lucene at mikemccandless
Nov 27, 2009, 10:29 AM
Post #3 of 3
(270 views)
Permalink
|
True... I'll make that change too.
Mike
On Fri, Nov 27, 2009 at 12:56 PM, Jason Rutherglen
<jason.rutherglen [at] gmail> wrote:
> If syncing on directory is not important, then sizeInBytes can be an AtomicLong?
>
> On Fri, Nov 27, 2009 at 8:37 AM, Michael McCandless
> <lucene [at] mikemccandless> wrote:
>> RAMFile has this method:
>>
>> final synchronized byte[] addBuffer(int size) {
>> byte[] buffer = newBuffer(size);
>> if (directory!=null)
>> synchronized (directory) { // Ensure addition of
>> buffer and adjustment to directory size are atomic wrt directory
>> buffers.add(buffer);
>> directory.sizeInBytes += size;
>> sizeInBytes += size;
>> }
>> else
>> buffers.add(buffer);
>> return buffer;
>> }
>>
>> But in working on LUCENE-2095, I'm seeing a deadlock, because that
>> method first syncs on RAMFile and then tries to sync on directory,
>> while the MockRAMDirectory.crash method, and I think maybe other
>> places, do the reverse. I remember also hitting a different deadlock
>> from this in the past, and working around it.
>>
>> I'd like to break the deadlock by changing RAMFile to this:
>>
>> final byte[] addBuffer(int size) {
>> byte[] buffer = newBuffer(size);
>> synchronized(this) {
>> buffers.add(buffer);
>> sizeInBytes += size;
>> }
>>
>> if (directory != null) {
>> synchronized (directory) {
>> directory.sizeInBytes += size;
>> }
>> }
>> return buffer;
>> }
>>
>> But, then, the addition of the buffer and the change of sizeInBytes is
>> no longer atomic wrt the directory (as the comment says).
>>
>> So my question is... is this change OK? Why is/was it so crucial that
>> the sizeInBytes & RAMFile's buffers really change only atomically?
>> Ie, it seems harmless if RAMDirectory.sizeInBytes() might not include
>> a buffer that's in the process of being added...?
>>
>> (I do see TestRAMDirectory.testRAMDirectorySize requires this
>> atomicity, but, I can fix the test to only check the size in the
>> end...).
>>
>> Mike
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: java-dev-unsubscribe [at] lucene
>> For additional commands, e-mail: java-dev-help [at] lucene
>>
>>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: java-dev-unsubscribe [at] lucene
> For additional commands, e-mail: java-dev-help [at] lucene
>
>
---------------------------------------------------------------------
To unsubscribe, e-mail: java-dev-unsubscribe [at] lucene
For additional commands, e-mail: java-dev-help [at] lucene
|
