CVS commit: src/sys/kern

["Kamil Rytarowski" <kamil%netbsd.org@localhost>]

Module Name:    src
Committed By:   kamil
Date:           Tue Mar 13 02:24:26 UTC 2018

Modified Files:
        src/sys/kern: kern_proc.c

Log Message:
Make sysctl_doeproc() more predictable

Swap the order of looking into zombie and all process lists, start now
with the zombie one. This prevents a race observed previously that the
same process could be detected on both lists during a single polling call.

While there:
 - Short-circuit break for KERN_PROC_PID, once a pid has been detected.
 - Removal of redundant "if (kbuf)" and "if (marker)" checks.
 - Update of comments regarding potential optimization, explaining why we
   don't want to it as of now. Performance gain from lookup call vs
   iteration over a list is neglible on a regular system.
 - Return ESRCH when no results have been found. This allows more easily
   to implement a retry or abandon algorithm.

This corrects races observed in the existing ATF ptrace(2) tests, related
to await_zombie(). This function was expecting to check whether a process
has been transformed into a zombie, however it was causing occasional
crashes as it was overflowing the return buffer, returning the same pid
twice: once from allproc list and the second time from zombieproc one.

Fix suggested by <christos>
Short-circuit break suggested by <kre>

Discussed on tech-kern.

Sponsored by <The NetBSD Foundation>


To generate a diff of this commit:
cvs rdiff -u -r1.210 -r1.211 src/sys/kern/kern_proc.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.