linux-kernel - Re: Fix signalfd interaction with thread-private signals

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Date:	Fri, 22 Jun 2007 20:04:06 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Davide Libenzi <davidel@...ilserver.org>,
	Nicholas Miell <nmiell@...cast.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Fix signalfd interaction with thread-private signals

On 06/22, Benjamin Herrenschmidt wrote:
> 
> That is, it -does- make sense to be able to create a signal singalfd in
> a process and have N threads reading from it and getting either shared
> signals or their local private signals.

Great.

> I just don't like the actual implementation of it by changing the task
> pointer on the fly...
>
> My main issue is a matter of consistency of the signalfd API as a
> whole... the whole bloody thing is instanciated & attached to a thread
> in the first place. Maybe we should change that and say that one
> instanciates a signalfd on a thread group... that is, it always gets
> attached to the leader.

It does exactly so, please note this chunk

 @@ -330,7 +339,7 @@ asmlinkage long sys_signalfd(int ufd, si

                 init_waitqueue_head(&ctx->wqh);
                 ctx->sigmask = sigmask;
 -               ctx->tsk = current;
 +               ctx->tsk = current->group_leader;

> It might well be that signalfd's concept of context is wrong in the
> first place and it should be attached to processes rather than threads
> and that made more explicit in the first place...

Exactly!

Oleg.

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