Re: light weight user level semaphores

[Abramo Bagnara <abramo@alsa-project.org>]

Linus Torvalds wrote:
> 
> On Thu, 19 Apr 2001, Abramo Bagnara wrote:
> >
> > > [ Using file descriptors ]
> >
> > This would also permit:
> > - to have poll()
> > - to use mmap() to obtain the userspace area
> >
> > It would become something very near to sacred Unix dogmas ;-)
> 
> No, this is NOT what the UNIX dogmas are all about.
> 
> When UNIX says "everything is a file", it really means that "everything is
> a stream of bytes". Things like magic operations on file desciptors are
> _anathema_ to UNIX. ioctl() is the worst wart of UNIX. Having magic
> semantics of file descriptors is NOT Unix dogma at all, it is a horrible
> corruption of the original UNIX cleanlyness.

Nice outpouring indeed, it seems taken from L'Ouvre au Noir by
Marguerite Yourcenar ;-)))

You're perfectly right but the file descriptor solution appeared to me a
nice way to work around the Unix limitation to have poll(2) working only
on file descriptor.

Said this, I've no doubt that a better poll-like syscall would solve all
that in a more elegant way.

You understand that sometime we've no other choice that to design
workarounds to minimize needed changes (and then often to maximize
acceptance probability).

OTOH you may always decide to do things in the elegant way, you've such
a responsibility for linux kernel.

-- 
Abramo Bagnara                       mailto:abramo@alsa-project.org

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It sounds good!