From: Eric Wong <e@80x24.org>
To: Jeremy Evans <code@jeremyevans.net>
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
Date: Sat, 15 Jul 2017 00:15:35 +0000 [thread overview]
Message-ID: <20170715001535.GA8205@starla> (raw)
In-Reply-To: <20170714225015.GD68067@jeremyevans.local>
Jeremy Evans <code@jeremyevans.net> wrote:
> Thanks for this patch. I'm not an RB_GC_GUARD expert, but the changes
> look fine to me. The existing RB_GC_GUARD calls were added by me in
> 2012 to fix an earlier segfault.[1] This is the first reported
> RB_GC_GUARD-related segfault in sequel_pg since then.
No worries; I don't consider myself a RB_GC_GUARD expert, either(*).
> [1] https://github.com/jeremyevans/sequel_pg/commit/15edb132887d9b5292cad419fc7692ed5cd4b01b.diff
I suspect your original guards were lucky enough for C compilers
in 2012, but compilers have gotten more clever since then. So
there's a a higher likelyhood of exposing bugs given the
conservative GC in Ruby(**).
Historical note:
Back in the day, "volatile" alone was enough to defeat
compiler optimizations in C Ruby. Eventually, compilers got
better, so RB_GC_GUARD was introduced. And in the future,
RB_GC_GUARD may evolve to accomodate even more clever
compilers.
> Pere, I would appreciate if you could test this patch and see if it
> fixes your issue. I will also test it and will release a new sequel_pg
> version with this patch if it fixes the issue.
Yes, actually testing the code is important, everything else
I've written here is theory ;)
(*) Fwiw, I am not fluent in reading asm for systems I run Ruby on,
but I know how clever compilers can be, and have written
about it some on ruby-core:
https://public-inbox.org/ruby-core/?q=RB_GC_GUARD&d:..20170714
(**) similar story with lock-free multi-threading in other projects
next prev parent reply other threads:[~2017-07-15 0:15 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-13 18:48 Random crash when sending USR2 + QUIT signals to Unicorn process Pere Joan Martorell
2017-07-13 19:34 ` Eric Wong
2017-07-14 10:21 ` Pere Joan Martorell
2017-07-14 21:16 ` Eric Wong
2017-07-14 22:50 ` Jeremy Evans
2017-07-15 0:15 ` Eric Wong [this message]
2017-07-15 1:34 ` Jeremy Evans
2017-07-15 4:45 ` Eric Wong
2017-07-15 7:56 ` Jeremy Evans
2017-07-17 14:32 ` Jeremy Evans
2017-07-24 1:25 ` Eric Wong
2017-08-07 6:16 ` Jeremy Evans
2017-08-07 20:18 ` Eric Wong
2017-10-03 14:52 ` Xuanzhong Wei
2017-10-03 17:15 ` Eric Wong
2017-10-03 18:20 ` Xuanzhong Wei
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