Re: [PATCH] devpts: Sensible /dev/ptmx & force newinstance

[Peter Hurley]

On 12/11/2015 11:40 AM, Eric W. Biederman wrote:
> Forcing newinstance for every mount of the devpts filesystem actually
> requires the association between /dev/ptmx and the currently mounted
> instance of devpts at /dev/pts.  Simply remembering the first mount of
> the devpts filesystem and associating that with /dev/ptmx is not
> enough.  I am aware of at least one instance where an initramfs mounts
> devpts before the main system instance of devpts is mounted.

Can you point me to that usage please?

I ask because there's a patch to move devpts init from module initcall
up to fs initcall (neither devpts nor the pty driver is actually built
as a module anyway), and I'd like to look at what the consequences
might be for that userspace configuration.


> In that system ptys simply did not work after boot when I tested
> associating /dev/ptmx with the first mount of the devpts filesystem.

Assuming userspace isn't broken by that patch, is a fixed association
with first mount otherwise an acceptable solution for magic /dev/ptmx
(where /dev/ptmx is not a symlink to /dev/pts/ptmx)?

Regards,
Peter Hurley

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