Cyrus 2.3.12 RC1

[Bron Gondwana]

On Wed, 09 Apr 2008 07:51:50 -0400, "Ken Murchison" <murch at andrew.cmu.edu> said:
> Is there a bug somewhere in the rest of the code that causes this
> problem?

Yeah, folderlimit - another of my patches, but the interface is pretty dangerous.
I haven't found any other paths yet, but a bug elsewhere could cause skiplist
corruption if it did a read while there was a transaction open - risky and bogus
interface.

The specific pattern is:

1) a transaction is started in WRITE mode (file locked EXCLUSIVE)

2) a read is done without a transaction being passed
  2a) file gets re-locked in SHARED mode
  2b) file gets unlocked

3) a different process writes to the end of the file

4) the first process believes it still has a lock, and seeks to the end of its
   transaction offset and writes.

You get a file that might look something like this

 |
 v
ADD           ADD 
COMMIT        COMMIT
         <-   ADD
DELETE        COMMIT
ADD      ->   
COMMIT        COMMIT 
                  |
                  v

So there's junk between the commits that was part of the ADD from the transaction
in item (3) above.

Bron.
-- 
  Bron Gondwana
  brong at fastmail.fm