Re: [Linuxptp-users] Fw: “Resource temporarily unavailable” errors during flood ping test

[Keller, J. E <jac...@in...>]

> -----Original Message-----
> From: Miroslav Lichvar [mailto:mli...@re...]
> Sent: Tuesday, October 30, 2012 10:17 AM
> To: lin...@li...
> Subject: Re: [Linuxptp-users] Fw: “Resource temporarily unavailable”
> errors during flood ping test
> 
> On Tue, Oct 30, 2012 at 06:05:38PM +0100, Richard Cochran wrote:
> > This does not accomplish anything since:
> >
> > --- /usr/include/asm-generic/errno.h ---
> >
> > #define	  EWOULDBLOCK	 EAGAIN	  /* Operation would block */
> >
> >
> > >   			usleep(1);
> > >  +			try_again++;
> >
> > This is the wrong solution. The right way is to set the
> > tx_timestamp_retries configuration variable to a higher number, like
> > 200 or 2000 instead of the default of 2.
> 
> Would it make sense to specify a timeout instead of number of retries
> and use select()?
> 
> --
> Miroslav Lichvar

I did some digging in the kernel to figure out why exceptfs parameter didn't get wokenup when a message appeared on the error queue. Turns out that is because in fs/socket.c the POLLEX_SET flags only includes POLL_PRI and not POLL_ERR. I tried a modified kernel which defined POLLEX_SET (POLL_PRI | POLL_ERR) and it enabled the usecase we want. Sadly this would add a further dependency.. and probably can't really be changed..

I don't know why exceptfs which is documented as "wake a socket on error" doesn't check POLL_ERR flag.... it seems really silly.

- Jake