| From: | Andrey Borodin <x4mmm(at)yandex-team(dot)ru> |
|---|---|
| To: | Alexander Korotkov <aekorotkov(at)gmail(dot)com> |
| Cc: | Michael Paquier <michael(at)paquier(dot)xyz>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Pavel Borisov <pashkin(dot)elfe(at)gmail(dot)com>, Victor Yegorov <vyegorov(at)gmail(dot)com>, Yura Sokolov <y(dot)sokolov(at)postgrespro(dot)ru>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Andres Freund <andres(at)anarazel(dot)de>, Kirill Reshke <reshke(at)yandex-team(dot)ru> |
| Subject: | Re: Get rid of WALBufMappingLock |
| Date: | 2025-02-26 08:52:17 |
| Message-ID: | C27929F1-4932-42A1-8B9B-EACBEEBDB0EB@yandex-team.ru |
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| Lists: | pgsql-hackers |
> On 25 Feb 2025, at 20:19, Alexander Korotkov <aekorotkov(at)gmail(dot)com> wrote:
>
>
Hi!
One little piece of code looks suspicious to me. But I was not raising concern because I see similar code everywhere in the codebase. But know Kirill asked to me explain what is going on and I cannot.
This seems to be relevant… so.
+ while (upto >= pg_atomic_read_u64(&XLogCtl->InitializedUpTo))
// Assume ConditionVariableBroadcast() happened here, but before next line
+ ConditionVariableSleep(&XLogCtl->InitializedUpToCondVar, WAIT_EVENT_WAL_BUFFER_INIT);
+ ConditionVariableCancelSleep();
Won’t this sleep wait forever?
I see about 20 other occurrences of similar code, so, perhaps, everything is fine. But I would greatly appreciate a little pointers on why it works.
Best regards, Andrey Borodin.
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