Horton

Re: Non-reproducible AIO failure

Konstantin Knizhnik <knizhnik@garret.ru>

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From: Konstantin Knizhnik <knizhnik@garret.ru>
To: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2025-06-12T12:12:00Z
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 →

  1. aio: Stop using enum bitfields due to bad code generation

  2. amcheck: Fix posting tree checks in gin_index_check()

  3. aio: Add missing memory barrier when waiting for IO handle

Reproduced it once again with with write-protected io handle.
But once again - no access violation, just assert failure.

Previously "op" field was overwritten somewhere between 
`pgaio_io_reclaim` and `AsyncReadBuffers`:

!!!pgaio_io_reclaim [20376]| ioh: 0x1019bc000, ioh->op: 0, 
ioh->generation: 19346
!!!AsyncReadBuffers [20376] (1)| blocknum: 21, ioh: 0x1019bc000, 
ioh->op: 1, ioh->state: 1, ioh->result: 0, ioh->num_callbacks: 0, 
ioh->generation: 19346

Now it is overwritten after print in AsyncReadBuffers:

!!!pgaio_io_reclaim [88932]| ioh: 0x105a5c000, ioh->op: 0, 
ioh->generation: 42848
!!!pgaio_io_acquire_nb[88932]| ioh: 0x105a5c000, ioh->op: 0, 
ioh->generation: 42848
!!!AsyncReadBuffers [88932] (1)| blocknum: 10, ioh: 0x105a5c000, 
ioh->op: 0, ioh->state: 1, ioh->result: 0, ioh->num_callbacks: 0, 
ioh->generation: 42848
!!!pgaio_io_before_start| ioh: 0x105a5c000, ioh->op: 1, ioh->state: 1, 
ioh->result: 0, ioh->num_callbacks: 2, ioh->generation: 42848

In this run I prohibit writes to io handle in `pgaio_io_acquire_nb` and 
reenable them in `AsyncReadBuffer`.