On May 11 2012, at 03:12 , Alan Bateman wrote:
> On 11/05/2012 00:11, Mike Duigou wrote:
>>
>> Hello all;
>>
>> A benign but potentially expensive race condition was discovered in
>> java.util.UUID. The initialization of numberGenerator may cause the creation
>> of a number of SecureRandom instances if multiple threads are attempting to
>> initialize the field at the same time. This can happen because creation of
>> the SecureRandom instances, depending upon system configuration and state,
>> may take a significant amount of time.
>>
>> Using a shared SecureRandom instance for the numberGenerator is an
>> optimization--nothing bad happens as a result of each thread using it's own
>> instance. However, creation of multiple SecureRandom instances, especially
>> during system startup, may be expensive or have high latency if no previous
>> SecureRandom instances have been created.
>>
>> Accordingly, a holder class is used to ensure that only a single
>> SecureRandom instance is created. The holder also serves to defer
>> initialization of numberGenerator until randomUUID() is first called.
>>
>> Webrev:
>>
>> http://cr.openjdk.java.net/~mduigou/7071826/0/webrev/
>>
>> This issue will be proposed for backport to Java 7u6 once integrated into
>> Java 8
>>
> The implementation change looks good to me. For the javadoc change then could
> you link to RFC 4122 on the IEFT site?
Yes.
>
> I don't quite get the test update, it improves the test but I don't see how
> it might demonstrate the race condition.
It doesn't demonstrate the race condition. The test changes are mostly just a
result of reviewing the tests while I planned the changes.
> Minor consistency comment is that the if statements use braces whereas the
> existing code doesn't,
According to javastyle guidelines we're supposed to always use braces. I've not
modified existing cases where braces are not present unless modifying the if
expression.
> also missing space in "if(".
Fixed.
>
> -Alan.
>
