Re: (ITS#7723) slapd crashes on multi core machines if a search request is *immediately* followed by an unbind

[hyc@symas.com]

jsynacek@redhat.com wrote:
> On 10/15/2013 01:10 PM, michael.vishchers@7p-group.com wrote:
>> It is not the client loop that is multithreading but the ldap server.
>>
>> And it is not a misuse of the API but a problem that may be raised by day t=
>> o day network problems.
>>
>> I've boiled down the problem to a few simple configurations that work (or b=
>> etter, fail ;-) with both 2.4.23 and 2.4.36. A tgz file containing a setup =
>> with start script and testclient is attached. It should be sufficient to re=
>> produce the fault.
>>
>> The problem occurs only if we use session variable substitution in the rwm =
>> overlay, and only if a search is *immediately* (e.g. caused by network loss=
>>   and client timeout) followed by an unbind.
>>
>
> I modified the reproducer a bit (the start script) and find out a few things.
> You can find the reproducer I'm using at [1].
>
> Valgrind's helgrind shows some lock problems in the rwm overlay and also in
> back-ldap and connection.c. After correcting those the issue seems to be gone.
>
> You can find helgrind logs at [2] (before the fix) and [3] (after).
>
> Also, ElectricFence reveals some problems [4], which I didn't fix yet.
>
> A fix attempt can be found at [5]. I'm not sure if that is a correct fix, or it
> just masked the real issue. But I didn't to manage to reproduce the problem
> after applying it.

I already explained the problem. The other issues you identified are not 
relevant, and your patch is not correct. Reread Followup #4 of this ITS.

-- 
   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
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