Messages in this thread | | | Subject | Re: [PATCH] devpts: Sensible /dev/ptmx & force newinstance | From | "H. Peter Anvin" <> | Date | Sat, 19 Dec 2015 20:35:29 -0800 |
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On December 19, 2015 8:11:50 PM PST, ebiederm@xmission.com wrote: >ebiederm@xmission.com (Eric W. Biederman) writes: > >>>> 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)? >> >> I do not believe a fixed association with the first mount is an >> acceptable solution for implementing /dev/ptmx in association with >> a change to cause mount of devpts to be an independent filesystem. >> Such an association fails to be backwards compatible with existing >> userspace, and it is extremely fragile. > >Ugh. After reviewing the userspace code that mounts devpts we have >to do use a magic /dev/ptmx to solve the issue we are trying to solve. > >The fragility of detecting the primary system devpts seems solvable. > >CentOS5 and openwrt-15.05 mount devpts, unmount devpts, >then mount devpts again. So a rule of mouting the internal devpts if >it >isn't mounted would work for those. > >CentOS6 uses switch_root and moves it's early mount of devpts onto the >primary root, and then because devpts is also in /etc/fstab tries and >fails to mount devpts once more at the same location. Implying >newinstance will make that mounting devpts twice. That sounds solvable >but I don't see a clean way of detecting that case yet. > >Ugh. > >I am going to pound my head up against what is needed to find the >primary system mount of devpts for a bit more and see if I can solve >that. Otherwise this exercise is pointless. > >Eric
Does it matter if it mounts devpts twice? It seems like a waste of a minuscule amount of memory, and nothing else. -- Sent from my Android device with K-9 Mail. Please excuse brevity and formatting.
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