From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael Kerrisk (man-pages)" Subject: Re: [PATCH] ttyname.3: document ENODEV error code Date: Sun, 26 Mar 2017 14:47:32 +0200 Message-ID: References: <20170320205104.GA27434@altlinux.org> <20170320215823.GA28075@altlinux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-man-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Christian Brauner Cc: mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, "Dmitry V. Levin" , linux-man-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Serge Hallyn , =?UTF-8?Q?St=c3=a9phane_Graber?= List-Id: linux-man@vger.kernel.org On 03/24/2017 03:53 PM, Christian Brauner wrote: > Sorry, for the late reply. > > On Fri, Mar 24, 2017 at 3:40 PM, Michael Kerrisk (man-pages) > wrote: >> Hi Dmitry, >> >> On 03/20/2017 10:58 PM, Dmitry V. Levin wrote: >>> Hi, >>> >>> On Mon, Mar 20, 2017 at 10:02:15PM +0100, Christian Brauner wrote: >>>> Hi, >>>> >>>> Thanks Dmitry. One comment >>>> >>>> On 20 Mar 2017 9:51 p.m., "Dmitry V. Levin" wrote: >>>> >>>> --- >>>> man3/ttyname.3 | 8 +++++++- >>>> 1 file changed, 7 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/man3/ttyname.3 b/man3/ttyname.3 >>>> index 14c24e7..0be50c6 100644 >>>> --- a/man3/ttyname.3 >>>> +++ b/man3/ttyname.3 >>>> @@ -71,6 +71,11 @@ File descriptor does not refer to a terminal device. >>>> .RB ( ttyname_r ()) >>>> .I buflen >>>> was too small to allow storing the pathname. >>>> +.TP >>>> +.\" glibc commit 15e9a4f378c8607c2ae1aa465436af4321db0e23 >>>> +.B ENODEV >>>> +File descriptor refers to a slave pseudoterminal device >>>> +but the corresponding pathname could not be found. >>>> >>>> I think it would be good to explicitly mention that ENODEV is set in case >>>> the fd does not refer to a pts device in its namespace. Otherwise users >>>> might take this as an indication that this is a more generic error which is >>>> not the case. >>> >>> In fact, this is a more generic error than a namespace mismatch, although >>> the latter is the most likely reason. >>> >>> Imagine that the corresponding file inside /dev/pts/ is not available for >>> some reason and the stat call has failed. This situation could be >>> reproduced e.g. by bind-mounting an empty directory to /dev/pts. >>> A subsequent ttyname invocation would end up with ENODEV because the device >>> is literally not available although it's withing the same namespace. >>> >>> I don't mind if you change the description to mention the namespace case >>> as the most likely, but please do not make it the only case when ENODEV >>> can happen. >> >> I'm open on this point. If someone wants to write a suitable patch, I'll >> probably take it. > > This point is in my opinion crucial. The over-mounting scenario is > still a valid case for most programs that do not actually care about > what /dev/pts/ is actually used to go on which is a nice side-effect > of the patch. The namespace part should be mentioned since ttyname{_r}() > explicitly does not return anything when it detects that > /proc/self/fd/ points to /dev/pts/ but /dev/pts/ does not exist > in the same namespace. This was the original motivation when we > wrote the patch. So users that get ENODEV from ttyname{_r}() should > be aware that resolving the symlink manually afterwards doesn't give them > a /dev/pts/ path valid in the current namespace. > > I'll put this on my TODO list but if someone is willing to send a > patch right away > please do so. :) Hi Christian, I think you may be best placed to know what you want to convey here. I'd be happy to receive a patch. Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html