Re: BackendPidGetProc doesn't return PGPROC for background worker?

On 2015-05-15 AM 10:59, Amit Langote wrote:
> On 2015-05-15 AM 10:39, Amit Langote wrote:
>> On 2015-05-15 AM 05:01, Pavel Stehule wrote:
>>>
>>> I am trying to start bgworker from bgworker and create communication
>>> between these process. I have a code based on test_shm_mq. This code fails
>>> because BackendPidGetProc doesn't find related bgworker process, although
>>> the registrant process is living
>>>
>>
>> One reason for this may be that the worker was not started with the flag
>> BGWORKER_SHMEM_ACCESS which is necessary to perform InitProcess() that would
>> initialize a PGPROC entry for it. But if you'd used the same method for
>> initializing workers as test_shm_mq_setup(), then it should have.
>>
> 
> It seems in addition, a BackgroundWorkerInitializeConnection() is also
> necessary for the PGPROC entry of the worker to be visible to others. I do not
> see that done anywhere in test_shm_mq(); so perhaps that's missing?
> 

And these conditions apply to the bgworker that started another bgworker, that
is the registrant bgworker. I think such a pattern does not exist in existing
code. That is, normally all workers are started by a user backend that has a
valid shared PGPROC entry.

Thanks,
Amit