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: Wed, 19 Apr 2017 15:21:34 +0200 Message-ID: <8c7cb5df-bc2f-94d4-0a17-6efdf86f43b3@gmail.com> 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 Hi Christian, Pink on the below! Cheers, Michael On 03/26/2017 02:47 PM, Michael Kerrisk (man-pages) wrote: > 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