Re: [RESEND][RFC PATCH v2] waitfd

[Casey Dahlin]

Oleg Nesterov wrote:
> On 01/10, Casey Dahlin wrote:
>   
> > Scott James Remnant wrote:
> >     
> > > On Wed, 2009-01-07 at 18:19 +0100, Oleg Nesterov wrote:
> > >
> > >       
> > > > Please note that unlike other sys_...fd() syscalls, sys_waitfd()
> > > > doesn't allow to pass O_CLOEXEC. Looks like we need a separate
> > > > "flags" argument...
> > > >
> > > > Also, ioctl(FIONBIO) or fcntl(O_NONBLOCK) have no effect on
> > > > waitfd, not very good.
> > > >
> > > > I'd suggest to remove WNOHANG from waitfd_ctx->ops and treat
> > > > (->f_flags & O_NONBLOCK) as WNOHANG.
> > > >
> > > > (can't resist, ->ops is not the best name ;)
> > > >
> > > >
> > > >         
> > > Definitely agree here, waitfd() doesn't need WNOHANG - we already have
> > > ONONBLOCK.
> > >
> > > That also solves one of the strangest behaves of waitid when you use
> > > WNOHANG (it returns zero and you have to check whether it changed the
> > > struct), now you just read() - if no child you get EAGAIN, if a child
> > > you read a struct.
> > >
> > >       
> > From the perspective of waitfd, the only difference between WNOHANG and
> > O_NONBLOCK is which argument you put the flags in.
> >     
>
> No. Please see the note about ioctl/fcntl above.
>
> Oleg.
>   
Yes but the actual waitfd call could simply set O_NONBLOCK on the 
descriptor when it receive WNOHANG in the flags, and read the descriptor 
flags going forward.

--CJD
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/