Re: [PATCH] bug in setpgid()? process groups and thread groups

From: Alan Cox (alan@lxorguk.ukuu.org.uk)
Date: Sun Aug 03 2003 - 16:00:24 EST


On Sul, 2003-08-03 at 08:22, Florian Weimer wrote:
> Alan Cox <alan@lxorguk.ukuu.org.uk> writes:
>
> > #1 Lots of non posix afflicted intelligent programmers use the per
> > thread uid stuff in daemons. Its really really useful
>
> It doesn't work reliably because the threading implementation might
> have to send signals which the current combination of credentials does
> not allow.

It works beautifully. Its very effective for clone() using applications

> IMHO, POSIX is wrong to favor process attributes so strongly. It
> wouldn't be a problem if there were other ways to pass these implicit
> parameters (such as thread-specific attributes, or, even better,
> syscall arguments). But often there isn't.

The restriction in this case comes from a more fundamental thing - posix pthreads
is full of compromises so it can be done in user space. Clearly you can't split
uid's in user space very sanely.

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