From owner-freebsd-hackers@FreeBSD.ORG  Fri Nov 22 15:21:06 2013
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Message-ID: <528F765A.8040306@gmail.com>
Date: Fri, 22 Nov 2013 17:20:58 +0200
From: Vitaly Magerya <vmagerya@gmail.com>
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To: Jilles Tjoelker <jilles@stack.nl>, 
 Konstantin Belousov <kostikbel@gmail.com>
Subject: Re: Problem with signal 0 being delivered to SIGUSR1 handler
References: <528DFEE6.6020504@gmail.com> <20131121211546.GQ59496@kib.kiev.ua>
 <20131122133553.GA28457@stack.nl>
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On 11/22/2013 15:35, Jilles Tjoelker wrote:
> This patch fixes the problem for me on stable/9 and head.
> 
> Index: lib/libthr/thread/thr_sig.c
> ===================================================================
> --- lib/libthr/thread/thr_sig.c	(revision 258178)
> +++ lib/libthr/thread/thr_sig.c	(working copy)
> @@ -326,12 +326,12 @@ check_deferred_signal(struct pthread *curthread)
>  	uc_len = __getcontextx_size();
>  	uc = alloca(uc_len);
>  	getcontext(uc);
> -	if (curthread->deferred_siginfo.si_signo == 0)
> -		return;
>  	__fillcontextx2((char *)uc);
>  	act = curthread->deferred_sigact;
>  	uc->uc_sigmask = curthread->deferred_sigmask;
>  	memcpy(&info, &curthread->deferred_siginfo, sizeof(siginfo_t));
> +	if (curthread->deferred_siginfo.si_signo == 0)
> +		return;
>  	/* remove signal */
>  	curthread->deferred_siginfo.si_signo = 0;
>  	handle_signal(&act, info.si_signo, &info, uc);
> 

I can confirm that this also solves the problems I'm seeing.