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Date: Sun, 6 Aug 2017 23:16:58 -0700
From: Jeremy Evans <code@jeremyevans.net>
To: Eric Wong <e@80x24.org>
Cc: Pere Joan Martorell <pere.joan@camaloon.com>,
	unicorn-public@bogomips.org,
	Philip Cunningham <philip@irisconnect.co.uk>,
	Jonathan del Strother <maillist@steelskies.com>
Subject: Re: Random crash when sending USR2 + QUIT signals to Unicorn process
Message-ID: <20170807061658.GA83366@jeremyevans.local>
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On 07/24 01:25, Eric Wong wrote:
> Jeremy Evans <code@jeremyevans.net> wrote:
> > Running with GC.stress didn't catch the error for me.  But I'm using a
> > fairly old compiler (GCC 4.2.1, the OpenBSD default), so this may be
> > something that only shows up on a newer compiler that does more
> > optimizations.
> 
> Pere: just curious if you've had a chance to test my patch for
> sequel_pg from Jeremy's latest sequel_pg.git
> 
> In any case, I'm certain my patch fixes a bug which manifests
> in a compiler-dependent manner; but here could always be other
> bugs in a similar vein.  Thanks.

I can't get it to crash with sequel_pg 1.7.0 when compiled using clang
4.0.0 either.  I even tried to build a special program designed to
trigger the crash.

Compiler used:

$ cc -v
OpenBSD clang version 4.0.0 (tags/RELEASE_400/final) (based on LLVM 4.0.0)
Target: amd64-unknown-openbsd6.1
Thread model: posix
InstalledDir: /usr/bin

Program used:

require 'sequel'
DB = Sequel.postgres(:test=>false)
DB.extension :pg_array
# pg_array.txt contains ([[1] * 100] * 100) in PostgreSQL array format
t = File.read('pg_array.txt')
dot = '.'
trap(:HUP){}
Thread.new do
  while true
    sleep 1
    Process.kill(:HUP, $$)
  end
end
GC.stress = true
(0..2).map do
  Thread.new do
    i = 0
    pr = lambda{|v| print dot if ((i+=1) % 100) == 0; "#{v}#{v}"}
    while true
      print 'L'
      Sequel::Postgres.parse_pg_array(t.dup, pr)
    end
  end
end.map(&:join)

Pere, can you test this program and see if it crashes in your
environment?  If not, can you put together a reproducible example that
does crash in your environment?

Thanks,
Jeremy