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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