From owner-freebsd-hackers@FreeBSD.ORG  Thu Mar 19 03:58:07 2009
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Date: Thu, 19 Mar 2009 12:00:22 +0800
From: David Xu <davidxu@freebsd.org>
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To: Kostik Belousov <kostikbel@gmail.com>
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Cc: Daniel Eischen <deischen@freebsd.org>, David Schultz <das@freebsd.org>,
	hackers@freebsd.org, Jason Evans <jasone@freebsd.org>,
	Julian Elischer <julian@elischer.org>
Subject: Re: threaded, forked, rethreaded processes will deadlock
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Kostik Belousov wrote:
> I looked at the issue once more recently, and I propose the following
> much less intrusive patch. It is somewhat hackish, but I think that
> it would be good to have this working. Most other Unixes do have
> working thread library after the fork. Any objections ?
> 
> diff --git a/lib/libthr/thread/thr_fork.c b/lib/libthr/thread/thr_fork.c
> index bc410d1..ae6b9ad 100644
> --- a/lib/libthr/thread/thr_fork.c
> +++ b/lib/libthr/thread/thr_fork.c
> @@ -173,14 +173,19 @@ _fork(void)
>  		/* Ready to continue, unblock signals. */ 
>  		_thr_signal_unblock(curthread);
>  
> -		if (unlock_malloc)
> +		if (unlock_malloc) {
> +			__isthreaded = 1;
>  			_malloc_postfork();
> +			__isthreaded = 0;
> +		}
>  
>  		/* Run down atfork child handlers. */
>  		TAILQ_FOREACH(af, &_thr_atfork_list, qe) {
>  			if (af->child != NULL)
>  				af->child();
>  		}
> +
> +		THR_UMUTEX_UNLOCK(curthread, &_thr_atfork_lock);

^^^
This line is not needed.

>  	} else {
>  		/* Parent process */
>  		errsave = errno;