Re: [PATCH 2 of 4] Introduce i386 fibril scheduling

[Davide Libenzi]

On Mon, 5 Feb 2007, Davide Libenzi wrote:

> On Mon, 5 Feb 2007, Linus Torvalds wrote:
> 
> > Indeed. One word is *exactly* what a normal system call returns too.
> > 
> > That said, normally we have a user-space library layer to turn that into 
> > the "errno + return value" thing, and in the case of async() calls we 
> > very basically wouldn't have that. So either:
> > 
> >  - we'd need to do it in the kernel (which is actually nasty, since 
> >    different system calls have slightly different semantics - some don't 
> >    return any error value at all, and negative numbers are real numbers)
> > 
> >  - we'd have to teach user space about the "negative errno" mechanism, in 
> >    which case one word really is alwats enough.
> > 
> > Quite frankly, I much prefer the second alternative. The "negative errno" 
> > thing has not only worked really really well inside the kernel, it's so 
> > obviously 100% superior to the standard UNIX "-1 + errno" approach that 
> > it's not even funny. 
> 
> Currently it's in the syscall wrapper. Couldn't we have it in the 
> asys_teardown_stack() stub?

Eeeek, that was something *really* stupid I said :D



- Davide


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