Re: SpinLockAcquire and SpinLockRelease is broken on ARM/ARM64? (Re: sinvaladt.c: remove msgnumLock, use atomic operations on maxMsgNum) - Mailing list pgsql-hackers

From Andres Freund
Subject Re: SpinLockAcquire and SpinLockRelease is broken on ARM/ARM64? (Re: sinvaladt.c: remove msgnumLock, use atomic operations on maxMsgNum)
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Msg-id ksopwquxxtr27apbzxttm4xkw56vhu5xdh7ogfbqrdw4q6qvm2@etdo37vtfoys
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In response to Re: sinvaladt.c: remove msgnumLock, use atomic operations on maxMsgNum  (Yura Sokolov <y.sokolov@postgrespro.ru>)
List pgsql-hackers
Hi,

On 2025-06-02 21:20:33 +0300, Yura Sokolov wrote:
> But still problem of spin lock contention is here.

I still would like to see a reproducer for this.


> So I propose to introduce another spin lock type capable for Exclusive and
> Shared lock modes (i.e. Write/Read modes) and use it in this two places.

I am vehemently opposed to that. We should work towards getting rid of
spinlocks, not introduce more versions of spinlocks. Userspace spinlocks
largely are a bad idea. We should instead make properly queued locks cheaper
(e.g. by having an exclusive-only lock, which can be cheaper to release on
common platforms).

Greetings,

Andres Freund



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