Re: [Xen-devel] [PATCH] Fix xenconsole's "Could not read tty from store"

[Samuel Thibault <samuel.thibault@xxxxxxxxxxxxx>]

John Levon, le Tue 18 Dec 2007 18:13:53 +0000, a écrit :
> On Tue, Dec 18, 2007 at 06:07:17PM +0000, Samuel Thibault wrote:
> 
> > > > +       if (tcgetattr(master, &term) < 0) {
> > > > +               err = errno;
> > > 
> > > Please use the slave not the master. It doesn't matter on Linux but it's
> > > critical on Solaris.
> > 
> > What is the Solaris reason for this?  It really looks we can't afford
> > closing the slave end on Linux (hence leak it) or not open it at all
> > (and then we can't tcgetattr on it).
> 
> On Linux, both ends of a pty act like a pseudo-terminal and you can do
> term-like things on both ends (and there's apparently small variations
> in the effect they have). This is not true on STREAMS-based systems. In
> particular, you have to push the "ptem" module before you can use any of
> the tcget/setattr() functions (look at openpty()).

I'm precisely reading that part of the sun manual thanks to google, yes
:)

Can't we push those modules on such systems?

> I'm working on a new version of the patch that just keeps the slave open
> (without leaking it) on both platforms - I think this should cover these
> differences sufficiently.

Well, there should be no reason to open the slave part at all, actually.
To my understanding, from the server side tcsetattr should only be
performed on the master side (with effect on the slave side too).

Samuel

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