Horton

Re: [EXTERNAL] Re: Add non-blocking version of PQcancel

Thomas Munro <thomas.munro@gmail.com>

View thread View on postgr.es
From: Thomas Munro <thomas.munro@gmail.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Alexander Lakhin <exclusion@gmail.com>, Jelte Fennema-Nio <postgres@jeltef.nl>, Noah Misch <noah@leadboat.com>, Tom Lane <tgl@sss.pgh.pa.us>, Jacob Champion <jacob.champion@enterprisedb.com>, Denis Laxalde <denis.laxalde@dalibo.com>, vignesh C <vignesh21@gmail.com>, Greg Stark <stark@mit.edu>, "Gregory Stark (as CFM)" <stark.cfm@gmail.com>, Jelte Fennema <Jelte.Fennema@microsoft.com>, Daniel Gustafsson <daniel@yesql.se>, Peter Eisentraut <peter@eisentraut.org>, Andres Freund <andres@anarazel.de>, Justin Pryzby <pryzby@telsasoft.com>, Robert Haas <robertmhaas@gmail.com>, pgsql-hackers@lists.postgresql.org, Etsuro Fujita <etsuro.fujita@gmail.com>
Date: 2024-07-17T00:05:23Z
Lists: pgsql-hackers 
On Wed, Jul 17, 2024 at 3:08 AM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> Ugh.  I tried to follow what's going on in that cygwin code, but I gave
> up pretty quickly.  It depends on a mutex, but I didn't see the mutex
> being defined or initialized anywhere.

https://github.com/cygwin/cygwin/blob/cygwin-3.5.3/winsup/cygwin/fhandler/socket_inet.cc#L217C1-L217C77

Not obvious how it'd be deadlocking (?), though...  it's hard to see
how anything between LOCK_EVENTS and UNLOCK_EVENTS could escape/return
early.  (Something weird going on with signal handlers?  I can't
imagine where one would call poll() though).

Commits

  1. postgres_fdw: re-issue cancel requests a few times if necessary.

  2. Make postgres_fdw's query_cancel test less flaky.

  3. postgres_fdw: Split out the query_cancel test to its own file

  4. Fix copy-paste mistake in PQcancelCreate

  5. Make libpqsrv_cancel's return const char *, not char *

  6. Stabilize postgres_fdw test

  7. libpq-be-fe-helpers.h: wrap new cancel APIs

  8. dblink/isolationtester/fe_utils: Use new cancel API

  9. Put libpq_pipeline cancel test back

  10. Hopefully make libpq_pipeline's new cancel test more reliable

  11. libpq: Add encrypted and non-blocking query cancellation routines

  12. libpq: Move pg_cancel to fe-cancel.c

  13. Add tests for libpq query cancellation APIs

  14. Add missing connection statuses to docs

  15. libpq: Change some static functions to extern

  16. libpq: Add pqReleaseConnHosts function

  17. libpq: Move cancellation related functions to fe-cancel.c

  18. Make spelling of cancelled/cancellation consistent

  19. Be more wary about OpenSSL not setting errno on error.

  20. libpq: Use modern socket flags, if available.

  21. Drop test view when done with it.

  22. Doc: add some doco about using the libpq_pipeline test module.

  23. postgres_fdw: Allow cancellation of transaction control commands.