Re: [PATCH] lock_timeout and common SIGALRM framework

2012-04-10 09:02 keltezéssel, Boszormenyi Zoltan írta:
> 2012-04-06 14:47 keltezéssel, Cousin Marc írta:
>> On 05/04/12 08:02, Boszormenyi Zoltan wrote:
>>> 2012-04-04 21:30 keltezéssel, Alvaro Herrera írta:
>>>> I think this patch is doing two things: first touching infrastructure
>>>> stuff and then adding lock_timeout on top of that.  Would it work to
>>>> split the patch in two pieces?
>>>>
>>> Sure. Attached is the split version.
>>>
>>> Best regards,
>>> Zoltán Böszörményi
>>>
>> Hi,
>>
>> I've started looking at and testing both patches.
>>
>> Technically speaking, I think the source looks much better than the
>> first version of lock timeout, and may help adding other timeouts in the
>> future. I haven't tested it in depth though, because I encountered the
>> following problem:
>>
>> While testing the patch, I found a way to crash PG. But what's weird is
>> that it crashes also with an unpatched git version.
>>
>> Here is the way to reproduce it (I have done it with a pgbench schema):
>>
>> - Set a small statement_timeout (just to save time during the tests)
>>
>> Session1:
>> =#BEGIN;
>> =#lock TABLE pgbench_accounts ;
>>
>> Session 2:
>> =#BEGIN;
>> =#lock TABLE pgbench_accounts ;
>> ERROR:  canceling statement due to statement timeout
>> =# lock TABLE pgbench_accounts ;
>>
>> I'm using \set ON_ERROR_ROLLBACK INTERACTIVE by the way. It can also be
>> done with a rollback to savepoint of course.
>>
>> Session 2 crashes with this : TRAP : FailedAssertion(«
>> !(locallock->holdsStrongLockCount == 0) », fichier : « lock.c », ligne :
>> 749).
>>
>> It can also be done without a statement_timeout, and a control-C on the
>> second lock table.
>>
>> I didn't touch anything but this. It occurs everytime, when asserts are
>> activated.
>>
>> I tried it on 9.1.3, and I couldn't make it crash with the same sequence
>> of events. So maybe it's something introduced since ? Or is the assert
>> still valid ?
>>
>> Cheers
>>
>
> Attached are the new patches. I rebased them to current GIT and
> they are expected to be applied after Robert Haas' patch in the
> "bug in fast-path locking" thread.
>
> Now it survives the above scenario.
>
> Best regards,
> Zoltán Böszörményi

New patch attached, rebased to today's GIT.

Best regards,
Zoltán Böszörményi

--
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Zoltán Böszörményi
Cybertec Schönig&  Schönig GmbH
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