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8267042: bug in monitor locking/unlocking on ARM32 C1 due to uninitia…
…lized BasicObjectLock::_displaced_header

Co-authored-by: Chris Cole <chris@sageembedded.com>
Reviewed-by: dsamersoff
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Boris Ulasevich and chrishcole committed Jun 18, 2021
1 parent 5ae9a12 commit 8f2456e5b058a88730ec383d88634737849afdfb
Showing 3 changed files with 176 additions and 4 deletions.
@@ -234,8 +234,9 @@ int C1_MacroAssembler::lock_object(Register hdr, Register obj,
// -2- test (hdr - SP) if the low two bits are 0
sub(tmp2, hdr, SP, eq);
movs(tmp2, AsmOperand(tmp2, lsr, exact_log2(os::vm_page_size())), eq);
// If 'eq' then OK for recursive fast locking: store 0 into a lock record.
str(tmp2, Address(disp_hdr, mark_offset), eq);
// If still 'eq' then recursive locking OK
// set to zero if recursive lock, set to non zero otherwise (see discussion in JDK-8267042)
str(tmp2, Address(disp_hdr, mark_offset));
b(fast_lock_done, eq);
// else need slow case
b(slow_case);
@@ -1180,8 +1180,9 @@ nmethod* SharedRuntime::generate_native_wrapper(MacroAssembler* masm,
// -2- test (hdr - SP) if the low two bits are 0
__ sub(Rtemp, mark, SP, eq);
__ movs(Rtemp, AsmOperand(Rtemp, lsr, exact_log2(os::vm_page_size())), eq);
// If still 'eq' then recursive locking OK: set displaced header to 0
__ str(Rtemp, Address(disp_hdr, BasicLock::displaced_header_offset_in_bytes()), eq);
// If still 'eq' then recursive locking OK
// set to zero if recursive lock, set to non zero otherwise (see discussion in JDK-8267042)
__ str(Rtemp, Address(disp_hdr, BasicLock::displaced_header_offset_in_bytes()));
__ b(lock_done, eq);
__ b(slow_lock);

@@ -0,0 +1,170 @@
/*
* Copyright (c) 2021, 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 compiler.c1;

import java.io.IOException;
import java.io.InterruptedIOException;

/*
* @test
* @author Chris Cole
* @bug 8267042
* @summary missing displaced_header initialization causes hangup
* @run main/othervm -XX:+TieredCompilation -XX:TieredStopAtLevel=1
* -XX:-BackgroundCompilation -XX:CompileThreshold=1
* -XX:CompileOnly=compiler.c1.Test8267042::write
* compiler.c1.Test8267042
*/
public class Test8267042 {

private static int DATA_SIZE = 4;

private char buffer;
private boolean empty = true;

public static void main(String[] args) {
Test8267042 test = new Test8267042();
test.run();
}

private void run() {
System.out.println("Starting test");

Thread writeThread = new Thread(new Runnable() {
@Override
public void run() {
char data[] = new char[DATA_SIZE];
try {
write(data, 0, data.length);
} catch (IOException e) {
e.printStackTrace();
}
}
});
writeThread.setDaemon(true);
writeThread.start();

Thread readThread = new Thread(new Runnable() {
@Override
public void run() {
try {
for (int i = 0; i < DATA_SIZE; i++) {
read();
}
} catch (IOException e) {
e.printStackTrace();
}
}
});
readThread.setDaemon(true);
readThread.start();

try {
writeThread.join(5000);
if (writeThread.isAlive()) {
throw new InternalError("write thread deadlocked");
}
readThread.join(5000);
if (readThread.isAlive()) {
throw new InternalError("read thread deadlocked");
}
} catch (InterruptedException e) {
throw new InternalError("unexpected InterrruptedException while waiting to join threads", e);
}
System.out.println("Test passed");
}

synchronized void write(char data[], int offset, int length) throws IOException {
while (--length >= 0) {
getZeroOnStack(offset);
write(data[offset++]);
}
}

synchronized void write(int c) throws IOException {
while (!empty) {
try {
wait(1000);
} catch (InterruptedException e) {
throw new InterruptedIOException();
}
}
buffer = (char) c;
empty = false;
notifyAll();
}

public synchronized int read() throws IOException {
while (empty) {
try {
System.out.println("read() before wait");
wait(1000);
System.out.println("read() after wait");
} catch (InterruptedException e) {
throw new InterruptedIOException();
}
}
int value = buffer;
empty = true;
notifyAll();
return value;
}

private void getZeroOnStack(int offset) {
int l1;
int l2;
int l3;
int l4;
int l5;
int l6;
int l7;
int l8;
int l9;
int l10;
int l11;
int l12;
int l13;
int l14;
int l15;
int l16;

l1 = 0;
l2 = 0;
l3 = 0;
l4 = 0;
l5 = 0;
l6 = 0;
l7 = 0;
l8 = 0;
l9 = 0;
l10 = 0;
l11 = 0;
l12 = 0;
l13 = 0;
l14 = 0;
l15 = 0;
l16 = 0;
}
}

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