From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael Kerrisk (man-pages)" Subject: Re: For review: pidfd_open(2) manual page Date: Mon, 23 Sep 2019 22:22:22 +0200 Message-ID: <39790bc7-f417-1172-0f06-5cdefabda7e1@gmail.com> References: <90399dee-53d8-a82c-3871-9ec8f94601ce@gmail.com> <87tv939td6.fsf@mid.deneb.enyo.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Daniel Colascione , Florian Weimer Cc: mtk.manpages@gmail.com, Christian Brauner , Jann Horn , "Eric W. Biederman" , Joel Fernandes , Linux API , lkml , linux-man , Oleg Nesterov List-Id: linux-api@vger.kernel.org Hello Daniel, Than you for reviewing the page! On 9/23/19 1:26 PM, Daniel Colascione wrote: > On Mon, Sep 23, 2019 at 3:53 AM Florian Weimer wrote: >> >> * Michael Kerrisk: >> >>> SYNOPSIS >>> int pidfd_open(pid_t pid, unsigned int flags); >> >> Should this mention for pid_t? >> >>> ERRORS >>> EINVAL flags is not 0. >>> >>> EINVAL pid is not valid. >>> >>> ESRCH The process specified by pid does not exist. >> >> Presumably, EMFILE and ENFILE are also possible errors, and so is >> ENOMEM. >> >>> A PID file descriptor can be monitored using poll(2), select(2), >>> and epoll(7). When the process that it refers to terminates, the >>> file descriptor indicates as readable. > > The phrase "becomes readable" is simpler than "indicates as readable" > and conveys the same meaning. I agree with Florian's comment on this > point below. See my reply to Florian. (I did change the text here.) >>> Note, however, that in the >>> current implementation, nothing can be read from the file descrip‐ >>> tor. >> >> “is indicated as readable” or “becomes readable”? Will reading block? >> >>> The pidfd_open() system call is the preferred way of obtaining a >>> PID file descriptor. The alternative is to obtain a file descrip‐ >>> tor by opening a /proc/[pid] directory. However, the latter tech‐ >>> nique is possible only if the proc(5) file system is mounted; fur‐ >>> thermore, the file descriptor obtained in this way is not pol‐ >>> lable. > > Referring to procfs directory FDs as pidfds will probably confuse > people. I'd just omit this paragraph. See my reply to Christian (and feel free to argue the point, please). So far, I have made no change here. >> One question is whether the glibc wrapper should fall back back to the >> /proc subdirectory if it is not available. Probably not. > > I'd prefer that glibc not provide this kind of fallback. > posix_fallocate-style emulation is, IMHO, too surprising. Agreed. Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/