MIME-Version: 1.0
References: <CACG=ezaWg7_nt-8ey4aKv2w9LcuLthHknwCawmBgEeTnJrJTcw@mail.gmail.com>
 <ff143b24-a093-40da-9833-d36b83726bdf@iki.fi> <CAGjGUAKO1GCzG5wBMt5RosWo0PatgFpYY=Gjgt77tN2brNe=Bg@mail.gmail.com>
 <CACG=ezYokoiumOFnqUfg_ffHD5s8T+6iHYfzKLfa=QQ-1pNrBg@mail.gmail.com>
 <CACG=ezY9xq73jcX_EjVqx5-f90nbQ9PyhFCTW2fwFCS2wmNiFw@mail.gmail.com>
 <CACG=eza+27CfLBobJJccRhXrA3He6c1irAnoyTtSC1-z9UXLrg@mail.gmail.com>
 <CAPpHfduczcop9s6gKUpLGgFUe2y4ERGMJx6SS6Kp+s-kQPwMjg@mail.gmail.com>
 <CACG=ezbye4g_ERNqE=gBcvQ0YypRaVENhNUu8xrs4PL12UdnUA@mail.gmail.com> <CACG=ezaMncd0-BcGHBgsSR2eqHfrz9WznHGLKX8biz6zu-azGw@mail.gmail.com>
In-Reply-To: <CACG=ezaMncd0-BcGHBgsSR2eqHfrz9WznHGLKX8biz6zu-azGw@mail.gmail.com>
From: Pavel Borisov <pashkin.elfe@gmail.com>
Date: Thu, 12 Sep 2024 16:09:08 +0400
Message-ID: <CALT9ZEHm138m2rTi6-N_Xcm0ibfbK0b7yysdPHj1v144YUOFQg@mail.gmail.com>
Subject: Re: POC: make mxidoff 64 bits
To: Maxim Orlov <orlovmg@gmail.com>
Cc: Alexander Korotkov <aekorotkov@gmail.com>, wenhui qiu <qiuwenhuifx@gmail.com>, 
	Heikki Linnakangas <hlinnaka@iki.fi>, Postgres hackers <pgsql-hackers@lists.postgresql.org>
Content-Type: multipart/alternative; boundary="000000000000ee6a8c0621eaf987"
Archived-At: <https://www.postgresql.org/message-id/CALT9ZEHm138m2rTi6-N_Xcm0ibfbK0b7yysdPHj1v144YUOFQg%40mail.gmail.com>
Precedence: bulk

--000000000000ee6a8c0621eaf987
Content-Type: text/plain; charset="UTF-8"

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.

There might be other places we do the same as well.

Regards,
Pavel Borisov
Supabase

--000000000000ee6a8c0621eaf987
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div dir=3D"ltr">Hi, Maxim!</div><div class=3D"gmail_quote=
"><div><br></div><div>Previously we accessed offsets in shared MultiXactSta=
te without locks as 32-bit read is always atomic. But I&#39;m not sure it&#=
39;s so when offset become 64-bit.</div><div>E.g.=C2=A0GetNewMultiXactId():=
</div><div><br></div><div>nextOffset =3D MultiXactState-&gt;nextOffset;</di=
v><div>is outside lock.=C2=A0</div><div><br></div><div>There might be other=
 places we do the same as well.=C2=A0</div><div><br></div><div>Regards,</di=
v><div>Pavel Borisov</div><div>Supabase</div><div><br></div><div><br></div>=
</div></div>

--000000000000ee6a8c0621eaf987--