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From: "Ondřej Bílka" <>
To: Mike Frysinger <>
Subject: Re: [RFC][BZ #1874] Fix assertion triggered by thread/fork interaction
Date: Thu, 02 Jan 2014 23:54:00 -0000	[thread overview]
Message-ID: <20140102235440.GB5026@domone> (raw)
In-Reply-To: <>

On Thu, Jan 02, 2014 at 05:18:22PM -0500, Mike Frysinger wrote:
> On Wednesday 09 October 2013 16:05:34 Ondřej Bílka wrote:
> > Details:
> > 
> > If a thread happens to hold dl_load_lock and have r_state set to RT_ADD
> > or RT_DELETE at the time another thread calls fork(), then the child exit
> > code from fork (in nptl/sysdeps/unix/sysv/linux/fork.c in our case)
> > re-initializes dl_load_lock but does not restore r_state to RT_CONSISTENT.
> > If the child subsequently requires functionality before calling
> > exec(), then the assertion will fire.
> > 
> > The patch acquires dl_load_lock on entry to fork() and releases it on exit
> > from the parent path.  The child path is initialized as currently done.
> > This is essentially pthreads_atfork, but forced to be first because the
> > acquisition of dl_load_lock must happen before malloc_atfork is active
> > to avoid a deadlock.
> > "
> doesn't seem right that we grab the lock and then just reset it in the child ?  
> seems like you should just unlock it rather than reset it in the child.
That part looks ok as without locking you could get inconsistent linker structures. 

> i'm also wary of code that already grabs a lot of locks trying to grab even 
> more.  the code paths that already grab the IO locks ... can they possibly 
> grab this one too ?  like a custom format handler that triggers loading of 
> libs ?
Do you haave a better solution? I send this to decide what to do with
this bug. I would not be surprised if we decided that it is invalid as
threads with fork cause problems in general.

  reply	other threads:[~2014-01-02 23:54 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-10-09 20:05 Ondřej Bílka
2013-10-17 15:41 ` Ondřej Bílka
2014-01-02 20:30 ` [PING][RFC][BZ " Ondřej Bílka
2014-01-02 22:18 ` [RFC][BZ " Mike Frysinger
2014-01-02 23:54   ` Ondřej Bílka [this message]
2014-01-03  2:07     ` Mike Frysinger
2014-01-11 12:07       ` Ondřej Bílka

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