RFR: JDK-8241883: (zipfs) SeekableByteChannel:close followed by SeekableByteChannel:close will throw an NPE

[Lance Andersen]

> On Apr 8, 2020, at 4:26 PM, Alan Bateman <Alan.Bateman at oracle.com> wrote:
> 
> 
> 
> On 08/04/2020 20:36, Lance Andersen wrote:
>> :
>> 
>> ——————————
>> $ hg diff
>> diff -r f4c174bf0276 src/jdk.zipfs/share/classes/jdk/nio/zipfs/ZipFileSystem.java
>> --- a/src/jdk.zipfs/share/classes/jdk/nio/zipfs/ZipFileSystem.java      Tue Apr 07 09:03:05 2020 -0400
>> +++ b/src/jdk.zipfs/share/classes/jdk/nio/zipfs/ZipFileSystem.java      Wed Apr 08 11:07:30 2020 -0400
>> @@ -876,6 +876,7 @@
>>      // channel is closed
>>      private class EntryOutputChannel extends ByteArrayChannel {
>>          final Entry e;
>> +        final ReadWriteLock rwlock = new ReentrantReadWriteLock();
>>  
>>          EntryOutputChannel(Entry e) {
>>              super(e.size > 0? (int)e.size : 8192, false);
>> @@ -892,11 +893,24 @@
>>  
>>          @Override
>>          public void close() throws IOException {
>> -            // will update the entry
>> -            try (OutputStream os = getOutputStream(e)) {
>> -                os.write(toByteArray());
>> +            beginWrite();
>> +            try {
>> +                if(!isOpen())
>> +                    return;
>> +                // will update the entry
>> +                try (OutputStream os = getOutputStream(e)) {
>> +                    os.write(toByteArray());
>> +                }
>> +                super.close();
>> +            } finally {
>> +                endWrite();
>>              }
>> -            super.close();
>> +        }
>> +        private final void beginWrite() {
>> +            rwlock.writeLock().lock();
>> +        }
>> +        private final void endWrite() {
>> +            rwlock.writeLock().unlock();
>>          }
>> 
> That is the equivalent of close synchronizing on any object. Are there any code paths use the readLock?

In the case of the close method above, ByteArrayChannel::toByteArray uses a readLock  ByteArrayChannel::close uses a writeLock

Best
Lance
> 
> -Alan

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 <http://oracle.com/us/design/oracle-email-sig-198324.gif>Lance Andersen| Principal Member of Technical Staff | +1.781.442.2037
Oracle Java Engineering 
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Lance.Andersen at oracle.com <mailto:Lance.Andersen at oracle.com>



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