Date: Fri, 27 Mar 2020 20:34:34 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Masahiko Sawada <masahiko.sawada@2ndquadrant.com>,
	Alvaro Herrera <alvherre@2ndquadrant.com>,
	Andres Freund <andres@anarazel.de>,
	Michael Paquier <michael@paquier.xyz>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: error context for vacuum to include block number
Message-ID: <20200328013434.GZ20103@telsasoft.com>
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On Sat, Mar 28, 2020 at 06:59:10AM +0530, Amit Kapila wrote:
> On Sat, Mar 28, 2020 at 6:46 AM Justin Pryzby <pryzby@telsasoft.com> wrote:
> >
> > On Sat, Mar 28, 2020 at 06:28:38AM +0530, Amit Kapila wrote:
> > > > Hm, but I caused a crash *without* adding CHECK_FOR_INTERRUPTS, just
> > > > kill+sleep.  The kill() could come from running pg_cancel_backend().  And the
> > > > sleep() just encourages a context switch, which can happen at any time.
> > >
> > > pg_sleep internally uses CHECK_FOR_INTERRUPTS() due to which it would
> > > have accepted the signal sent via pg_cancel_backend().  Can you try
> > > your scenario by temporarily removing CHECK_FOR_INTERRUPTS from
> > > pg_sleep() or maybe better by using OS Sleep call?
> >
> > Ah, that explains it.  Right, I'm not able to induce a crash with usleep().
> >
> > Do you want me to resend a patch without that change ?  I feel like continuing
> > to trade patches is more likely to introduce new errors or lose someone else's
> > changes than to make much progress.  The patch has been through enough
> > iterations and it's very easy to miss an issue if I try to eyeball it.
> 
> I can do it but we have to agree on the other two points (a) I still
> feel that switching to the truncate phase should be done at the place
> from where we are calling lazy_truncate_heap and (b)
> lazy_cleanup_index should switch back the error phase after calling
> index_vacuum_cleanup.  I have explained my reasoning for these points
> a few emails back.

I have no objection to either.  It was intuitive to me to do it how I
originally wrote it but I'm not wedded to it.

-- 
Justin