Re: [Xen-devel] [PATCH] Fix locking in tools/hotplug/Linux/locking.sh

[Jacek Konieczny <jajcus@xxxxxxxxxx>]

On Mon, Nov 12, 2012 at 07:07:38PM +0100, Olaf Hering wrote:
> On Mon, Nov 12, Ian Campbell wrote:
> 
> > On Fri, 2012-11-09 at 13:56 +0000, Jacek Konieczny wrote:
> > > The claim_lock() function would fail in the perl code with:
> > > 
> > >   Invalid argument at -e line 2.
> > > 
> > > because the Perl snippet opens for reading the file descriptor, which
> > > was earlier opened for write (append).
> > 
> > Looks plausible to me.
> > 
> > How does this interact with the 
> >         eval "exec $_lockfd<&-"
> > which Olaf added in 26079:b3b03536789a ? I suppose close is close and
> > <&- and >&- or even <>&- are equivalent?
> 
> I did not see the perl error, in what environment did you notice this
> error?

Xen 4.2.0

# uname -rm
3.6.6-aos4 x86_64

# perl --version
This is perl, v5.8.8 built for x86_64-pld-linux-thread-multi

I find it a bit strange that it seems to work for everybody else that
me, but the source of my error seems obvious (opening write-only file
descriptor for reading).

I guess my perl, for some reason, does something more when using open()
on an existing file descriptor.

Greets,
        Jacek

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