Re: EINTR in ftruncate()

On 2022-Jul-01, Andres Freund wrote:

> On 2022-07-01 17:41:05 +0200, Alvaro Herrera wrote:
> > Nicola Contu reported two years ago to pgsql-general[1] that they were
> > having sporadic query failures, because EINTR is reported on some system
> > call. I have been told that the problem persists, though it is very
> > infrequent. I propose the attached patch. Kyotaro proposed a slightly
> > different patch which also protects write(), but I think that's not
> > necessary.
>
> What is the reason for the || ProcDiePending || QueryCancelPending bit? What
> if there's dsm operations intentionally done while QueryCancelPending?

That mirrors the test for the other block in that function, which was
added by 63efab4ca139, whose commit message explains:

Allow DSM allocation to be interrupted.

Chris Travers reported that the startup process can repeatedly try to
cancel a backend that is in a posix_fallocate()/EINTR loop and cause it
to loop forever. Teach the retry loop to give up if an interrupt is
pending. Don't actually check for interrupts in that loop though,
because a non-local exit would skip some clean-up code in the caller.

Thanks for looking!

--
Álvaro Herrera PostgreSQL Developer — https://www.EnterpriseDB.com/