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Date: Mon, 18 Nov 2002 00:21:26 -0800
From: Ulrich Drepper <drepper@redhat.com>
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To: Luca Barbieri <ldb@ldb.ods.org>
CC: Linus Torvalds <torvalds@transmeta.com>, Ingo Molnar <mingo@elte.hu>,
       Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [patch] threading fix, tid-2.5.47-A3
References: <Pine.LNX.4.44.0211172003050.1206-100000@home.transmeta.com> <1037606831.1774.13.camel@ldb>
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Luca Barbieri wrote:

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> There are: suppose that you want to implement the int cfork(int* pid)
> function, which returns the pid in *pid in the parent vm, in a
> multithreaded application.

Correct, for a cfork() implementation two separate pointers would be
needed.  Ingo was asking the same question.

Note that I haven't received a request for such a fork interface variant
yet.  There obviously is a problem with fork() in MT apps but people are
either not hitting it or working around it.  In any case, cfork() would
at least for the time being Linux-specific anyway.


If people are in fact interested in such a new interface then you should
start asking Linus to change his mind on the second parameter.  I'm at
this point in time neutral since there is no urgent need from my
perspective to implement cfork(),

> You could avoid the additional pointer by letting
> child_tidptr = (!(flags & CLONE_VM) && current->user_tid) ?
> current->user_tid : parent_tidptr;

This doesn't work since it would overwrite the TID field in the calling
thread's descriptor.

- -- 
- --------------.                        ,-.            444 Castro Street
Ulrich Drepper \    ,-----------------'   \ Mountain View, CA 94041 USA
Red Hat         `--' drepper at redhat.com `---------------------------
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