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From: Eric Wong <e@80x24.org>
To: Jeremy Evans <code@jeremyevans.net>
Cc: Pere Joan Martorell <pere.joan@camaloon.com>,
	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

> 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:

(**) similar story with lock-free multi-threading in other projects

  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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