threads/94176: KSE: sigwait doesn't recieve SIGWINCH sent by
pthread_kill() or kill -WINCH
David Xu
davidxu at freebsd.org
Wed Mar 8 02:30:10 GMT 2006
The following reply was made to PR threads/94176; it has been noted by GNATS.
From: David Xu <davidxu at freebsd.org>
To: freebsd-threads at freebsd.org
Cc: john gladkih <john at kak-sam.to>, freebsd-gnats-submit at freebsd.org
Subject: Re: threads/94176: KSE: sigwait doesn't recieve SIGWINCH sent by pthread_kill() or kill -WINCH
Date: Wed, 8 Mar 2006 10:21:09 +0800
On Wednesday 08 March 2006 00:17, john gladkih wrote:
>
> >Number: 94176
> >Category: threads
> >Synopsis: KSE: sigwait doesn't recieve SIGWINCH sent by
pthread_kill() or kill -WINCH
> >Confidential: no
> >Severity: serious
> >Priority: medium
> >Responsible: freebsd-threads
> >State: open
> >Quarter:
> >Keywords:
> >Date-Required:
> >Class: sw-bug
> >Submitter-Id: current-users
> >Arrival-Date: Tue Mar 07 16:20:04 GMT 2006
> >Closed-Date:
> >Last-Modified:
> >Originator: john gladkih
> >Release: 5.4-RELEASE, 5.3-RELEASE
> >Organization:
> >Environment:
> FreeBSD freebsd54.i.drweb.ru 5.4-RELEASE FreeBSD 5.4-RELEASE #0: Sun May 8
10:21:06 UTC 2005
root at harlow.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC i386
>
> >Description:
> sigwait() doesn't recieve SIGWINCH (SIGIO and maybe some others signal) sent
by pthread_kill() from another thread or even from kill -WINCH. there is no
such issue on 5.2.1 and older with libc_r.
Good luck! I have been waiting for this PR for a few years.
The problem you've hit is that default signal action of these signals
is ignore, which causes kernel immediately discard them at the time
the signals are generated, I believe libc_r sets handlers for
these signals, it causes kernel to always deliver these signals to
userland. POSIX does not specify if signal should be discarded immediately
or remain pending if its action is ignore. this means sigwaiting a signal
which action is ignore is not reliable or portable.
http://www.opengroup.org/onlinepubs/000095399/functions/xsh_chap02_04.html
Traditionally, FreeBSD immediately discards a signal if its action is
ignore except that process is being debugged. I am not sure I should
change this history behavior. To work around the problem you've seen,
you can set a dummy action for those signals you want to wait for.
David Xu
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