From: Christoph Rohland <cr@sap.com>
To: Paul Menage <pmenage@ensim.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH][RFC] Pollable /proc/<pid>/ - avoid SIGCHLD/poll() races
Date: 04 Oct 2001 10:59:07 +0200 [thread overview]
Message-ID: <m34rpfpyqs.fsf@linux.local> (raw)
In-Reply-To: <E15p3JS-0000ko-00@pmenage-dt.ensim.com>
In-Reply-To: <E15p3JS-0000ko-00@pmenage-dt.ensim.com>
Hi Paul,
On Thu, 04 Oct 2001, Paul Menage wrote:
>
> I've recently run across a problem where a server (in this case,
> sshd) can deadlock itself if a SIGCHLD arrives just before it calls
> select(), but after it has checked whether its child_terminated. So
> when the select() is called, the SIGCHLD signal handler has already
> run and set the child_terminated flag, and there's nothing to wake
> the select().
>
> The only real user-space solution to this is to have the SIGCHLD
> handler somehow cause the select() to return immediately
... or implement pselect:
http://mesh.eecs.umich.edu/cgi-bin/man2html/usr/share/man/man2/select.2.gz
or use sigsetjmp/siglongjmp
Both would be portable and not special to child handling.
Greetings
Christoph
next prev parent reply other threads:[~2001-10-04 8:59 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-10-04 7:52 [PATCH][RFC] Pollable /proc/<pid>/ - avoid SIGCHLD/poll() races Paul Menage
2001-10-04 8:59 ` Christoph Rohland [this message]
2001-10-04 9:31 ` Paul Menage
2001-10-04 10:25 ` Christoph Rohland
2001-10-13 15:44 ` Jamie Lokier
2001-10-04 14:18 ` Mattias Engdegård
2001-10-04 20:39 ` Paul Menage
2001-10-05 9:36 ` Mattias Engdegård
2001-10-13 15:36 ` Jamie Lokier
2001-10-14 2:25 ` John Alvord
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