On 08/03, Peter Zijlstra wrote:
>
> On Mon, 2009-08-03 at 19:16 +0200, Oleg Nesterov wrote:
>
> > Hmm, OK. so fcntl(F_SETOWN_TID, -666) <=> fcntl(F_SETOWN, +666).
> >
> > Not that I disagree, but I think this should be discussed. Perhaps
> > F_SETOWN_TID can just reject who < 0.
>
> Yeah, I considered that. Opinions?
Yes, please ;)
> > but the caller of F_GETOWN can't know what the returned value actually
> > means if F_GETOWN_TID was used.
>
> Ah, I made GETOWN_TID deal with !PID but forgot the TID case in GETOWN.
> Yeah, icky, esp since there is no room for errors in the return value :/
> I guess I could make it return 0.
Yes, this is confusing too, but probably better.
> > Perhaps we can just add
> >
> > #define F_PIDTYPE_THREAD PIDTYPE_MAX
> >
> > into fcntl.c ? Then,
> >
> Right, I considered adding PIDTYPE_TID, but then I'd have to go through
> the kernel and make everything consistent, which is where I gave up ;-)
Note! we don't add the new PIDTYPE_TID actually. This F_PIDTYPE_THREAD
is not visible outsie of fcntl.c, we just re-use ->pid_type. Instead
we could add a bit, but using the impossible PIDTYPE_MAX is simpler.
> dunno if people will go for it though..
Yes, I am not sure people will like it.
As for F_XXXOWN/F_XXXWOWN_TID interaction. Another option, perhaps, is add
F_{SET,GET}OWN_EX which accepts a use-visible
struct f_setown_struct {
int pid; // > 0
int type; // enumerates PIDTYPE_PID,
PIDTYPE_PGID, F_PIDTYPE_THREAD
}
pointer via arg. Instead of F_XXXOWN_TID + int who.
This way at least the users of new api can't be confused.
I dunno.
Oleg.
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