Re: [RFC c/r 2/4] [RFC] syscalls, x86: Add __NR_kcmp syscall v7

[Cyrill Gorcunov]

On Fri, Jan 27, 2012 at 07:15:25PM +0100, Andi Kleen wrote:
> > It takes up to 5 agruments - the pids of the two tasks (which
> > characteristics should be compared), the comparision type and
> > (in case of comparision of files) two file descriptors.
> 
> Can you please write a manpage for it? That's really required
> to evaluate the interface properly.

Sure, I'll try to (btw, where I should send it to? And in which
format novadays mans are written? In plain old troff or some
human readable asciidocs?) And... should I post man page
on LKML as well?

> 
> As I understand it every time the kernel adds some new kind of state
> this would need to be extended too? This would seem like a lot of work,
> especially since you always need to synchronize kernel/user space.
> How would the user space break if it doesn't know about some newly
> added state?

Wait, maybe I should use kernel-doc here and put comments with example
right on top of SYSCALL definition?

> 
> Maybe it would be better to put more of the relevant code into the
> kernel to encapsulate this better.
> 
> 
> > +	case KCMP_SYSVSEM:
> > +#ifdef CONFIG_SYSVIPC
> > +		ret = kcmp_ptr((long)task1->sysvsem.undo_list,
> > +			       (long)task2->sysvsem.undo_list,
> > +			       KCMP_SYSVSEM);
> 
> I assume that's normally NULL.
> 

Hmm.. Andi, I seem not following. And?

> > +#ifdef CONFIG_X86_64
> > +static long syscall5(int nr, unsigned long arg0, unsigned long arg1,
> > +		unsigned long arg2, unsigned long arg3,
> > +		unsigned long arg4)
> 
> Why not just use syscall() in glibc?
> 

Never heard of it. I'll take a look, thanks. But I suppose all this
comments might be addressed in patch on top?

	Cyrill
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