On 9/23/19 1:31 PM, Daniel Colascione wrote: > On Mon, Sep 23, 2019 at 2:12 AM Michael Kerrisk (man-pages) > <mtk.manpages@xxxxxxxxx> wrote: >> The pidfd_send_signal() system call allows the avoidance of race >> conditions that occur when using traditional interfaces (such as >> kill(2)) to signal a process. The problem is that the traditional >> interfaces specify the target process via a process ID (PID), with >> the result that the sender may accidentally send a signal to the >> wrong process if the originally intended target process has termi‐ >> nated and its PID has been recycled for another process. By con‐ >> trast, a PID file descriptor is a stable reference to a specific >> process; if that process terminates, then the file descriptor >> ceases to be valid > > The file *descriptor* remains valid even after the process to which it > refers exits. You can close(2) the file descriptor without getting > EBADF. I'd say, instead, that "a PID file descriptor is a stable > reference to a specific process; process-related operations on a PID > file descriptor fail after that process exits". Thanks, Daniel. I like that rephrasing, but, since pidfd_send_signal() is (so far as I know) currently the only relevant process-related operation (and because this is the manual page describing that syscall), I made it: [[ By contrast, a PID file descriptor is a stable reference to a specific process; if that process terminates, pidfd_send_signal() fails with the error ESRCH. ]] Thanks, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
