
*
* @library /lib /
* @run main/othervm jdk.jfr.api.recording.dump.TestDumpDevNull
*/
public class TestDumpDevNull {

public static void main(String[] args) throws Exception {
try (Recording r1 = new Recording()) {
r1.setDestination(new File("/dev/null").toPath());
r1.start();
// Force a chunk rotation which ensures that jdk.jfr.internal.ChunkChannel
// invokes FileChannel::transferFrom(ReadableByteChannel, position, count) twice.
// FileChannel will return 0 the second time because position exceeds
// FileChannel::size(), which is always 0 for /dev/null
// Without proper handling of return value 0, the ChunkChannel will spin indefinitely.
try (Recording r2 = new Recording()) {
r2.start();
}
}
}
}

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