Re: [Xen-devel] [PATCH 1/3] Revert "tools/libxl: Adjust datacopiers POLLHUP handling when the fd is also readable"

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Ian Campbell writes ("Re: [PATCH 1/3] Revert "tools/libxl: Adjust datacopiers 
POLLHUP handling when the fd is also readable""):
> On Thu, 2015-04-02 at 16:04 +0100, Ian Jackson wrote:
> > The bootloader code is relying on detecting POLLHUP, and 7e9ec50b
> > breaks that.  7e9ec50b, when handling a pty master, violates the
> > specification of the datacopier interface (as defined).
> > 
> > When the bootloader exits, several things change, all at once:
> >  (a) The master pty fd (held by libxl) starts to signal POLLHUP
> >     and maybe also POLLIN.
> >  (b) The child exits (so that the SIGCHLD self-pipe signals POLLIN,
> >     which will be handled by the libxl child process code.
> >  (c) reads on the master pty fd start to return EOF
> > 
> > From the point of view of the datacopier these might happen in any
> > order.  I think there is a latent bug with (c), which I will discuss
> > later in this email.
> 
> later in another mail maybe?

In 3/3.  Oh well, I have pushed it now.

Thanks,
Ian.

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