| From: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
|---|---|
| To: | Pavel Borisov <pashkin(dot)elfe(at)gmail(dot)com> |
| Cc: | Maxim Orlov <orlovmg(at)gmail(dot)com>, Alexander Korotkov <aekorotkov(at)gmail(dot)com>, wenhui qiu <qiuwenhuifx(at)gmail(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Postgres hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: POC: make mxidoff 64 bits |
| Date: | 2024-09-12 13:14:08 |
| Message-ID: | 202409121314.ilzhahahenkj@alvherre.pgsql |
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| Lists: | pgsql-hackers |
On 2024-Sep-12, Pavel Borisov wrote:
> Hi, Maxim!
>
> Previously we accessed offsets in shared MultiXactState without locks as
> 32-bit read is always atomic. But I'm not sure it's so when offset become
> 64-bit.
> E.g. GetNewMultiXactId():
>
> nextOffset = MultiXactState->nextOffset;
> is outside lock.
Good though. But fortunately I think it's not a problem. The one you
say is with MultiXactGetLock held in shared mode -- and that works OK,
as the assignment (in line 1263 at the bottom of the same routine) is
done with exclusive lock held.
--
Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/
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