Document /proc/pid PID reuse behavior

State explicitly that holding a /proc/pid file descriptor open does
not reserve the PID. Also note that in the event of PID reuse, these
open file descriptors refer to the old, now-dead process, and not the
new one that happens to be named the same numeric PID.

Signed-off-by: Daniel Colascione <dancol@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Daniel Colascione 2018-11-05 13:22:05 +00:00 committed by Jonathan Corbet
parent 1428cc0e0c
commit c969eb8301
1 changed files with 7 additions and 0 deletions

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@ -125,6 +125,13 @@ process running on the system, which is named after the process ID (PID).
The link self points to the process reading the file system. Each process The link self points to the process reading the file system. Each process
subdirectory has the entries listed in Table 1-1. subdirectory has the entries listed in Table 1-1.
Note that an open a file descriptor to /proc/<pid> or to any of its
contained files or subdirectories does not prevent <pid> being reused
for some other process in the event that <pid> exits. Operations on
open /proc/<pid> file descriptors corresponding to dead processes
never act on any new process that the kernel may, through chance, have
also assigned the process ID <pid>. Instead, operations on these FDs
usually fail with ESRCH.
Table 1-1: Process specific entries in /proc Table 1-1: Process specific entries in /proc
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