linux-kernel - Re: [patch 0/3] add rt_tgsigqueueinfo syscall [RESEND]

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Message-ID: <cfd18e0f0902280046k3171c97uaf9d984bd7894e82@mail.gmail.com>
Date:	Sat, 28 Feb 2009 21:46:35 +1300
From:	Michael Kerrisk <mtk.manpages@...glemail.com>
To:	Roland McGrath <roland@...hat.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...sign.ru>, Ingo Molnar <mingo@...e.hu>,
	Linux API <linux-api@...r.kernel.org>, drepper@...hat.com
Subject: Re: [patch 0/3] add rt_tgsigqueueinfo syscall [RESEND]

On 2/28/09, Roland McGrath <roland@...hat.com> wrote:
>> With respect to the first point, it seems to me reasonably likely that
>> there would be use cases where the receiving thread wants to know the
>> thread ID of the sender -- especially when sender and receiver are in
>> the same process.
>
> But expecting si_pid to play that role is bizarre.

Oh -- I wasn't suggeting that si_pid do that task; I was instead
wondering if we needed an additional si_threadid field (or some such).

> It's never what any
> POSIX-like program would do, both since POSIX says si_pid is a process ID,
> and because there are no POSIX-like interfaces at all that use Linux TIDs
> to refer to threads.

(Nod.)

> Wanting this only seems plausible within one process.

We are in agreement.

> In that case, sender
> and recipient know they share memory.  The normal thing to do (and what
> POSIX applications will do) is to store that info somewhere pointed to by
> the sigval.

Good point.  That would be another of dealing with point I wondered
about, and probably better than my idea.

Cheers,

Michael

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
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