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[perl #124203] debugging threaded perl hangs with perl-5.20.2

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From:
Tony Cook via RT
Date:
February 26, 2019 03:19
Subject:
[perl #124203] debugging threaded perl hangs with perl-5.20.2
Message ID:
rt-4.0.24-17597-1551151148-855.124203-15-0@perl.org
On Tue, 14 Apr 2015 23:26:52 -0700, tonyc wrote:
> On Tue Apr 14 21:38:57 2015, tonyc wrote:
> > On Tue Apr 14 17:31:32 2015, tonyc wrote:
> > > tony@mars:.../git/perl$ PERL5DB_THREADED=1 ./perl -Ilib -d
> >
> > -dt is implemented as setting PERL5DB_THREADED=1 so this is the same
> > as
> > #124203, so I've merged it in, since I've provided backtrace info.
> >
> > Note that the problem still occurred with both my AV fix and the
> > dummy
> > lock() fix.
> 
> 5.14.2 also locks up in the same place, this is an old issue.
> 
> 5.8.9 locks up when cleaning up the old thread:

I tried bisecting this issue, and it found:

commit 2cbb2ee1d6d1dc9f375107de4b70573ece8a4e13
Author: Rafael Garcia-Suarez <rgarciasuarez@gmail.com>
Date:   Fri Oct 15 14:09:54 2004 +0000

    Implement a new -dt command-line flag, to enable threads under the
    debugger (bug #31666).
    
    Subject: RE: [PATCH] debugger handles threads [perl #31666]
    From: <richard.foley@ubs.com>
    Date: Wed, 13 Oct 2004 13:01:18 +0200
    Message-ID: <B374141B0A424D4F9CF143CC51B3ADD903FB9E12@NZURC900PEX1.ubsgs.ubsgroup.net>
    
    Subject: Re: [PATCH] debugger handles threads [perl #31666]
    From: Yitzchak Scott-Thoennes <sthoenna@efn.org>
    Date: Wed, 13 Oct 2004 02:49:58 -0700
    Message-ID: <20041013094957.GA17184@efn.org>
    
    p4raw-id: //depot/perl@23372

which is when the -dt switch and threads support in the debugger was added.

The change from lock-up only during clean up vs lock up when starting the child thread was in:

commit 9ca4d7fde651f30cf17f7ba4156d78a9cc604ae0
Author: Jerry D. Hedden <jdhedden@cpan.org>
Date:   Sun Sep 10 02:12:06 2006 -0700

    Race condition fix in threads.pm
    First patch from:
    
    Subject: [PATCH] thread 1.41 - A drama in three parts
    From: "Jerry D. Hedden" <jdhedden@cpan.org>
    Message-ID: <20060910091206.fb30e530d17747c2b054d625b8945d88.321c7cbc94.wbe@email.secureserver.net>
    
    p4raw-id: //depot/perl@28833

so unless there was a tool change (compiler, libc) that introduced this at some point, I don't see that it ever worked.

Tony

---
via perlbug:  queue: perl5 status: open
https://rt.perl.org/Ticket/Display.html?id=124203

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