Re: [PATCH] 'select' failure or signal should not update timeout

[Christoph Rohland]

Hi Linus,

On Sat, 20 Jul 2002, Linus Torvalds wrote:
> The thing is, nobody should really ever use timeouts, because the
> notion of "I want to sleep X seconds" is simply not _useful_ if the
> process also just got delayed by a page-out event as it said so.
> What does "X seconds" mean at that point? It's ambiguous - and the
> kernel will (quite naturally) just always assume that it is "X
> seconds from when the kernel got notified".
>
> A _useful_ interface would be to say "I want to sleep to at most
> time X" or "to at least time X".  Those are unambiguous things to
> say, and are not open to interpretation.

Yes, so everybody really using select assumes it's _at least_ X
seconds... So where's the problem? I always know it's at least in a
multiprocess environment. (At least as long as I do not want to fiddle
with scheduling and priorities)

> The Linux behaviour of modifying the timeout is a half-assed try for
> restartability, but the problem is that (a) nobody else does that or
> expects it to happen, despite the man-pages originally claiming that
> they were supposed to and (b) it inherently has rounding problems
> and other ambiguities - making it even less useful.

Yes, and probably select is one of the calls you most of the time use
because of portability. So IMHO a linuxism isn't worth the effort.

Greetings
		Christoph