Re: Get memory contexts of an arbitrary backend process

On 2021/03/04 18:32, torikoshia wrote:
> On 2021-01-14 19:11, torikoshia wrote:
>> Since pg_get_target_backend_memory_contexts() waits to dump memory and
>> it could lead dead lock as below.
>>
>>   - session1
>>   BEGIN; TRUNCATE t;
>>
>>   - session2
>>   BEGIN; TRUNCATE t; -- wait
>>
>>   - session1
>>   SELECT * FROM pg_get_target_backend_memory_contexts(<pid of session
>> 2>); --wait
>>
>>
>> Thanks for notifying me, Fujii-san.
>>
>>
>> Attached v8 patch that prohibited calling the function inside transactions.
>
> Regrettably, this modification could not cope with the advisory lock and
> I haven't come up with a good way to deal with it.
>
> It seems to me that the architecture of the requestor waiting for the
> dumper leads to this problem and complicates things.
>
>
> Considering the discussion printing backtrace discussion[1], it seems
> reasonable that the requestor just sends a signal and dumper dumps to
> the log file.

+1

Regards,

--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION