linux-kernel - Re: [PATCH 0/4] signalfd: a kernel interface for dumping/restoring pending signals

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Message-ID: <CAHO5Pa0B9KsU-kr=M78kRG5WqOf-ere6YmZ0GPUv4WLF6at_RQ@mail.gmail.com>
Date:	Mon, 24 Dec 2012 21:51:10 +0100
From:	Michael Kerrisk <mtk.manpages@...il.com>
To:	Andrey Vagin <avagin@...nvz.org>
Cc:	linux-kernel@...r.kernel.org, criu@...nvz.org,
	linux-fsdevel@...r.kernel.org,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Pavel Emelyanov <xemul@...allels.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Linux API <linux-api@...r.kernel.org>,
	Michael Kerrisk <mtk.manpages@...il.com>
Subject: Re: [PATCH 0/4] signalfd: a kernel interface for dumping/restoring
 pending signals

[CC+=linux-api]

Hi Andrey,

On Mon, Dec 24, 2012 at 9:13 AM, Andrey Vagin <avagin@...nvz.org> wrote:
> The idea is simple. We need to get the siginfo for each signal on dump,
> and then return it back on restore.
>
> The first problem is that the kernel doesn’t report complete siginfo-s
> in user-space. In a signal handler the kernel strips SI_CODE from
> siginfo. When a siginfo is received from signalfd, it has a different
> format with fixed sizes of fields. The interface of signalfd was
> extended. If a signalfd is created with the flag SFD_RAW, it returns
> siginfo in a raw format. We need to choose a queue, so two flags
> SFD_GROUP and SFD_PRIVATE were added.
>
> rt_sigqueueinfo looks suitable for restoring signals, but it can’t send
> siginfo with a positive si_code, because these codes are reserved for
> the kernel. In the real world each person has right to do anything with
> himself, so I think a process should able to send any siginfo to itself.

I see that you CCed me on a couple of the patches in this series.
Thanks for that. But, since most of the series concerns API changes,
it would be good also to CC linux-api on (future revisions of) the
entire series.

I have a few largely cosmetic comments on some of the patches, which
I'll add in the respective threads.

Thanks,

Michael


> Cc: Serge Hallyn <serge.hallyn@...onical.com>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Cc: Pavel Emelyanov <xemul@...allels.com>
> CC: Cyrill Gorcunov <gorcunov@...nvz.org>
>
> --
> 1.7.11.7
>
> --
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-- 
Michael Kerrisk Linux man-pages maintainer;
http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface", http://blog.man7.org/
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