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From: Mike Frysinger <>
Cc: "Ondřej Bílka" <>,
Subject: Re: [RFC][BZ #1874] Fix assertion triggered by thread/fork interaction
Date: Thu, 02 Jan 2014 22:18:00 -0000	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <20131009200534.GA4300@domone.podge>

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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.

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 ?

> +  /* grab lock BEFORE switching to malloc_atfork */

comment style is incorrect

> +      /* unlock last, because we locked it first */

comment style is wrong here too

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  parent reply	other threads:[~2014-01-02 22:18 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 ` Mike Frysinger [this message]
2014-01-02 23:54   ` [RFC][BZ " Ondřej Bílka
2014-01-03  2:07     ` Mike Frysinger
2014-01-11 12:07       ` Ondřej Bílka

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