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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Issue Comment Edited: (CASSANDRA-734) Table.open has a broken lock in it
Date Mon, 25 Jan 2010 01:17:34 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-734?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12804340#action_12804340
] 

Jonathan Ellis edited comment on CASSANDRA-734 at 1/25/10 1:16 AM:
-------------------------------------------------------------------

> How does a NBHM solve the problem get-and-then-put-but-only-instantiate-the-object-at-all-if-get-is-null?

It doesn't: it solves the problem of doing get() on a thread-unsafe object while remaining
high performance.  I'm saying, we can use Table.open in close to its current form by replacing
the current HashMap w/ a NBHM, and continuing to use a synchronized block for if the get()
is null.

> Not if we do the initTable work, and then later turn it in a NBHM.

True enough, but is that then really simpler than just fixing Table.open?

      was (Author: jbellis):
    > How does a NBHM solve the problem get-and-then-put-but-only-instantiate-the-object-at-all-if-get-is-null?

It doesn't: it solves the problem of doing get() on a thread-unsafe object while remaining
high performance.  I'm saying, we can use Table.open in close to its current form by replacing
the current HashMap w/ a NBHM.

> Not if we do the initTable work, and then later turn it in a NBHM.

True enough, but is that then really simpler than just fixing Table.open?
  
> Table.open has a broken lock in it
> ----------------------------------
>
>                 Key: CASSANDRA-734
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-734
>             Project: Cassandra
>          Issue Type: Bug
>    Affects Versions: 0.5
>            Reporter: Jeff Hodges
>            Assignee: Jeff Hodges
>            Priority: Minor
>             Fix For: 0.6
>
>         Attachments: broken_lock_in_table_open.patch
>
>
> Table.open's lock is used around the Map#put method call but not the #get. This makes
it a source of spurious bugs. The attached patch synchronizes the entire Table.open method
and removes the unused createLock static.

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