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From Paul Davis <paul.joseph.da...@gmail.com>
Subject Re: Test suite errors
Date Fri, 19 Mar 2010 15:24:23 GMT
On Fri, Mar 19, 2010 at 8:41 AM, Robert Dionne
<dionne@dionne-associates.com> wrote:
>
>>
>> I got the error included below this morning, and when I ran it again, there was no
error.
>
>> /tmp/couchdb/0.11.0/test/etap/090-task-status.................ok
>> /tmp/couchdb/0.11.0/test/etap/100-ref-counter.................FAILED test 8
>
> I looked into this random fail a bit and it may be a real issue to consider. couch_ref_counter
uses process_info in the count function to compute the number of pids referring to the given
one, rather than interrogating the number of referrers being maintained in the state of the
gen_servers. This diff could explain the apparent race condition that caused this fail (which
doesn't reproduce on my box). From the who_calls trace it looks ok and I surmise the reason
process_info is used is to handle the case where a Pid dies in the forest and no one accounts
for it, throwing off the count, whereas process_info presumably never lies.
>
>

There was a possibility of a race condition in the test code. Seeing
as this is the first time I've heard of it being hit I reckon it must
be a fairly hard one to trigger. Anyway, new code should alleviate the
issue, and it was an error in the test itself, not the code so all is
well.

http://svn.apache.org/viewvc?revision=925264&view=revision

And a pretty diagram of the issue:

http://twitpic.com/19jk7a

The solution is to just make the Test process wait for a down message
that'd be triggered at the same time.

HTH,
Paul Davis

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