Re: pgsql: Add function to log the memory contexts of specified backend pro

Fujii Masao <masao.fujii@oss.nttdata.com>

From: Fujii Masao <masao.fujii@oss.nttdata.com>

To: Robert Haas <robertmhaas@gmail.com>

Cc: torikoshia <torikoshia@oss.nttdata.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>

Date: 2025-07-14T13:53:38Z

Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Add guard to prevent recursive memory context logging.
- 1a9a49699c21 14.21 landed
- 0fc2f533a96c 15.16 landed
- 3853f61681e8 16.12 landed
- 699293d2749a 17.8 landed
- b863d8d87fc1 18.2 landed
- b3ccb0a2cb2e 19 (unreleased) landed
Add function to log the memory contexts of specified backend process.
- 43620e328617 14.0 cited
Add pg_backend_memory_contexts system view.
- 3e98c0bafb28 14.0 cited

Attachments

v4-0001-PG14-PG16-Add-guard-to-prevent-recursive-memory-context-log.txt (text/plain)
v4-0001-PG17-master-Add-guard-to-prevent-recursive-memory-context-log.patch (text/plain) patch v4-0001


On 2025/05/07 18:06, Fujii Masao wrote:
> 
> 
> On 2025/05/05 23:57, Robert Haas wrote:
>> On Fri, May 2, 2025 at 9:54 PM Fujii Masao <masao.fujii@oss.nttdata.com> wrote:
>>> Thanks for the review and testing! I've fixed the issue you pointed out.
>>> Updated patch attached.
>>
>> Thanks for addressing this. However, I believe this commit may need to
>> take note of the following comment from elog.h:
> 
> Thanks for the review!
> 
> 
>>   * Note: if a local variable of the function containing PG_TRY is modified
>>   * in the PG_TRY section and used in the PG_CATCH section, that variable
>>   * must be declared "volatile" for POSIX compliance.  This is not mere
>>   * pedantry; we have seen bugs from compilers improperly optimizing code
>>   * away when such a variable was not marked.  Beware that gcc's -Wclobbered
>>   * warnings are just about entirely useless for catching such oversights.
>>
>> Based on this comment, I believe in_progress must be declared volatile.
> 
> You're right. OTOH, setting the flag inside the PG_TRY() block isn't necessary,
> so I've moved it outside instead of leaving it inside and marking the flag volatile.
> 
> 
>> As a stylistic comment, I think I would prefer making in_progress a
>> file-level global and giving it a less generic name (e.g.
>> LogMemoryContextInProgress). However, perhaps others will disagree.
> 
> I'm fine with this. I've renamed the flag and made it a file-level global
> variable as suggested. Updated patch is attached.

I've attached the rebased versions of the patches.

The patch for v14–v16 is labeled with a .txt extension to prevent cfbot
from treating it as a patch for master, which would cause it to fail
when applying.

Regards,

-- 
Fujii Masao
NTT DATA Japan Corporation