On Mon, Sep 23, 2019 at 3:53 AM Florian Weimer <fw@xxxxxxxxxxxxx> wrote: > > * Michael Kerrisk: > > > SYNOPSIS > > int pidfd_open(pid_t pid, unsigned int flags); > > Should this mention <sys/types.h> 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. > > 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. > 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.
