Messages in this thread | | | Date | Tue, 19 Apr 2016 20:48:41 -0500 | From | "Serge E. Hallyn" <> | Subject | Re: Does anyone care about a race free ptsname? |
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On Tue, Apr 19, 2016 at 04:39:07PM -0700, H. Peter Anvin wrote: > On 04/19/2016 04:23 PM, Linus Torvalds wrote: > > On Tue, Apr 19, 2016 at 11:44 AM, Eric W. Biederman > > <ebiederm@xmission.com> wrote: > >> > >> I will take a look in a minute. Before I do that I want to mention > >> why I care about /dev/pts/ptmx. > >> > >> There is a posix function that is widely used called ptsname. It's > >> function is to take a master file descriptor and returns the path to the > >> slave. > >> > >> All we have in the kernel to support ptsname is an ioctl TIOCGPTN that > >> returns the pty number in the appropriate instance of devpts. > > > > Don't bother with that completely mis-designed interface.It's crap. > > > > So we'll keep it working for legacy models, but the whole "return an > > integer index" is just pure shit. It's not worth worrying about. > > > > We can (and probably should) just introduce a new ioctl or even a > > system call that just does the sane thing and returns the pathname > > from the kernel. > > > > What do you think of the idea of TIOCPTSOPEN (or whatever) to get a file > descriptor for the slave device given the master device? Then we can
That's what i was thinking, since as I said many users just want
blah = ptsname(fd); slavefd = open(blah, ...);
so they really just want an open fd.
> use realpath() or a readlink on /proc/self/fd/# to get the pathname if > needed. > > (Incidentally, we added getcwd() as a system call. Should we add > [f]realpath() as a system call too?) > > -hpa
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