linux-kernel - signalfd() semantics after execve()

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Message-ID: <20070714074145.277260@gmx.net>
Date:	Sat, 14 Jul 2007 09:41:45 +0200
From:	"Michael Kerrisk" <mtk-manpages@....net>
To:	Davide Libenzi <davidel@...ilserver.org>
Cc:	linux-kernel@...r.kernel.org
Subject: signalfd() semantics after execve()

Davide, 

I'm working on the signalfd(2) man page, and I've come
acorss some puzzling behaviour...  

What are the intended semantics of a signalfd file descriptor
after an execve()?

As far as I can work out, after an execve() the file descriptor
is still available, but reads from it always return 0, even if:

a) there were signals pending before the execve().
   However, sigpending() shows the signal as pending,
   and the signal can be accepted using sigwaitinfo().

b) we generate a signal after the execve().

Is this intended behavior (the "orphaned sighand" condition
mentioned in the draft man page you sent me?)?  Is it a bug?

Cheers,

Michael

-- 
Michael Kerrisk
maintainer of Linux man pages Sections 2, 3, 4, 5, and 7 

Want to help with man page maintenance?  
Grab the latest tarball at
http://www.kernel.org/pub/linux/docs/manpages , 
read the HOWTOHELP file and grep the source 
files for 'FIXME'.

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