Hi! Thanks for the review! Its true that qtext_load_file() can be called with acquired lock in pg_stat_statements_internal()… So I perform INTERRUPTS_PENDING_CONDITION in v2 patch and call CHECK_FOR_INTERRUPTS later, after cycle ended and lock released.
v2-cancelable-qtext_load_file.patch
Description: Binary data
> On 28 Apr 2025, at 11:16, Andrey Borodin <x4...@yandex-team.ru> wrote: > > > >> On 24 Apr 2025, at 22:49, Roman Khapov <rkha...@yandex-team.ru> wrote: >> >> Hi! >> Recently we faced a problem in out production psql installation, which was >> that we had to cancel all requests to the db, including performance >> monitoring requests, that uses ps_stat_statements. But we could not cancel >> the request in usual way, and had to kill -9 the pg process of it. > > Interesting problem, thanks for raising it! > >> We've noticed that the the query execution stuck on PGSS_TEXT_FILE file >> reading in function qtext_load_file, which doesn't have CHECK_FOR_INTERRUPTS >> in the read cycle. In addition to our case with large PGSS_TEXT_FILE (and >> maybe the problems with virtual disk i/o) that can explain uncancellable >> pg_stat_statements queries. > > I'm afraid it might be not so easy to add CHECK_FOR_INTERRUPTS there. Most > probably you was holding a LWLockAcquire(pgss->lock, LW_SHARED) somewhere (do > you have a backtrace?), which prevent interrupts anyway. > > Thanks! > > > Best regards, Andrey Borodin.
