From: Peter <pmc@citylink.dinoex.sub.org>
To: Andrew Gierth <andrew@tao11.riddles.org.uk>
Cc: pgsql-admin@postgresql.org
Cc: pgsql@FreeBSD.org
Subject: Re: Upgrade 10.5->10.6 : db crash BUS ERROR (sig 10), reproducible
Date: Fri, 8 Mar 2019 22:14:37 +0100
Message-ID: <20190308211437.GA86762@gate.oper.dinoex.org> (raw)
In-Reply-To: <87ef7hbal7.fsf@news-spur.riddles.org.uk>
References: <20190308012012.GA49481@gate.oper.dinoex.org>
<87lg1qaxr2.fsf@news-spur.riddles.org.uk>
<20190308152238.GA50588@gate.oper.dinoex.org>
<87ef7hbal7.fsf@news-spur.riddles.org.uk>
Hi Andrew,
many thanks for Your efforts!
Lets see what I get out of this. First, it seems I can reproduce the
fault on my build machine (IvyBridge core-i5) in the i386-chroot as
well - which is not a surprize according to Your explanations.
On Fri, Mar 08, 2019 at 04:51:47PM +0000, Andrew Gierth wrote:
! MOVAPS is an SSE (not SSE2) instruction; it's enabled by virtue of the
! fact that you used -march=pentium3 (the pentium3 supports SSE but not
! SSE2). The "A" stands for "aligned"; an unaligned source address causes
! an exception. %esp+0x20 is not correctly aligned for the instruction.
Okay so far. I was occasionally wondering if that pentium3 option
would effect anything at all. Now we see, it does. ;)
! GCC defaults to using a 16-byte stack alignment, but it relies on the
! caller to align the stack too, so if a GCC-compiled function is called
! from code that doesn't align the stack, then this kind of error can
! result. I do not know offhand (but I plan to find out) what clang's
! default stack alignment on i386 is.
Well, what caused me a headache this evening is: who would be the
caller in this case, as -from my understanding- it is just postgreSQL
running?
Now from Your newer mail this riddle does clear up well.
In my build environment, I can now create and start a new db-cluster
and issue only the single command "CREATE ROLE bacula;" and it will
crash - but then again I have to wait for the next checkpointer.
! You can tell GCC to realign the stack itself using the -mstackrealign
! option.
Yepp, that appears to solve it.
So, as there is a fix now, I'm pondering about who would be the
responsible to apply it?
* the system owner (alongside with the CPU definition)
* the port maintainer (alongside with the compiler choice)
* the postgres configure script
! This problem shows up only with GCC and not with clang because clang
! does not attempt to use SSE to vectorize this particular piece of code.
! The non-vectorized implementation generated by clang has no special
! requirements for stack alignment. But at the end of the day this is not
! a problem with PostgreSQL - it would show up with any code compiled with
! GCC where the compiler had elected to use SSE instructions for
! optimization.
Well, its clearly my fault, coming up with that pentium3 option. *gg*
rgds, P.
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To: pgsql-admin@postgresql.org
Cc: pmc@citylink.dinoex.sub.org, andrew@tao11.riddles.org.uk, pgsql@FreeBSD.org
Subject: Re: Upgrade 10.5->10.6 : db crash BUS ERROR (sig 10), reproducible
In-Reply-To: <20190308211437.GA86762@gate.oper.dinoex.org>
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