From owner-freebsd-hackers  Tue Apr 17  7:42:26 2001
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Date: Tue, 17 Apr 2001 10:51:48 -0400
From: Dan Eischen <eischen@vigrid.com>
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To: Akinori MUSHA <knu@iDaemons.org>
Cc: deischen@FreeBSD.org, hackers@FreeBSD.org
Subject: Re: bin/25110
References: <86elury85r.wl@archon.local.idaemons.org>
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Akinori MUSHA wrote:
> 
> Hi,
> 
> Would you take a look at PR#25110 ?  Some programs are suffering with
> a problem that with the threaded library a process cannot receive due
> signals except SIGKILL and SIGSTOP from its children and thus it
> stalls at waitpid() after forking.
> 
> The PR precisely describes the underlying cause and points out how you
> can examine and solve the problem.
> 
> I'd appreciate if you or someone else with a clue could deal with it.

You can try the patch below.  I think I've posted this patch before,
but I guess I never committed it.

-- 
Dan Eischen

Index: uthread/uthread_fork.c
===================================================================
RCS file: /opt/b/CVS/src/lib/libc_r/uthread/uthread_fork.c,v
retrieving revision 1.23
diff -u -r1.23 uthread_fork.c
--- uthread/uthread_fork.c	2001/04/10 04:25:49	1.23
+++ uthread/uthread_fork.c	2001/04/17 14:44:37
@@ -32,6 +32,7 @@
  * $FreeBSD: src/lib/libc_r/uthread/uthread_fork.c,v 1.23 2001/04/10 04:25:49 deischen Exp $
  */
 #include <errno.h>
+#include <signal.h>
 #include <string.h>
 #include <stdlib.h>
 #include <unistd.h>
@@ -112,7 +113,16 @@
 		else if (_pq_init(&_readyq) != 0) {
 			/* Abort this application: */
 			PANIC("Cannot initialize priority ready queue.");
-		} else {
+		} else if ((_thread_sigstack.ss_sp == NULL) &&
+		    ((_thread_sigstack.ss_sp = malloc(SIGSTKSZ)) == NULL))
+			PANIC("Unable to allocate alternate signal stack");
+		else {
+			/* Install the alternate signal stack: */
+			_thread_sigstack.ss_size = SIGSTKSZ;
+			_thread_sigstack.ss_flags = 0;
+			if (__sys_sigaltstack(&_thread_sigstack, NULL) != 0)
+				PANIC("Unable to install alternate signal stack");
+
 			/*
 			 * Enter a loop to remove all threads other than
 			 * the running thread from the thread list:

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