Xen devel - Aug 2007 - Re: [Xen-changelog] [xen-unstable] xenstored: Do not write to stderr if we are daemonised!

On Wed, Aug 01, 2007 at 09:53:17AM -0700, Xen patchbot-unstable wrote:
> +
> +		/* Get ourselves a nice xenstored crash if these are used. */
> +		stdin = NULL;
> +		stdout = NULL;
> +		stderr = NULL;
You cannot assign to std* on Solaris, this becomes:

 (&__iob[0]) = 0;
 (&__iob[1]) = 0;
 (&__iob[2]) = 0;

which obviously won''t compile.

regards,
john

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On 1/8/07 19:03, "John Levon" <levon@movementarian.org> wrote:
>> +
>> +  /* Get ourselves a nice xenstored crash if these are used. */
>> +  stdin = NULL;
>> +  stdout = NULL;
>> +  stderr = NULL;
> 
> You cannot assign to std* on Solaris, this becomes:
> 
>  (&__iob[0]) = 0;
>  (&__iob[1]) = 0;
>  (&__iob[2]) = 0;
> 
> which obviously won''t compile.
Okay, I''ll fix this by redirecting xprintf() to trace() and get rid of
the
NULL assignments.

 -- Keir


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On Wed, Aug 01, 2007 at 07:03:23PM +0100, John Levon
wrote:
> On Wed, Aug 01, 2007 at 09:53:17AM -0700, Xen patchbot-unstable wrote:
> 
> > +
> > +		/* Get ourselves a nice xenstored crash if these are used. */
> > +		stdin = NULL;
> > +		stdout = NULL;
> > +		stderr = NULL;
> 
> You cannot assign to std* on Solaris, this becomes:
> 
>  (&__iob[0]) = 0;
>  (&__iob[1]) = 0;
>  (&__iob[2]) = 0;
> 
> which obviously won''t compile.
Yep, rather than closing FD''s and setting the FILE* to NULL, the daeon
code should re-open /dev/null for stdin/out/err which is the traditional
approach for most UNIX daemons.

        if (dofork) {
                int devnull;
                devnull = open(_PATH_DEVNULL, O_RDWR);
                close(STDIN_FILENO);
                close(STDOUT_FILENO);
                close(STDERR_FILENO);
                dup2(devnull, STDIN_FILENO);
                dup2(devnull, STDOUT_FILENO);
                dup2(devnull, STDERR_FILENO);
                close(devnull);
        }

(With error checking on open/close/dup2 of ccourse)

Regards,
Dan.
-- 
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On Wed, Aug 01, 2007 at 07:12:22PM +0100, Keir Fraser wrote:
> > You cannot assign to std* on Solaris, this becomes:
> > 
> >  (&__iob[0]) = 0;
> >  (&__iob[1]) = 0;
> >  (&__iob[2]) = 0;
> 
> Okay, I''ll fix this by redirecting xprintf() to trace() and get
rid of the
> NULL assignments.
Thanks!

BTW, you mentioned a new 3.1 release some time soon. Is there something
we can usefully be doing to help this happen? (Certainly me doing some
testing of 3.1 at all would help...)

The bug fixes I care most about offhand are the ones that finish
implementing the xen api.

regards,
john

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Good idea. Can''t use _PATH_DEVNULL easily though, since it''ll
break Solaris
again (no paths.h). Hardcoding /dev/null is not so bad -- the console daemon
does this already.

 -- Keir

On 1/8/07 19:20, "Daniel P. Berrange" <berrange@redhat.com>
wrote:
> Yep, rather than closing FD''s and setting the FILE* to NULL, the
daeon
> code should re-open /dev/null for stdin/out/err which is the traditional
> approach for most UNIX daemons.
> 
>         if (dofork) {
>                 int devnull;
>                 devnull = open(_PATH_DEVNULL, O_RDWR);
>                 close(STDIN_FILENO);
>                 close(STDOUT_FILENO);
>                 close(STDERR_FILENO);
>                 dup2(devnull, STDIN_FILENO);
>                 dup2(devnull, STDOUT_FILENO);
>                 dup2(devnull, STDERR_FILENO);
>                 close(devnull);
>         }

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On Wed, Aug 01, 2007 at 07:32:59PM +0100, Keir Fraser wrote:
> Good idea. Can''t use _PATH_DEVNULL easily though, since
it''ll break Solaris
> again (no paths.h). Hardcoding /dev/null is not so bad -- the console
daemon
> does this already.
I''m somewhat bemused as to the purpose of _PATH_DEVNULL - is this
different on Hurd or something?

regards
john

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> Okay, I''ll fix this by redirecting xprintf() to trace() and get
rid of the
> NULL assignments.
You are guaranteed to be able to freopen() stdin/stdout/stderr and that
is a portable C feature. This means you can divert the stdin/out/err to a
log file to catch such accidents or at least avoid future problems by
firing them down /dev/null.


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