Sunday, August 24, 2008

Race condition or Antivirus ?

Hi folks,
What happens if on your voting machine is running an AV ? Maybe it will disturb your election like they say or maybe having an AV is a good ting but your voting system is logically bugged and the problem is still deep.

Joe Hall has the details. Check it here. The Premier reports aren't that clear. Here's the "technical background".
The GEMS poster works by receiving concurrent uploads from the memory cards and then saving that data in temporary files for posting to the election databse in a serialized manner, i.e. one at a time. This design is used to optimize the database access performance as well as the upload data performance.
The issue identified is a logic error that allows the poster to attempt to post a file that is still being received when two or more files are received in sequence, and the first file takes longer to save than the second file. If a sharing violation occures, the posting of the first file is the one affected. Note that files typically take very few milliseconds to save, whereas large files, with large number of votes, can take up to 100 milliseconds.

So it seems a common problem of race condition in concurrent distributed system. It's worth asking if there are ways where the file would be marked successfully uploaded but the votes get lost ??

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