Re: For review: pidfd_send_signal(2) manual page

[Daniel Colascione]

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 termiâ
>        nated  and its PID has been recycled for another process.  By conâ
>        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".